Diary of the RuralZED building course

Below is a day-by-day account of Sustainable Penwith's participation in the RuralZED course run by Cornwall Sustainable Building Trust over a 10-week period at the disused Holman's factory in Camborne.

The design was the winner of the CSBT's ANSAS competition (A Novel Sustainable Affordable Solution) to Cornwall's housing problems.

See www.zedfactory.com and /www.bedzed.org.uk for more

The project manager for the build is Joe Fenn of Optimal Construction and his sons, Rob and Lewis, are the carpenters bringing with them previous experience of timber construction.

(Digital camera courtesy of Ruth and Dave)

Index

Introduction Day

Day 1: "The Footings"

Day 2: "The Glue Lambs"

Day 3: "Out of the ground"

Day 4: "To crane or not to crane?"

Day 5: "Floored"

Day 6: "Strutting and decking"

Day 7: "Firewall and noggins"

Day 8: "Like Lego, only heavier!"

Day 9: "Concrete juggle"

Day 10: "House!"

Final Week

Expo Day

Photo Slideshow (or click on the small images below in the text)

Introduction Day

I have attended the first day of a Cornwall Sustainable Building Trust course on building a "ZED" (Zero Emission Development) house as designed by Bill Dunster architects, which is closely related to the development in London known as BedZED.

The 10-week, one-day-a-week course serves as an instruction course on how to erect a flat pack eco-home, with carefully chosen materials and practices, resulting in a house which requires only 50% of the energy of an average home and which produces all that energy from passive solar gain, integral solar water heating, photovoltaic and wind turbine. A trademark wind cowl on the roof directs fresh air down into the house through an 85% efficient heat exchanger which warms the incoming air with heat extracted from expelled stale air. This cuts down on the need for space heating. Indeed, the house has no central heating relying solely on the passive solar and heat recovery ventilation.

The house is built on reclaimed railway sleepers on a bed of compacted recycled aggregate. It is essentially a timber frame construction with a breathable but airtight membrane to seal the house leaving the heat exchanger to ventilate the house. The principal design has a southerly facing atrium which provides passive solar heating in winter and acts as a temperature buffer in summer.

The contentious inclusion of prefab concrete panels to provide the walls and floors is necessary to build in "thermal mass" which helps to passively regulate the temperature in the house - keeping it cool in summer, and warm in winter. (A super-insulated 'lightweight' house of simple timber construction needs power hungry air-conditioning in summer, though in Scandinavia this can work since they rarely get hot summers - the converse is that most Spanish houses are 'heavy' using thermal mass to moderate intense summer temperatures) The concrete panels are made from recycled aggregate with a china clay production waste product.

The 8m x 10m houses are built around a 2m grid system allowing simple room division and possible future internal re-organisation including conversion for wheelchair use. Wiring and plumbing run in conduits and channels that make moving fixings easier than a conventional house. The roof is covered in a low-maintenance, drought-resistant grass type plant that can be grown off-site and then rolled up to be put in place, helping to slow rainwater run-off.

The 18 or so students will collectively build this prototype in the redundant Holmans factory at Camborne which will be available as a show house for one day only using it as a test-bed for Dunster & co to refine the flat pack design and identify the pitfalls etc.

Once finalised, prospective purchasers will need to attend (and pass) future courses to qualify to purchase the house building kit against which the cost of the course will be refunded and will include telephone help and advice throughout the build.

Day 1: "The Footings"

What looked like being rather a dull day just moving railway sleepers around turned out to be interesting and challenging after all. We were first issued with steel toe-capped boots, bright orange gloves with incredibly sticky rubber palms that must rival Spiderman for clingability, high-visibility vests and the obligatory hard hat. Our project manager Joe took us through some "health & safety" principles for manual lifting to make sure that we don't hurt ourselves or each other. These briefings will be a feature of each work day since different stages of the build will bring different hazards and considerations.

We first learned how to mark out the building 'plot' with strings. From a baseline (your chosen reference line, usually the front or back wall of the house) we ran strings at 90 degrees, 8 metres apart to delimit the sides of the house. This uses the 3-4-5 method a.k.a. Pythagoras' theorem - that a right-angled triangle with the two shorter sides of 3 units (metres, feet or whatever) and 4 units respectively will give a diagonal (hypotenuse) of 5 units. For greater accuracy we also doubled up the distances to get a 6-8-10 rule. We then added the "back wall" and repeated the procedure.

After some tweaking we got it "square"! The diagonals (measured across opposite corners) were then within an acceptable tolerance. On a real plot the strings would have been attached to stakes driven into the ground but since we thought that we shouldn't go driving things into the factory floor we relied on wrapping the strings around breeze blocks!

The ZED design encapsulates one of the basic principles of sustainability of reducing transport distances by sourcing as many materials from as close to home as possible.

The footings of the houses will be 6 trenches, each about 8 metres long, filled with compact recycled hardcore, a plentiful waste product from the conventional construction industry available virtually everywhere. The depth of these trenches will depend largely on the ground conditions at a specific site but will generally be more shallow than conventional foundations anyway and won't be "wet" like poured concrete.

The reclaimed railway sleepers are made from very high grade reinforced concrete with 4 steel eyes (2 on each end) that were used to fix the rail to the sleeper with sprung pegs. They are 25+ years old and have come to the end of their service life for railway use, but are still fine for decades to come for this application! There is a continual rolling replacement programme for railway sleepers so there should be a plentiful supply. Although the ones used for this project came from the Stoke-on-Trent depot, it is hoped that they could eventually be sourced from track replacement operations closer to home. They are free, with only the delivery to be paid for. CSBT ordered 100 since the transport cost was the same as for any lesser number.

Each house requires only 18 sleepers to form its footing, arranged in 6 rows of 3 laid end-to-end on 2 metre centres on the compacted hardcore. Any slight variation in the depth of the sleepers can be overcome by the adjusting mechanism on the steel brackets that will fit to the sleeper eyes. The design is somewhat unconventional in that the house isn't 'anchored' into the ground but merely sits on the hardcore. The weight of the sleepers and the concrete panels in the house will be enough to ensure that it doesn't blow away!

The sleepers, which had been already been pressure-washed to remove years of accumulated grime, were moved around the factory on a hand operated "pallet truck" to get them into rough position (well done pallet truck ace Harriet!), though this would be impractical on the rough ground of a building site. Since we are building this prototype on a concrete factory floor, this stage is somewhat different from what would be experienced in a 'real' build, though we discussed the potential problems that would be faced such as uneven ground and gradients etc.

The sleepers were then lifted into position by a rotating crew of 4 people using a looped nylon strap at each end, fed through one of the eyes and hooked into a "karabiner" (sprung-closed metal ring as used in rock climbing) with an iron bar fed through for someone at either side of the sleeper to lift. Even with 4 people working together, they are still VERY HEAVY! On a real site, it would be more practical to use a crane or even have them unloaded from the back of the delivery truck directly into position using the truck's crane jib. The positions of the sleepers are then fine tuned with the aid of a sledgehammer and block of wood.

We also learnt how to use an "optical level" for setting out a real plot with "profiles" - horizontal battens of wood fixed to two stakes driven into the ground at each corner and at the end of each row of sleepers - which will all be at the same level to give a reference for adjusting the height of the in-filled trenches, sleepers, support brackets and ultimately the ground floor of the house. This is done relative to a 'datum' - a fixed point on the ground somewhere on the site that won't move throughout the build. The optical level is somewhat like a theodolite but less complicated. You have to level the eye-piece itself over the datum using the built-in spirit level and then read the height on the staff being held by your assistant at the point you want to reference e.g. the height of the ground floor. You then move the staff to the place you want to install your profile (having already staked the ground) and adjust the height of the staff to achieve the same reading in the eye-piece of the optical level.

We then picked up all the sleepers and returned them from whence they came ready for tomorrow's crew to do the same!!

The first of the glued, laminated "glu-lam" timber sections will be arriving next week to begin building the floor which sits on custom-made adjustable supports which fix to the existing metal eyes on the sleepers - these are still being fabricated at this moment in time. Beyond that we are looking forward to some Amish-style "barn raising" of the timber frames that form the skeleton of the house... stay tuned.

I will endeavour to start taking pictures and/or video from next week to supplement the written diary and make a presentation at the end of the build.

Very tiring but very worth it.

Day 2: "The Glue Lambs"

If you've been waiting with bated breath for the next instalment of the ZED build diary, don't think that I've been tardy with last week's write-up... a delivery delay with the timber frame scuppered last week's progress, so we're now playing catch-up with most "builders" spending two days on the build this week.

The timber sections that we were awaiting were the "glu-lams" (glued, laminated sections) which have also been dubbed "glue lambs"! For this prototype these had to be ordered from Germany since no-one in the UK currently has the capacity to manufacture the sizes required. For the production models it is anticipated that a UK source can be found. All the timber used in the build has been specified to be from a FSC (Forestry Stewardship Council) approved sustainable source.

The glue lambs, er, glu-lams, are several smaller pieces of planed timber bonded together along their length (and sometimes end-to-end) to form a single section that is stronger (and cheaper) than a single timber of the same size. They look somewhat like wood strip flooring but in three dimensions.

Being a prototype the glu-lams were delivered uncut and so all the notches, rebates, joints and holes have to be cut, chiselled and drilled by hand. This is quite labour intensive but teaches us valuable carpentry skills which will need later inside for fitting floor joists, door framing etc. On the production houses, all the sections will be precisely, factory 'CNC' cut using a computer controlled jig. 

Rob and Lewis, our on-site carpenters, used a circular saw on each section to make the initial cuts of the correct depth. We then chiselled out the remaining unneeded parts to start forming the rebates in the horizontal beams that will sit on the sleepers and the tenon joints and notches on the upright posts to, respectively, fit into the beams and interlock with the horizontal beams that will form the second storey floor and roof line.

Just before "clocking off" time the first of the adjustable metal "shoes" arrived from the fabricator just down the road. This critical piece of engineering secures the timber frame to the railway sleepers and allows vertical adjustment to level the frame. The shoe sits on the sleeper and fixes to the two eyes that were used (with twisty spring clamps) to secure the rails to the sleepers in their previous lives. The eyes are almost flush with the top surface of the concrete which means that a bolt the same diameter as the eye cannot be used because the head of the bolt, and the corresponding nut, would not fit. A smaller bolt will be used with a metal sleeve (bush) inserted into the eye to reduce the diameter of the eye. This part of the shoe is only to prevent lateral movement and won't be taking the vertical load of the house so this is fine.

The vertical, heavy gauge bolt that supports the load bearing bracket is adjustable over several 10's of millimetres to allow levelling of the frame to allow for slight variations in the vertical positioning, and depth, of the sleepers. This levelling must be done BEFORE the frame is attached to the shoes since the adjustment bolts won't be accessible once the beams are in place.

Next time (tomorrow in my case!) we will be fixing the adjustable metal shoes to the sleepers, levelling them using the optical level and beginning to attach the glu-lams beams and then the vertical posts...

Day 3: "Out of the ground"

With all of the metal shoes having arrived from the fabricator just down the road, the day promised to produce some really tangible results!

The six rows of railway sleepers each have 3 of the metal shoes bolted to them. The outer ones have a single adjustable foot, with the inner ones having two - they carry a thicker post above them so they are designed to carry a greater load. The second row of sleepers from the south end has extra shoes. These will support the wall between the conservatory/atrium and the inside of the house proper.

I believe the intention was to level all of the shoes before attaching the beams but they are too unstable without the beams on them to accurately to this, so they will be levelled once the beams are in place.

The six rows of sleepers each carry two glu-lam beams, marked and cut in pairs, which sit either side of the shoes and bolt together through the shoes to form one member. Each pair have rebates (shallow cut-outs) about 10 mm deep which form a "mortice" when they are stood up on their narrow side - these had to be aligned with the metal brackets on the shoes. The upright posts of the timber frame have "tenons" cut into their ends which fit into the mortice and also sit on the shoe so this has to all be perfectly aligned!

Again, being a prototype, it was necessary to offer the beams up to the aligned shoes and mark the beams accurately to drill the holes. Having drilled one of each pair, the marks can be transferred to their twin.

The front and back (south and north) pairs were fitted first. We had to tweak the position of the sleepers to fit the beams to the shoes so we rechecked the orientation of the front and back rows relative to each other and re-adjusted them to get them back in alignment. We then used the optical level to set the levels of each of the four ends to be exactly the same. The shoes have a 46mm adjusting nut to raise or lower the bracket over several 10's of millimetres. There is a locknut below this to secure it in place, though this cannot be tightened with both beams in place which will have to be addressed in the design of the shoe for the production houses.

The side rails are cut to align with the rows of the glu-lam pairs and the notches will sit down on the ends of each pair. These don't seem to bear any (vertical) load but they ensure that the rows are properly spaced and square so that the rest of the frame will fit! This house won't be traditionally wonky like some old Cornish houses!

We were able to use the side rails as a guide to ensure that the rows were parallel, equally spaced and that the whole frame was square. We managed to get another 2 pairs of beams in place before "knocking off"

It is really satisfying to be "out of the ground" although we were never really "in the ground" in the first place! Progress should be rapid now. Next time we should be finishing getting the uprights in place and then the other horizontal beams between them at the first floor and roof levels.

Day 4: "To crane or not to crane?"

It has been 7 days since the last visit to the build. Since my last day the remaining two glu-lam pairs were fitted to the sleeper/metal shoe assemblies and everything squared up to the side rails which are now fixed to the beam pairs.

The floor joists that will carry the ground floor have been fitted, sitting at right angles to the floor beams in metal hangers nailed to the beams. Sheets of thick plywood ("ply") are lain on the joists (though not fixed yet) which will make it easier to work at that level.

We were told about the problems that previous days' builders have faced with fitting the floor joists - variation in the sizes of the timber and in the dimensions of the hangers: the single joist hangers are a different depth to the double joist hangers which are used where there will be extra load above them such as walls. The joists were fitted on 610mm 'centres' (the distance between the centre line of each) because this corresponds to the standard size of ply sheets: 1220mm x 2440m (or 4 feet x 8 feet in old money)

Our Health and Safety briefing identified the potential hazards that we would face today, since we now have overhead structures including very heavy timber beams etc. which we must be aware of at all times with constant vigilance. Also, we will now be in contact with ironmongery such as bolts, screws and the metal joist hangers all of which can have burrs, sharp edges, etc. so care must be exercised to avoid cuts. Employing the correct manual lifting method and appreciating the proper maintainance of hand tools - a blunted tool is more dangerous than a sharpened one - will also help to guarantee our safety.

It had been decided to fit metal plates on the joints of the glu-lam pairs forming the base to better cope with the weight of the frame. Since last week the frame of the northerly (back) wall has also been raised and is secured to the base with temporary braces which will be removed later.

Joe, the project manager/foreman, explained the problems that we would face with erecting the remaining frames. The already-in-place most northerly frame (number 1) is the least tall of the frames, but the rest would give problems because of their height and the available working height of the factory crane. Some creative solutions would be needed to manoeuvre these into position!

Each of the timbers used to assemble the frames requires at least 3 or 4 people to lift and move them, so imagine the weight of 7 or more of these beams and posts bolted together! The erection of the frame on-site will most probably require a crane, although it could be possible to fit each post into the base individually and then offer up the horizontal beams, though this would require many more pairs of hands! With the production kits having precision, CNC-cut (Computer Numerical Control) timbers this might be possible.

Number 2 had been pre-assembled behind ("north" of) the house and ready to lift into position. Assembly requires aligning the vertical posts with further pairs of glu-lam beams which would form the upstairs floor and the roof-line. The notches in the posts and beams fit together and need to be secured with two bolts passing through both the beams and the post altogether. Templates the same size as the notches had been made up to ensure that the holes were in the correct place every time. It is structurally critical to ensure that the two holes were 1/4 and 3/4 the way up/down the notch, and central left/right, to maximise the strength of the joint.

No. 2 was "stropped" through the upper glu-lam pair to help stabilise it during lifting and moving. Ropes looped onto the protruding ends of the beams allowed some degree of control to stop it swinging while moving it, and to steady it while lowering it into position in the base. The tension on the ropes can then be relaxed and they can be whipped off from the beams.

The frame was so tall that it couldn't be raised high enough to clear the upstanding on the side rails, so the frame had to be taken to the southerly end of the house, rotated, and moved backwards between the side rails.

   

After moving Number 2 we soon realised that Number 3 would not be able to be lifted with the upper beams attached because of the height restriction. This itself caused concerns about actually being able to lift the frame (shaped like two H's: HH) without it contorting wildly under it's own weight.

The "strops" from the crane's hook were attached on the outer edges of the inter-floor beams (and securely tied to the side posts to stop them slipping inwards) but this might have allowed the frame to topple since the posts were longer above the beams than below. Some temporary braces were screwed across the frame (below the height where the upstairs ceiling beams would be) with the strops fed underneath, but these couldn't take the stresses when the whole lot was put under strain with the crane and they threatened to snap if we continued so the frame was laid down again.

Chris hit upon the idea of using one of the as yet unused beams as a temporary counterweight and brace on the BOTTOM of the posts. Brilliant! It added the torsional rigidity that the frame needed and meant that the bottom was now heavier than the top! As we began to lift it with the crane again, with the strops above the lightweight braces, it was very stable and not top heavy! We also attached a rope to the top of the central post and fed that up and through the crane hook to act as a pulley to add some control over the frame while lifting and moving it. 

   

The tenons on the bottoms of the posts needed some adjustment to fit comfortably into the mortices in the floor beams, although they were cut accurately. This might be due to the timber swelling so it has been suggested that a metal sheathed foot to the beams may be the solution for the self-build kits to avoid having to "adjust" them.

The "central" post (although actually offset from the centre) on Number 4 projects about 1 metre (3 feet) above the roof for attaching the wind turbine (the electricity producing device, not the wind cowl for the heat recovery ventilation). There is no way this would have been able to stay there so it was carefully sawn off (and saved!) to be reattached later. We got Number 4 in place too before leaving for the day, so just one more to go - I don't think that the conservatory wall has such a heavyweight frame.

It is great to be nearly completing the frame now since it gives an idea of the size and layout of the house. Seeing the semi-curved roofline take shape is probably the single most defining feature. By next week the remaining frames should be in place with the permanent cross beams fitted at first floor level to give a safe, rigid structure such that the temporary braces can be removed. Then we will be fitting the ground floor ply. Then there should be a faster pace of progress with more "parallel" jobs rather than everyone having to collectively concentrate on one task.

Day 5: Floored!

The first job of Day 5 was to install the last remaining frame (number 6). Contrary to what I had thought, not all of the glu-lams had been delivered at the same time so the remaining frame had only just been assembled (and frames 3 and 4 are still missing the top beams). It was winched into position with the crane. With the posts in their final positions, a long boring drill was run through the pair of glu-lams and the tenon on the bottom of the post and a bolt fixed through all three to secure them.

  

The previous days' crews had installed frame 5 and fixed some of the plywood sheets on the ground floor and fitted most of the floor joists for the upstairs floor. With the last frame in place we could now carry on with the floors. We marked up more ply and continued on the southerly side of the ground floor.

Having fitted the floor joists on 610mm (2 foot) centres the sheets of ply only needed to be cut to length, not width. They were cut "long" and "short" to stagger the joints. Some needed to be trimmed to fit around the posts. Each 1220mm wide sheet needed a centre line ruled down it to show the centre of the joist underneath so that we could screw "blind" through from the top and reliably hit the joist! Using an "engineer's square" the centre of the joist was marked across the glu-lam beams and then transferred onto the side of the beam to be visible when the sheet was in place. A straight edge (an off-cut of ply) was used to rule the line, which was then marked off at around 300mm intervals for the screws.

  

Pilot holes were drilled at the marked intervals to ease the process of introducing the screws. The holes along the centre of each panel were drilled vertically, but the holes on the edges were drilled at an angle towards the centre of the joist since otherwise we would effectively be using half the width of the joist with more chance of screws protruding from the joists. It also gives a stronger fixing than using all vertical screws.

Battery operated screwdrivers made light work of fixing the 2-3 inch wood screws. We were told to be careful to ensure that the screw heads were flush with the ply (particularly the angled ones) since otherwise the protruding heads could damage the membrane which will be laid on top of the ply. On a 'real' build these would probably be nailed, but since this house is being taken apart again, screws are an easier option! 

Rob and Lewis, our carpenters, had to fit a temporary safety rail around the outside of the upper storey (for "Health and Safety") before we were allowed up there to work

While they were doing this some of us fitted the remaining upstairs floor joists between frames 5 and 6 which form the half-width terrace in the conservatory outside the master bedroom. The others chiselled the remaining glu-lams which will complete frames 3 and 4 (the tallest ones that hadn't had the top beams in place while moving because of their height)

    

By the end of the day we had most of the upstairs floored too. A crew with drills followed by a crew with screwdrivers got the sheets fixed down in a very short space of time. Where the stairwell will eventually be has been left unfloored which we are using as an access to the upstairs floor.

It is noticably darker "downstairs" now since the upstairs floor is blocking the light from the factory ceiling lights!

In one day we made a big difference - we now have a complete ground floor, and most of an upstairs too! Getting up there still requires some effort since there aren't any stairs yet!!

Day 6: Strutting and decking

Since last time the remaining glu-lam beams had been added to the top of frames 3 and 4 which were missing. They were winched into position using the crane with builders waiting on mini scaffold towers ready to fix them in place. Because of the need to use the towers, the parts of upstairs floor that are above what will become the stairwell (that we had intentionally NOT joisted) has temporarily been floored too, which was necessary to use the towers in the right place. It also makes moving around upstairs safer until the stairs are delivered and fitted.

To strengthen the frame some threaded metal bar has been used to cross-brace the wall sections at the front of the house where additional timber posts have been interleaved between the glu-lams to form the walls and door openings. The cross braces require angled rebates to be chiselled to take the nuts, which will then be concealed in the walls once they are finished.

In addition to the completed main frame, the metal "Uni-struts" have started to be added to the posts where there will be walls. The Uni-struts bolt to the centre of the posts, and the prefab concrete panels will sit between adjacent struts and brackets will clamp them in place, secured to the struts. Timber trim will then conceal the struts and the fixings. Uni-struts are not usually employed for this but are used for cable ducts and support cable trays and pipework in factories, offices etc. (There is some on the lighting gantries in the factory!)

    

Adding the same Uni-struts to the ceiling to accept the same panels is more difficult, and obviously more critical since the significant weight of the concrete must be borne wholly by the struts. The struts are first fixed to a wooden beam using bolts every metre, which is then fitted in the gap in the glu-lam beam pairs. Stout 12mm threaded bars are then fixed through the glu-lams and the new beam. A mis-calculation meant that we didn't have enough of the bolts required to fix the struts to the beams, which should be sent tomorrow. The longer spans of strut on the east side of the house require two struts end-to-end (a whole one and a part of another) so that requires extra bolts since they each need to be fitted securely.

The storage deck (attic) in the tallest two centre sections of the house had already had most of the joist hangers fitted to them so they just required joists to be fitted. The storage deck is constructed in the same way as both of the floors but the space above is only a few feet high, just enough to give some storage for the inevitable items that any household accumulates. This still needs to be decked with plywood sheets as before. The stud-work for the west wall has been started.

We also started assembling stud-work frames that will form the exterior north wall. These frames are like conventional timber framing construction: straight cut pieces of 100x50mm ("two-by-fours") timber simply screwed together with short, horizontal "noggins" on the taller pieces between the uprights to strengthen the frame. These separate, alphabetically indexed sections will fit together to complete the external wall and fit to the outside of the glu-lam frame.

    

As more and more of the pieces fit into place it is nice to see the features such as the storage deck and even doors and windows (or at least where they WILL be) coming to be. The expo day has been postponed, taking some of the pressure off to finish in three weeks, as the original schedule had allotted, due to the delays of glu-lams and some other parts not arriving as predicted!

Day 7: Firewall and noggins

Apologies for out-of-focus photos on Day 7... digital camera set to macro lens setting. Oops!

Since the last time there has been more threaded bar cross-bracing fitted and some bracing beams with metal ends have been fitted between frames 4 and 5 at the inter-floor level and above the upstairs ceiling level. Most of the remaining Uni-struts have been fitted upstairs and down, after the remaining bolts had arrived to fix them to the beams, and the external stud-work on the east wall (which will be made up as an end-of-terrace "gable" wall) has been started. The storage deck has been ply'ed just like the floors, with an access hatch.

Although most of the Uni-struts had been fitted on the posts and attached to beams for fitting between the glu-lam beam pairs, some still needed to be fitted to the posts on frame 5 - the southerly wall between the atrium and the house proper. An obstacle to this is the cross-bracing that has been fitted. Two approaches were employed to overcome this. One was to remove the cross-bracing, fit the Uni-strut and then re-fit the bracing bolts through the Uni-strut. The other was to cut a section from the side of the Uni-strut to pass over the bolt in-situ.

Last Friday there was an opportunity to be certified to use a "cherry picker" platform lift - a battery powered, rechargeable, self-propelled, mobile scissor lift. The certificate is valid for 5 years so those who qualified can use one elsewhere, should they want or need to! The cherry picker will be used by those who attended the training course for "high work" on the outside of the house.

The day was spent pretty much as two crews - one working on the stud-work to form the outside east wall and the other fitting lighter frames within the posts on the west side to take plasterboard. Apart from that, some gaffer tape was stuck down along the joins in the downstairs ply floor to help to seal the house.

This demo house is being built with the easterly wall as a gable (end-of-terrace) wall and the west wall as the "party" wall shared with the next house. As such the construction will be slightly different. The party wall will have a "firebreak" behind the concrete panels to slow the progress of a fire in any one house to adjoining house(s).

The firewall is built on a light timber frame fitted inside (between) the posts. On to this is fixed two layers of gypsum plasterboard, with the second layer overlapping the first so that there are no gaps straight through, since this is rated to be fireproof for 30 minutes. The frames are fixed such that the two layers of plasterboard come up flush with the surface of the glu-lam posts, so that the concrete panels fixed between the Uni-struts which are ON the posts will fit flush against them.

The standard sized plasterboard sections didn't quite give the correct width to fit whole sections, so the timber frame had to have extra timber to "pad out" the end and an extra piece of plasterboard cut to fit. The plasterboard is heavy - 3 sections is as much as I could carry comfortably, but as I write I am wondering if it would not have made more sense to use "wallboard" which is the same but in larger sheets. I wonder how the standard sizes would fit the sections and how much waste there would be? Some of the builders are dubious over the sustainability credentials of plasterboard since gypsum is a mined product.

The original plan was to make up separate external stud-work frames for the ground floor and first floor and roll and lap the membrane lengthways along the section from below, working upwards, as each floor section was fitted. It has now been decided that the membrane will be rolled vertically on the frame over the whole height of the house once it is finished and the joins sealed with a special double-sided self-adhesive tape.

Building the stud-work frames for the east wall was mostly a matter of fitting noggins and window openings for the master bedroom and dining room below. The windows on the side and north walls are smaller than usual to help avoid heat loss - having more southerly glazing is more efficient. Most of the tall upright posts were in place, but the verticals around the windows and the noggins bracing them together needed to be screwed in place. We used temporary braces to hold the noggins in place while they were screwed in place since, working vertically, we were also fighting gravity! Definitely harder work than doing it on the ground as we did for the north wall sections, which still have not been fitted into place because of the changed approach. They will be fitted once the east and west walls are completed.

The two half-length staircases (there is a landing and 180º turn half-way) have been made (on a CNC jig) and delivered, though these won't be installed until all the "high" work has been completed and the temporary floor section over the stairwell can be removed.

It is really starting to look like a house now with the walls going in, and sections starting to be hidden. It is easier to imagine how it will look once it is finished!

Day 8: Like Lego, only heavier!

We were greeted today by the sign of around a dozen pallets of around 250 concrete panels for the walls and ceilings, the last of which arrived first thing this morning. The timber frame for the exterior of the east wall has been finished off, and the west wall too, which has had the membrane fitted.

The pre-assembled timber frames for the north wall have been fitted to the main frame and the two layers of fireproofing plasterboard on the west (party) wall have been extended and completed upstairs, including cutting them to follow the roof-line.

With a light crew for the day of only 4 builders (plus Joe, Rob and Lewis as usual), we started by fitting the remaining rafters to the roof, and adding noggins in between. The rafters probably have the most complicated cuts of the build since they fit to the beams at varying angles.

We started fitting the concrete panels to the inside of the west wall using special sprung nuts and bolts. The panels aren't as "white" as many of us imagined they would be. At least when fitted in the house they seem quite a dull grey. Maybe they haven't been made in quite the same way as production ones would be (these have been made upcountry somewhere and brought down on two articulated trucks!) but most people are of the opinion that they will have to have some kind of rendering or painting unfortunately. They have a more rounded finish than I was expecting on the edges where the panel meets - I thought that they would be square to give a virtually invisible join.

The special rectangular nuts have serrated edges that interlock with a similar profile on the inside of the Unistruts and are supplied with small coil springs that fit behind them making it easier to fit: the nuts are pushed into the Unistrut and rotated 90º and the spring then holds the nut in place while the bolt is introduced. The tension on the bolt then firmly clamps the nut to the Unistrut, but the spring can stay there anyway!

The panels are thicker than expected I believe - at least they are thicker than the depth of the Unistruts, which doesn't pose much of a problem when bolting a panel either side of a Unistrut since they will be the same thickness, but at the end of a wall the disparity is difficult to overcome.

During the day the double-glazed windows and doors arrived from the local joinery company (two truck-loads). When the truck first reversed in through the factory doorway some of us were shocked since we thought that they were µPVC - they had been ordered painted white. A lot of the builders have said that they would prefer them to be natural wood colour - you can see the bare wood in a couple of places where the frames were clamped while being painted. I think that it is a real shame, but maybe they will look better when fitted. Some nervous moments while we were moving them since each double door unit, of which there are 6, costs around £1,000 and 14 of the larger windows at £600 each. A big sigh of relief when the whole lot, worth around £20,000, were safely unloaded from the truck!

We fitted membrane to the east wall. The rolls of airtight, but breathable, membrane were rolled from the base to the roofline, stapled in place and overlapped with the next length. When completed, they were made airtight using a double-sided, self-adhesive tape to stick adjacent sections together.

We also removed the temporary upstairs floor section over the stairwell, in readiness for the walls and half-landing to be built and the staircases to be fitted.

Over the next week the windows and doors will start to be fitted and the concrete panels will be fitted to the walls and ceilings - using the hydraulic platform to lift them into position. Beyond that we will have to fit the weatherboarding to the east wall, which will also be partly lime rendered.

A bit of a seminal day today since all the (major) materials that we need to finish the house are now "on site". Being surrounded by concrete panels, windows and doors, weatherboard panels and countless rolls of insulation is daunting to how much there is to do but at the same time encouraging since the end is in sight!

  

But since the end is now in sight, a few of the builders are now starting to realise that we will soon not be seeing, or working on, the house every week :-(

Day 9: Concrete juggle

What a difference a week makes! It was clear last week that we had reached a stage where each week, or even each day, would bring obviously noticeable advances in the build. With this in mind, I made a point of going to visit the site mid-way through the week to take a few photos to capture the incremental stages.

   

Day 8-and-a-half!
All of the windows on the east (gable) and north walls are now fitted, as are a few windows and one of the double doors on the outside of the atrium wall. The ready-assembled windows and doors are lifted into position and screwed in place from inside the house frame, through into the window frame. The others have been left out, for now, to ease access for moving the larger materials for finishing the inside of the house. The concrete panels have been fitted to the downstairs walls and part of the ceiling using the hydraulic lift. Some ply sheets have been fixed to the outside of the north and east walls.

As in a conventional timber frame, the ply sheets are a structural part of the house. Although a sheet of ply can be quite flexible (you could snap it by jumping on it propped at an angle) it is very strong to resist shearing forces. The sheets help prevent the frame from collapsing like a "house of cards"!

 

(Note: the rolls of rockwool insulation are not going to be used until this house is re-erected in it's permanent site, since it would be very difficult to save and transport and would therefore be wasted)

Back to Day 9 proper: Again we were working on a small crew - Thursdays are a very quiet day now - and we spent the whole day fitting the concrete panels to the upstairs walls and ceiling. This is hard work! The panels are just about carryable by two people but to manipulate them takes at least three and preferably four.

    

The wall panels needed three or four people and steps for the higher ones. The panels are lifted into position, dropping the bottom edge in place and then rotated upwards until they are vertical. The fixing brackets which had already been loosely attached to the Uni-struts were then rotated 90º and tightened to hold them securely in place.

Some of the panels needed small sections cut from them to fit around joists etc. This was entrusted to Rob as it required the use of a cutting disc on a grinding tool and had to be done outside because of the amount of dust it produced. Concrete dust is not healthy stuff to inhale!

The ceilings required the use of the hydraulic platform lift, powered by a cylinder of carbon dioxide, onto which each panel was lifted and then raised up to the ceiling and jostled into place. The "double" and "single" fixers were utilised to secure the panels to the Uni-struts.

The single ones were used temporarily to secure each panel on the Uni-strut that is shared between two rows of panels, since that allows us to get the neighbouring one in without having to prop up the first one. With the neighbour in place a double bracket is fitted and the singleton replaced with another double to give two brackets on each end of each panel.

We found some of the concrete panels to have burred edges that prevented them butting up next to each other, which needed to be rubbed off using a waste piece of panel from a cut one used like an emery stone, or pumicestone! The panels seem to be of an inconsistent thicknesses and some are bowed, perhaps due to over-zealous curing of the panels to get them to us on time, leading to warping and irregularities?

  

As it stands at the moment, the addition of the concrete is very much detracting from the appeal of the house in the minds of some of the builders. Maybe it is because the panels aren't as white as first imagined? Maybe it is because the panels have a much more obvious join than anticipated and inconsistently so? It has more than a hint of "prefab" in the post-war house-building sense - that it is somewhat inferior and undesirable - so not in a good way!

While building a house is never going to be easy, the physical effort required to move, manhandle and modify the materials, as is proving necessary, is quite demanding and needs to be examined carefully for a production kit for an essentially "lay" crew to erect. In a factory, with ready access to a 10-tonne crane on a frame around the house, it is relatively easy!

Day 10: House!

Once again, I called into the build mid-way through the week to keep apace with developments, though this time I actually stayed for a while and did some work as well as taking photos! The most significant advances were around 'the back' of the house...

Day 9-and-a-half:

The first obvious advance when walking into the factory is that since last time some more of the windows have been fitted in the atrium. Some noggin work at the top of the west wall has finished that wall and means that the membrane can now be stapled in place.

The weatherboarding has been screwed onto the back (north) and east walls - these are overlapping horizontal strips of pre-treated wood. These have been screwed in place, to make them easier to disassemble (like everything else on the build) though in a real build these would probably be nailed onto a light timber frame fitted to the outside of the membrane.

A first coat of lime render has been applied to the north-east corner of the house. A wire mesh is fixed to the plywood wall to give a "key" to which the render adheres, with a lead flashing at the base to allow rainwater to run off. Paving slabs have been employed to act to keep soil and moisture away from the timber since on a real build the ground level would be higher - the house would sit in a shallow recess.

On the plans and the architects' model the lime render extends to cover the whole width of the downstairs level on the north wall and the east wall and carries on up the east wall towards the wind cowl to form an inverted 'T'. Since the lime render cannot be re-used when the house is re-assembled in its permanent site it would be very wasteful to render the whole area.

The remaining rafters were fitted over the atrium in readiness for the roof to be decked out with ply - the roof itself is difficult to see from the factory floor but it helps to establish what the house feels like inside, particularly upstairs!

Some of the concrete panels had to be cut to accomodate the sloping roof line at the back of the house over one of the bedrooms and the bathroom. A Uni-strut was used on the angle to secure them.

Some more of the windows were fitted into the huge glazed southerly wall around the atrium, this time it was the east facing windows of the gable end. Light pieces of timber are fitted between "columns" of windows which are then screwed through into the window frames, taking care to keep clear of the (expensive) sealed double-glazed units! These joining pieces will be trimmed later.

Back to Day 10 proper:

The entire atrium is now glazed! To me this is one of the most appealing features of the house, so it's completion is a big milestone. The wind cowl that is the defining feature of BedZED, and no doubt will be of RuralZED, is here! I've never seen one in the flesh, although seen pictures of them at BedZED. The top of the cowl rotates automatically to face the larger hole away from the wind - the passing wind creates a pressure differential which draws the stale air up and out from the house, while feeding fresh cool air in through the smaller hole and through the heat exchanger to pick up most of the heat from the stale air, without the two air streams ever mixing. The cowl will be fitted to the roof since it is such an important part of the design though it will not be functional since the ducting and the heat exchanger will not be fitted. Since we are inside a factory there wouldn't be much opportunity to test it out!

After the rafters were finished earlier in the week, the roof is on! The sheets of ply have been added though I don't think that anything further will be done, since it will be hard to see anyway. Some of the sedum grass has arrived, as would be used on the roof, which I believe will be on show for the expo day.

Again, we worked mainly as two crews: Jo and Crystal used the genie lift to secure and trim the remaining flaps of membrane around the roofline while everyone else focussed on fitting the remainder of the concrete panels to the angled roofline of the north side of the bathroom and bedroom.

This was a tough job, requiring four people to safely lift the panels above head height, with a fifth to fit a wooden packer on the upper edge. It was a near impossible task to get the panels to fit into place with the angled section attached to the back wall, so a section of it was removed to allow the panels to be lifted up through it and then slid into position.

   

Later in the day, we began to build stud work downstairs which will form the interior wall between the hallway and the kitchen.

One week to go! This will be fitting the remaining stud work downstairs and upstairs and plasterboarding, fitting the concrete floor tiles, fitting the stairs and trimming.

Final Week

I have abandoned calling this entry by the "Day x" notation, since during this last week the house is a hive of activity with many people coming in more than one day or part day to make the house as complete as possible for the expo days this coming Saturday and Monday.

Although much work is being done it is harder to capture in the photos since the house is now so much more enclosed. All of the major engineering jobs are done; it is now a matter of "trimming" by throwing up the drywalls, fitting wood trim pieces, fitting window catches and cleaning up etc.

Tuesday:

   

Since I was last on site most of the stud-work for the interior walls has been erected and plasterboarding ("drywalling") is continuing apace. The timbers are screwed down into the ply and joists below and upwards through the Uni-struts into the beams above, and to each other. The plasterboard is being fixed with screws specifically designed for plasterboarding. The large sheets of wallboard have slightly bevelled edges which when fitted together form a channel for the application of a skim of filler to make a wall surface ready for decorating.

   

The stairs have been fitted, complete with mini-landing and 180º turn half-way up. I understand that it was not an easy task to encourage them to fit properly. The area under the stairs is the first to have had the concrete floor tiles laid.

The otherwise pre-assembled windows and doors need the catches and handles fitted to them. This was a fairly straightforward task of inserting the square section metal rod of the handle into the hole drilled in the window frame to locate it in the mechanism and securing with two screws, although we found that some of them were hard to fit since the holes were bunged up with stray saw dust either from the joinery or from our work!

Thursday:

Yesterday (Wednesday), we were visited by a plasterer who filled the gaps between sheets of plasterboard with a skim of filler. He returned today to rub the filler back flush to the plasterboard: this occupied another 2 builders for most of the day also since there was a lot to cover. Needless to say it was a very dusty house today (as can be seen in the photographs that required the flash!) Infra-red heat lamps were being used in a couple of rooms in an effort to dry the plaster in time for it to be rubbed down. Once dry enough the walls will be given a quick coat of white emulsion directly onto the plasterboard and filler.

  

An electrician was also evidently on site since the house now has twin-and-earth cable running everywhere! Only basic lighting and a few sockets have been fitted (in the plasterboard walls) to provide lighting for the exhibition day and provide power for table lamps and for the fairy lights for the Christmas tree which will proudly stand in the atrium - how seasonal! The cabling seems to have been fairly easy to install with the supplies to the ceiling centre room lights running in the Uni-struts. The double socket outlets have been fitted in the plasterboard walls only avoiding having to cut or drill the concrete panels. The cables have been brought out to the service duct in the kitchen where they will be connected to a fusebox and a supply (from the factory in this case)

A second coat of lime render has been applied on the north-east corner of the house. It has been finished in two different ways to demonstrate a choice that the prospective purchaser could make - either a rough stippled finish, or a smoother finish.

A few of us began the day by hacksawing off the protruding threaded bar on the front frame of the house itself (inside the atrium) to allow us to nicely trim it, although hurriedly, using some ply sheets fixed to battens on the glu-lam to close off the front side of the storage deck (attic) This was arduous work - but of course on a real build these would have been proper bolts of the correct length!

Most of the remaining concrete floor tiles (at least the whole, uncut ones) have been loose laid on top of sheets of insulation. Between the concrete tiles in the larger rooms, namely the lounge and dining room downstairs and the two front bedrooms upstairs, planed beech timber has been fitted between the exposed glu-lams which complements them nicely. Beech cover strips have been made by fixing small battens about an inch square to a similar piece of beech wood which are fixed along the joints in the walls and ceilings between adjacent rows of concrete panels - this gives the pleasant illusion of being part of the timber frame though only the vertical glu-lam posts are structural and the rest is purely cosmetic!

Where there is a join and hence a Uni-strut in a ceiling the cover strip was drilled to allow the lighting cables to drop through. The same could be applied for wall lights.

Lewis finished off the stairs by fitting the balustrade and spindles to the sides.

At the end of the day the ramp for easy access was being built since the house sits a couple of feet higher than normal ground level! We also needed to ready the site for the public to visit by erecting a security fence to keep people, especially children, away from other parts of the factory still occupied by heavy machinery that we are not involved with!

Tomorrow should be a matter of finishing off the wood trim to cover the exposed Uni-strut fixings and the corresponding floor "beams" and painting the walls and the "second fix" of the electrics, fitting the lampholders and testing and connecting the supply.

The forthcoming expo days will be an opportunity to find out what the construction industry, Local Authorities including planning officers and the general public think of the house and to relay our experiences of building it.

I hope to take some more pictures at the expo days on Saturday and Monday to complete the RuralZED diary.

Expo Day

On Friday the house was finished as much as possible, though some areas have been left to show the processes involved, such as the Uni-strut and the floor composition. The electrician has been back to fit the lampholders and install the fusebox in the kitchen.

  

Furnishings, wall hangings, plants and ornaments have been arriving that will later be moved into the house to "dress" it for the expo. The kitchen had some appliances and worktops hurriedly fitted and some fake cupboards just for show! Unfortunately there was no time to dress the bathrooms.

  

Friday evening's edition of "Westcountry Live" (the regional ITV news programme) featured footage of the build from earlier in the week and a live interview with Paul Bright of CSBT which was excellent publicity. There was also a full page feature in the Western Morning News newspaper.

We met Bill Dunster of the ZEDFactory who created RuralZED and BedZED before that, who briefed us on some of the questions we were likely to be asked regarding the price of the house and the inclusions and options. The contracts with local suppliers for the various components are being negotiated at present so this will be more "concrete" (excuse the pun) very soon.

The Expo Day itself on the Saturday was a phenomenal success! The opening ceremony, introduced by Paul Bright of CSBT, included speeches by Bill Dunster, Tim Williams of the Camborne-Pool-Redruth (CPR) Regeneration Company and Cllr. Bert Biscoe who cut the ribbon.

The factory was packed with exhibitors of renewable energy products such as photovoltaic "PV" solar panels, water-heating solar panels and household-sized wind turbines, and suppliers of sustainable building materials (including sponsors of the house). Manic Organic provided the catering which I can personally highly recommend for any location event, this being the second time I have sampled their wares!

There were hoards of people queuing up to tour the house, one estimate of the total number of visitors was put at 2,000. The people, from all age groups, ranged from those who seemed merely curious about the house to those that were very keen to build something similar and who were well informed about the need to reduce environmental impact by using energy more efficiently.

Some of the trainee builders were on hand to conduct the tours which allowed the public to get a real taste of what it would be like for them to tackle as (largely) a self-build. There were some really intelligent questions about, amongst others, the type of insulation, the use of double-glazing versus triple-glazing and the finishes employed in the house such as the concrete floor tiles which some people wanted to know if different colours or finishes could be used, or if stone could be used instead. The lime render interested a lot of people - some who liked it, some who would prefer an entirely wooden clad exterior instead of the part clad model shown (using local red cedar) but realised that ironically that might be harder to appease the planning departments!

One featured that I had underestimated of the house that I loved, and the tour groups loved too, was the balcony in the atrium leading from the master bedroom - a desirable feature in any house, let alone an affordable eco-home! It was found to be difficult to pull people away from it!

Oh, and the vast majority of my tour groups thought, as I expected, that the windows were µPVC until informed otherwise!

This diary website was available on a PC in the factory for people to see the various stages of the build which was of interest to those people who were interested in the method of construction as well as simply the finished product.

Letters of positive feedback have already started to be received from the general public and the public sector personnel who subsequently visited on the Monday so hopefully there will be ZED houses appearing near you soon!

It has been a thoroughly enjoyable experience erecting the ZED house which I wouldn't hesitate to recommend to anyone who is interested in building an eco-friendly house. New courses will be run in 2005, so contact CSBT now if you are interested. The places are sure to fill up quickly! As well as learning about the construction of this particular house we have all gained a valuable insight into sustainable construction methods and learned skills from carpentry to putting up plasterboard walls which we will no doubt find useful in future even if it is just for DIY!

I would like to thank Bill Dunster's practice for designing such a fantastic house, Paul Bright at CSBT for the opportunity to participate in the build, Joe Fenn and his sons Rob and Lewis of Optimal Construction for teaching us and putting up with a bunch of mostly amateurs for 10 weeks(!), my fellow trainees for making it such an enjoyable experience, and Ruth and Dave for the loan of the digital camera and the post-processing work to upload the images without which this diary wouldn't have been possible!

Matt