Off grid Strawbale House in Devon.

[Delbot]

Hi all,

We have got planning for an offgrid 2/3bed strawbale house in Mid-Devon which we are aiming to be near passive house standard.

If anyone wants to look at the plans the application number on the Mid Devon portal is 20/01631/FULL.

We are aiming to be cement free so my present dilema is the foundations. 

I have worked on car tyre foundations before and they were very labour intensive, also not sure on the lifespan of the tyres.

we have looked at building on gabions filled with stone but these have a suggested lifespan of 60 years.

We have thought about using trenches full of clean compacted 40mm stone  with the ring beam for the bales sitting on top but the structural engineers want us build a block wall on top of the stone.

I would be keen to here other peoples thoughts especially if anyone has experience with cement free foundations.

Thanks, Del

[Conor]

Limecrete? See it used a fair bit here.

[SteamyTea]

12 minutes ago, Conor said:

Limecrete

Little, if any, environmental benefit over OPC, and at least cement set hard.

 

Going to be an interesting challenge to get a non cast foundation system past the building inspector.

Edited March 27, 2022 by SteamyTea

[MikeSharp01]

Helical piles and a frame built on them? Have look here: https://gbgs.co.uk/our-services/

 

Edited March 27, 2022 by MikeSharp01
Added link

[SteamyTea]

14 minutes ago, MikeSharp01 said:

Helical piles and a frame built on them?

Yes, that is an idea.

I am assuming that @Delbot wants to go low embodied carbon and energy, and recycle.

Our old mate Ed Davies dug some holes, filled them with stone, then a small cast concrete cap, if I remember right.

It will be here somewhere:

https://edavies.me.uk/blog/tag/perihelion/index1.html

[MikeSharp01]

14 minutes ago, SteamyTea said:

, and recycle

That could be achieved, somewhat, by @Delbot finding the equivalent weight of piles in scrap iron and recycle it to keep it circular?

[SteamyTea]

6 minutes ago, MikeSharp01 said:

finding the equivalent weight of piles in scrap iron and recycle it to keep it circular

Tarmac is the worlds largest recycled product, followed by concrete.

Cement is not that bad in reality.

Edited March 27, 2022 by SteamyTea

[Cpd]

I guess your going to be constrained by the SE but what about filling the trench with stone as you have suggested and then trying to acquire some large cut stones to lay dry on top of this instead of blocks, when I built a road in Australia I used over one ton sandstone blocks purchased from a local quarry, they worked out very cheap for what they were and will be there is a few thousand years. Tightly fitted they will go nowhere and if absolutely necessary you can join them in the middle with stainless steel rod, the stones I laid were just put down on a crushed stone bed and laid without mortar between the joints (there is mortar in the middle of the track but it’s not structural to the outer stones, just there to “look” like loose crushed sandstone) these stones were aprox  1200mm  long x 600mm wide x 250mm  deep. The road was full designed by a structural engineer to closely resemble my design. 

[JohnMo]

42 minutes ago, MikeSharp01 said:

That could be achieved, somewhat, by @Delbot finding the equivalent weight of piles in scrap iron and recycle it to keep it circular?

But doesn't most 'new steel' have a very large percentage of recycled materials in it already?

[MikeSharp01]

10 minutes ago, JohnMo said:

But doesn't most 'new steel' have a very large percentage of recycled materials in it already?

Yes but you could compensate for that as well. We need to get to a circular economy if we can everywhere we can.

[ToughButterCup]

1 hour ago, MikeSharp01 said:

Helical piles and a frame built on them?

 

I researched helical piles  : they would have been perfect for us , but the ground conditions for them are quite specific. Can't recall what those conditions were, but glacial till isn't suitable. 

 

I suspect ground-improvement columns aren't for you? (Compacted 'piles' (columns) of stone - bit like a pile? ) We built on 64 of them

Just in case, Town and Country Vibro did ours : our contact is John Ashton

 

 

[PeterW]

12 hours ago, Delbot said:

We are aiming to be cement free so my present dilema is the foundations. 

So if you’re doing this for low embodied energy reasons then don’t bother as your glazing will be more energy intensive - go with a concrete ring beam on helical piles which is a standard detail and then crack on with everything else. 
 

12 hours ago, Delbot said:

strawbale house ….  aiming to be near passive house standard….

What is your air tightness detailing as you’ll be into some pretty substantial air permeability with bales. 

[ProDave]

5 minutes ago, PeterW said:

So if you’re doing this for low embodied energy reasons then don’t bother as your glazing will be more energy intensive - go with a concrete ring beam on helical piles which is a standard detail and then crack on with everything else. 
 

What is your air tightness detailing as you’ll be into some pretty substantial air permeability with bales. 

The only that I have seen (and wired) put the rectangular bales inside a timber frame.  Think of a wide Larsen truss frame built around the bales as they were stacked.  Then the inside was lined with OSB and an air tight membrane then a service void and plasterboard, so air tightness was good.

[PeterW]

13 minutes ago, ProDave said:

inside was lined with OSB and an air tight membrane

Yep - which is basically using straw bales as a very expensive insulation .. would be better with blown cellulose at that point. 

[ProDave]

1 hour ago, PeterW said:

Yep - which is basically using straw bales as a very expensive insulation .. would be better with blown cellulose at that point. 

It was the tree huger, local materials grown in the surrounding fields, sustainable etc rhetoric that drove this one. 

[Iceverge]

Hi @Delbot and congratulations on getting planned permission. 

 

Can you expand on your motivations for avoiding concrete please. Is it the carbon or just that you don't like it? 

 

Both are completely valid, it's your house and your money. I would have loved to build a house raised on timber piles but very quickly I realised I didn't have the time, or the money, or the will to fight "the man" to the extent needed.

 

I quite like your drawings, it's a charming and unusual design.

 

Passive house is really very mundane in concept. Its just a school level physics calculation based on a sealed and insulated house.

 

It really specifies nothing about embodied energy in the material use so best to keep the two seperate.

 

You could build one from the highest GWP spray foams and steel and concrete and still get a very comfortable and healthy house to live in. 

 

Conversely an "eco house" with terrible air sealing, inadequate ventilation, badly installed insulation and a zero concrete approach might be easy on the world to build but very environmentally and financially taxing to run and uncomfortable to live in. That includes using lots of wood to heat it by the way. 

 

The best of both worlds is available of course. 

 

 

 

 

[joe90]

I started this journey wanting to build using straw bales, helped out on a couple. 

[Conor]

My friends had designed a straw bale house (bales as structure, lime render either side) and were going to use dry stone trench foundations. Unfortunately project fell through and never happened.

 

I'm assuming as you are avoiding cement you're mindful of the embodied carbon of the build? Have you down a whole life carbon assessment of the build or is this a ideological decision? You'd be surprised how little impact a small amount of the right concrete in the founds will make in the overall carbon impact of a build. A couple courses of 7n concrete blocks would be nothing over the life span of the building.

We looked at using low carbon concrete in our build, but wasn't feasible as it would have to have been mixed on site which wasn't an option for the grade and type of concrete needed. 

Edited March 27, 2022 by Conor