New Look

We are now moving from building mode into marketing mode, hence a new look for the blog – in effect turning it more into a static website and moving the blog posts to one side where they can remain as a reference for people interested in straw bale building. Posts from now on are more likely to be about the garden, the local barn owl and other wildlife than straw.

We are also having an open day this coming Sunday. Anyone who can make it is welcome.

Invite

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Today was the day…

…that the photographer from English Country Cottages came. I therefore think it is as good a day as any to say “it’s finished”. These are not the pictures he took, they will be up on the ECC website in a few days, but ones I took to take advantage of the fact that we had ‘styled’ the house.

There is still some work to be done on the landscaping – mostly seeding some grass – but this will need to wait until the weather improves.

Once the English Country Cottages page is up-and-running I will change this website so that it focused on promoting the house as a holiday let, and less about the build – although all the build information will remain in a separate section or category.

Also – we are going to have an open day on Sunday 18th March, from 2pm until 5pm. Anyone who is interested is welcome to come round. Coffee, cake and maybe even something stronger will be on offer.

Ready for sign-off by building control

I guess that having the place ready for final sign-off by Building Control is a reasonable definition of finished. The last couple of weeks have involved doing the final big, messy outside jobs – primarily digging a 70m trench to bury the power cable and water and then laying down a paved area and path which was necessary to comply with building regs. for disabled access. I had hoped that I would be able to get away with compacted gravel, but according to the inspector any area had to pass the supermarket trolley test – i.e. allow a trolley to glide across the surface.

We also need to book an air test – which will be a good indication of how well I have built the place.

Following a pre sign-off inspection from Building Control, I have had to do a fiddly retrofit job on the windows in the bedrooms, because they didn’t pass muster for sufficient escape access. This was my fault for not checking closely enough with my own building regs. application but it raises an issue worth bearing in mind for any straw bale build. This is that if you are having a window that is a bale length in width (i.e. about a metre) and if you want to have a window that has a central post (mullion) which I think looks better than just a large single casement, the gap that you have either side of that mullion won’t be the requisite 450mm, because even if the window gap starts out at 1000mm you won’t have half of that available either side of a central mullion once you have deducted the width of the mullion itself plus the overall frame. The only option is to have what is called a floating mullion – where that mullion isn’t fixed solid into the window frame but is attached to one of the casements and will swing outwards if required. The people at Wooden Windows were very helpful in supplying me with floating mullion casement, but cutting out the old mullion, removing the glazed unit and fitting the new casement was quite a tricky job. I would have been far easier to fit a ready made floating mullion unit in the first place.

We have also had a visit from English Country Cottages, who will be marketing it as a holiday let, and fixed 23 March as D Day for letting availability. So this is the first ‘real’ deadline.

Last messy job

DSC_2178I am now tackling the last big, messy, inside job – sanding down and coating the floors. I have a deadline of the end of this week because that is when furniture is arriving from Ikea. I debated about staining the floor boards to try and give them more of an aged and weathered feel, but decided to preserve the ‘integrity’ of the material by keeping it natural, even if it does look a bit clean and Scandinavian.

Sign of the times

DSC_0126I am not sure you ever get to a point where you say ‘it’s finished’. The last two months or so have been filled with finishing-off tasks: fitting or making doors and door frames, installing the kitchen, painting, installing lighting – nothing of particular interest from a straw building perspective but hugely time consuming non-the-less. I have estimated that the man hours dedicated to the windows (installing, painting, glazing) have probably equaled the time spent actually raising the walls.

In terms of passing on advice, I would say to not underestimate the amount of time required to do all this stuff.

However, today a sort of milestone was passed because it was the day I moved the tools out and put them back in the workshop. Up until this point I have had an OSB sheet set on trestles covered in tools, screws and bits and pieces as well as random bits of wood and board distributed about the place – so it very clearly looks like a work in progress rather than a nearly finished project. But now, while there are still a few things lying around, it looks closer to a space which is waiting for furniture (and also sanding the floor, which is the last big job that remains to be done). I feel I can now say that the project is almost finished – just some snagging jobs and, of course, the sanding and finishing of the floor.  It will be done by Christmas.

 

Clay plastering a straw bale house

This is a post I have been meaning to write for a while: a review of the experience of clay plastering. The first point to make is that I don’t think I arrived at the absolute definitive method, finding myself constantly experimenting with different mixes and application techniques in order to find the optimum balance of the various considerations involved: these being adhesion, cracking, gap filling and time.

The considerations

Adhesion

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Adhesion coat

It was much harder to get clay to stick to straw than the Limecote I used on the outside which could be sprayed-on and built-out to possibly even 40mm in a single application. Using clay, it is necessary to put-on an adhesion coat. This should be mostly pure clay, to make it sticky possibly with a little sand added to give it a bit more strength. This layer can’t be too thick, because a clay rich mix, while sticky, will crack a lot and also will not be strong enough to allow it to be built-out. It s also worth noting that clay is more expensive than sand, so you don’t want to use more than is necessary. The issues with this adhesion coat are how sloppy to make it, how thick to apply it and how to apply it. My solution was to make a pretty sloppy mix (consistency of double cream) and apply it with a gun to a thickness where the straw was coated and stray sticky-out bits could be encouraged to lie flat but not to the point where the coat starts to build-out.

I did find that I got some areas where, after applying subsequent build coats, the clay was not strongly bonded to the straw and therefore was inclined to crack, but this mostly occurred where there was weakness with the underlying straw surface, either because the straw was rather soft and wispy or because there was a gap which wasn’t adequately packed-out. Where these were an issue I hacked off the clay and started again, making sure the clay was very well worked into the surface.

Gap filling

I probably wasn’t as diligent as I should have been on gap filling. This was partly because the Limecote was so good at bridging across gaps or soft areas and also because of the time required to do a thorough job packing out gaps with a straw mix. I therefore tended to rely on my first build coat to fill-in any gaps but this could lead to cracking and weakness if I didn’t sufficiently force this coat into the gaps. For this reason it would probably be best to spend some time really packing-out any gaps with a long straw dubbing mix.

Cracking

Cracking can happen for two reasons: either your mix doesn’t have enough sand and/or fibre added to it, or if the clay is insufficiently bonded to the straw underneath – because the straw surface is wispy and unstable or there is a gap beneath the clay that isn’t well packed-out.

I think I got the fibre issue cracked (as it were) by using concrete screeding fibre. This is much easier than using chopped straw because you don’t have to chop it. I did use chopped straw initially and found the best way of prepping this was to put a load into a dustbin and then plunge the strimmer into it, preferably with someone holding the dustbin lid over the top to prevent too much flying out. The only issue with fibre, especially screeding fibre, is that if you use a sponge to finish-off your top coat, this will drag bits of the fibre out, resulting in a hairy finish – but this can be dealt with by using a blow torch to burn these off.

As mentioned earlier, I got some minimal cracking of my first build coat, but this was mostly over gaps. I dealt with this by tapping the cracks with a hammer, and if the area around the gap sounded hollow, I would knock the gap out and ram clay (or sometimes dubbing straw) into it. If the gap seemed ‘natural’ and reasonably firm either side I just left it and filled it out with the second (and final) coat.

I didn’t get any cracking of my final coat – which I figured must have meant that the mix was right and the fibre was doing its job.

I did initially experiment using a fibreglass mesh which I stuck on top of my first build coat. This did stop any cracking but I was deterred from using it extensively because the supplier of it said it should be sandwiched into the final coat which effectively meant making the final coat two coats (as in two bits of bread if the mesh is the butter in the middle) and this was too time consuming. That said using it as a layer between the first and second coat didn’t seem to create any problems, such as creating a weakness or potential for ‘shearing’ between the two coats – although I guess only time will tell if this might develop as a problem.

Time

I underestimated the length of time it took to do the clay plastering, possibly because the experience of the external rendering was easier than expected (Limecote being such a magical material to work with) or perhaps because the internal walls meant there was a considerably greater area to deal with. Using the gun didn’t seem to speed things up, other than when using it to spray the adhesion coat. When I used the gun for the first build coat, I found that I could go faster by hand, especially if I kept this layer relatively thin and when it came to the final layer pushing it on with a trowel was also faster than standing there with the gun waiting for it to build-up to a sufficiently thick layer. This was probably because I was using a basic gun and compressor. If I had more powerful kit I probably could have sprayed thick coats on quite quickly.

Because of the length of time things were taking I also tended to miss-out the gap filling stage, as mentioned above. This was probably not ideal, but I don’t think it has caused any long-term problems (i.e. clay dropping off at some point in the future), but I guess only time will tell on this one.

Recommended process

If time (or labour) wasn’t an issue the absolute best process would probably be the following.

1 Adhesion coat

Apply a slip coat of 3 to 1 clay to  (plastering) sand with a gun, mixed to a consistency of double cream. Apply this to a thickness such that the straw is well coated, but not starting to fill-out.

2 Gap filling

Make up a batch of long straw dubbing mix. This is straw with a clay / sand slurry poured into it. You could make this slurry by taking the slip coat and adding some sand to it to firm it up a little. This mix should have the characteristics of straw bound together with clay, rather than clay with straw added to it. Use this to pack out any gaps or soft areas, ramming it in as firmly as possible. Unlike the lime (a chalk fibre lime such as Limecote), clay is not very good at bridging across gaps and soft areas and even if it appears that you have covered a soft areas well, the likelihood is that it will be weak and crack easily as it dries. You could (probably should) do this while the slip coat is still wet. This should get you to the point where the surface is relatively flat and firm, but still basically strawy.

First build coat

Make up a batch of clay that is 3:1 sand to clay with fibre added. I used concrete screening fibre (a couple of handfuls per 60kg batch – ie one 15kg bag of clay powder plus 45kg of sand). I mixed this in a regular cement mixer, tumbling the dry mix first and then adding sufficient water to take it beyond the golf ball clumps stage, past the big lumps stage to the point where it starts to slump. Something like the consistency of cream cheese. Then apply this by hand, really ‘grinding’ the mix into the straw, using the heel of your palm, having first dampened down the straw with either a mister on a hose or by using a pump-action sprayer. This layer need not be that thick, but you should get to the point where the wall no longer looks strawy, but more clay like, with odd bits of straw poking out.

Let this coat dry out so that any cracks can fully develop. Then test the cracks by tapping them with a hammer to see if they sound hollow around then. Those that are hollow, knock-out and fill with a clay mix or possibly by ramming a long straw mix into the gap. Alternatively you could wait until you start to see cracks develop as the coat dries and then push the still damp clay into the straw along the crack line with your finger tips.

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First build coat on right, second/final coat on left

Second build / final coat

Get the wall good and wet with a mister. It is amazing how much water the dry clay wall will suck-up. I tended to give it a good soak, to the point where water is just about to run-off the surface, and then wait five minutes or so and give it another go. Apply a 3:1 sand to clay mix with fibre using a trowel to a sufficient thickness to give a decent covering to any straw poking out. I find descriptions of coats by thickness rather unhelpful with straw, since its irregularity will mean that a coat which in one place may just cover the straw, will in others be 30mm thick. I used the trowel to get the surface reasonably flat and smooth, but tried not to work it too much, and then used a wet sponge trowel to further smooth over the surface. This produced what I guess you would call a rustic finish, which I was happy with. If you wanted a better finish you would probably need to do a third skim coat which you could spend any length of time working-up to whatever finish you want, rubbing it with a wooden float or a stone or whatever. The great thing about clay is that it doesn’t set, it simply dries-out so you can rework or revisit the surface as much as you like.

Finally, once this coat is dry, get a blow torch and ‘wash’ the surface with flame to burn-off any bits of fibre or straw.

A (psychological) door

DSC_0008We have just fitted the door. This was actually a very simple task (using the same company as supplied the windows), however it represented an important psychological milestone. Whilst your door is a sheet of OSB you don’t really have a house, you have a building site. It also means that we have a proper air-seal so it makes sense to light-up the pellet boiler – an important step forward given the sudden plunge into autumn.

Rain skirt

One of the many finishing-off jobs is putting on a rain skirt at the base of the building. This has two functions: to protect the base plate and throw any rain that runs down the building away from the foundations and also to protect the car tyres from direct sunlight, which can cause them to degrade.

Before rendering I had screwed a 2×2 timber through the woodfibre and into the timber of the base plate. This acted initially as a render stop, although the sticky nature of the Limecote mean this wasn’t really necessary. What I have now done is screw a piece of standard black stained weatherboad at an angle into this timber and nailed onto this a piece of 90 degree angled plastic beading. This beading can act as a new render stop for a a strip of render that overlaps the top of the weatherboard (see pictures).

I am pleased with the result. It finishes-off the base of the wall and gives the the whole house a slighty suspended feel.

Elsewhere, I have been finishing off the flooring and been back on the tyres and gravel again, but this time for the less critical job of providing a foundation for decking. I will use the scaffold boards so that the same material that is the interior flooring also then runs-out as ‘exterior flooring’ albeit with a small gap between the planks to allow rain to run-off as well as having set the decking on joists that are on a 1% angle to further encourage run-off.

 

 

 

More flooring

DSC_0696I am now putting in the finished flooring on top of the chipboard sheets that sit on top of the joists. I have decided to go for scaffold planks. The problem with most conventional flooring products is that they all look too perfect (as well as being pretty expensive if you want solid wood as distinct from a laminate). For a project such as ours you need to have a floor that looks suitably rustic – and scaffold boards do just that.

Scaffolding Direct sells new, unbanded boards in various lengths, which work out at a cost at around £14 per square metre. This will give you a chunky 38mm, 23cm wide, board. The boards will obviously need to be sanded and finished, but the look is so much more solid and attractive. Interestingly, the price of new boards is about the same as recycled ones and since both would need to be sanded and the used ones are more likely to be damaged, as well as having bands on the end that would need to be removed, buying new seemed a better option.

I am nailing them down, rather than screwing them, because I think boards like this need to have visible nails to look suitably authentic. I would like to have used cut nails, but this won’t grip into the chipboard, so I am using good old ringshank nails. I got boards in lengths of 2.4m so as to get a good number of joins, since I think this also is a better look. I expect to get a little shrinkage over time, but this shouldn’t be a problem because big boards like this look better (more authentic if I may say that again) with slight gaps between them.

 

Window detailing

It has been a long time since the last post – mostly because we have been doing ‘non-straw’ jobs, such as installing bathrooms and kitchens and painting which are not especially interesting or noteworthy tasks. I have been meaning to write a review post covering my conclusions from clay plastering, but haven’t got round to it yet. However, last week I got back onto a straw specific job, namely finishing off the exterior render around the windows.

I had left the window area without a finish coat because I needed to get the windows themselves in before doing this and I wasn’t able to do that job before the winter lime rendering window closed. As luck would have it I received a surprise visit from Arthur Phillip, the lime render man, who happened to be in the area. Arthur is probably the country’s foremost expert on rendering straw bale houses and he introduced me to PVC window frameseal beads. These are basically a strip of white PVC channel with a sticky back to it that you can put around the wooden frame edge of the windows allowing you to render up to and into the channel – thus giving you a stable and watertight edge to your render. They also have on the a tear-off sticky plastic strip which you can use to attach polythene sheeting to in order to protect the windows themselves from render spalshed – important if you would be using a gun to apply the render.

I couldn’t actually source these in sufficiently small quantities, so I made my own by buying standard PVC channeling and runing a bead of silicone up the back of them to stick these to the frame while also creating a weathertight seal. I then mixed up a batch of lime and straw to create the shaping into the window frame and finished-off with a coat of lime that then ran into / up to the window edge fo the PVC channel. This seems to work fine.