Self build offgrid strawbale house in Scotland

[Pord67]

Hello folks

 

My partner and I are three quarters through a self build strawbale house in rural Stirlingshire. We're fully offgrid with solar pv and rainwater harvesting.

 

There's a lot of carpentry involved and I've done most myself, including building a 6 x 4m workshop on site. 

 

I've already used Buildhub to find the answers to many questions, and am looking forward to posting my own. Happy to answer any questions on our build.

[DavidFrancis]

Well I'd be interested to hear more details on your build and see some pictures!

[joe90]

I considered a straw bale  build and helped on a couple of sites with theirs, looking forward to details. Timber frame?, spray or hand applied lime render? Etc etc. Oh and welcome.

[Mr Punter]

It sounds like an interesting project.  I would be very interested to hear about the pros and cons of straw bale construction.

[PeterW]

Sounds fascinating ..! I’ve got a few straw bale books but never had the chance to put it into practice ..!

[ProDave]

I wired one straw bale build many years ago,  but there are loads of different ways of building with straw bales.  Would be interesting to see how you did yours.

[Pord67]

Couple of pics as requested. Load-bearing strawbale walls, lime render inside and out (starting that this week).

[joe90]

Very nice, spray lime render or the hard way??? What did you use to strap the wall plate down, can’t quite make it out from the photo.

Edited July 1, 2020 by joe90

[Mr Punter]

I love it. Is the whole thing raised off the ground?

[Pord67]

We're going for it the hard way, rendering by hand, but keeping an open mind about reverting to spray if it proves too much.

 

Yes, the entire house sits off the ground on stacks of tyres rammed with pea shingle. No concrete anywhere in the build. No DPC needed either.

[Conor]

Love it, fair play to you, some amount of work in that.

 

No roof lights? One or two small ones would bring in loads of light and not a huge cost.

[joe90]

  On 01/07/2020 at 17:11, joe90 said:

What did you use to strap the wall plate down, can’t quite make it out from the photo.

Expand  

@Pord67 ???

[the_r_sole]

This looks sweet, open for visits when the lockdown eases? Be really interested to pick your brains a bit on how you got it through building warrant/SER etc!

[Pord67]

Sorry Joe90, forgot to reply. The pic below from early in the build might help illustrate. There are two box ring beams, one at floor level (sitting on the rammed tyres) and the other sitting on top of the bale walls. The trusses sit on the top one. At each doorway and window there are posts that connect the two ring beams. In addition, there are webbing straps (the kind used on pallets) looped around both beams. You can see them in the interior pic. 

 

And yes, visitors will be very welcome when it's finished! 

[joe90]

Ah, so it’s not really load bearing as the roof load is on the timber uprights.? (Only interested as once I had extensive plans to build a straw bale house but chickened our ?) I helped lime render (plaster) a straw bale build and those straps, if not tight to the bales, made plastering difficult (they “twanged” the lime back at you). My design had steel cables and turnbuckles above the wall plate so you could wind down the top plate (no timber uprights).

 

i like you’re idea of getting the roof on prior to inserting straw and wrapping In poly to keep the weather out. With mine (two story load bearing) i planned a complete scaffold house outside, with temp roof, to enable building inside a waterproof structure then remove scaffold.

Edited July 4, 2020 by joe90

[Onoff]

Love it...but what stops the "infilled" walls compressing over time and creating a gap at the top?

 

Did you have to wire it in MICC/FP?

[Triassic]

  On 04/07/2020 at 09:21, Onoff said:

Love it...but what stops the "infilled" walls compressing over time and creating a gap at the top?

 

Did you have to wire it in MICC/FP?

Expand  

Looks like plastic conduit from the ceiling.

[ProDave]

  On 04/07/2020 at 08:57, Pord67 said:

Sorry Joe90, forgot to reply. The pic below from early in the build might help illustrate. There are two box ring beams, one at floor level (sitting on the rammed tyres) and the other sitting on top of the bale walls. The trusses sit on the top one. At each doorway and window there are posts that connect the two ring beams. In addition, there are webbing straps (the kind used on pallets) looped around both beams. You can see them in the interior pic. 

 

And yes, visitors will be very welcome when it's finished! 

Expand  

Ah so the bales are not actually supporting the roof load.

 

The one and only straw bale house I wired had 2 timber frames, one inside and one outside with the bales in between. So the bales were literally just insulation piled up in between.  the exterior cladding (timber) was fixed to the outer frame and the interior service void and plasterboard was attached to the inner frame.

 

If yours is being lime plastered inside directly on the bales, I would love to see what you are doing with wiring?  All in conduit I assume, but how do you fix a socket back box to a straw bale?

[Onoff]

  On 04/07/2020 at 09:23, Triassic said:

Looks like plastic conduit from the ceiling.

Expand  

 

Can't really see on this phone. Thought it might be white FP...

[Pord67]

Blimey, hope I answer everyone!

 

No, although the posts do contribute a little the primary load bearing is done by the bales. In theory if the building had no doors or windows the roof would be sitting on nothing but bales. It's absolutely not an infill design. By the way, the roof is temporarily held a little higher while the bales are inserted, then the roof is physically dropped on to the top of the bale walls. That was flippin scary...

 

The wiring is in metal conduit, which is then sandwiched in scrim and rendered over. We also have some internal stud partitions that can take wiring and plumbing.

 

For sockets, we hammer in a hazel stake around 250mm long and screw a little square pad of Smartply on to that. Socket boxes then screw to that.

[Strawman]

Thanks so much for all the sharing. Build has started on mine so this level of detail is incredibly useful. Hope the weather stays dry while the rendering happens. Where did you source all the plastic to cover it till the rendering starts?

 

Mine is a barn and will be a hybrid method of partly load bearing, sitting on gabion baskets. Off grid but trying to look to the future with every feature so copied all the words on how you have managed getting leccy in. I'll be 12V, batteries and jennie for the forseeable though. 

 

[joe90]

@Strawman looking forward to hearing about your progress.

[Pord67]

Sounds interesting Strawman. I've got details coming out my ears, so just ask away.

 

The covering is scaffolding sheeting and has been absolutely invaluable, so much easier than heavy tarps. It comes in rolls of assorted widths, is lightweight but strong, and is fully waterproof. Very easy to attach to appropriate points and we use a combination of staples, cable ties and nailed or screwed strips of timber. The best part is its transparency, meaning the interior is not in darkness.

 

We too are totally offgrid, currently with 1kw solar pv and battery bank. I prefer to use an inverter so we can use conventional appliances. Just last week we added an under counter freezer to our facilities.  I also use a wee inverter genny to run the workshop.

[Crofter]

Really interesting project. How did you get on with Building Control with this construction method?

[NSS]

Fascinating read and I have huge admiration for anyone choosing to build and live off grid. Not sure I could cope without all the creature comforts afforded by electricity on demand.