Straw bale construction

[Asher Hoskins]

Hello.

Does anyone have any experience with straw bale construction? I'm pondering options for a self-build at the moment and a wooden framed house with bale infill looks interesting (mainly due to low U-value, speed/simplicity of use and cost).

Has anyone here built a straw bale construction? (Or even better, worked out how to fit one into the building regs!) There's a great deal of enthusiastic information online from straw bale advocates but some more dispassionate opinions would be nice.

Asher.

[BigWallop]

The only thing that really worries me on these types of buildings, is how do you make them fire proof? I don't mean from electrical or chip-pan fires, I mean from water droplets hanging around when the sun shines, or from lightning strikes etc.

How much does it cost to make all that straw fire resistant? Or does it come pre-prepared and treated, and with discount quantities?

[John Rumm]

Daub is probably the answer... IIRC there was a Grand Designs self build that used that technique. Once up the interior was daubed / plastered and ended up looking much like any other wall. Can't remember what they had outside. As the OP said good insulation and very cheap (handy if you set out the house design in multiples of bale length though!)

[Asher Hoskins]

While loose straw will burn easily, when bales are used in construction they get compressed and all the loose straw is trimmed off the outside before rendering. Prepared like this there's not enough air inside the bales to sustain combustion (the canonical example from the straw bale sites is to think about how hard it is to ignite a phone book compared to a single sheet of paper). Rendered straw bale walls are apparently more fire resistant than conventional building materials.

That said, site security from the time that the bales are first delivered to the the first coat of render is something that needs consideration (as does keeping an eye on where people fling their cigarette butts during that time).

Asher.

[BigWallop]

Ah ha!!! I wasn't with that bit. The Bales are actually used as the building blocks, then are fully enclosed in a plaster rendering. That makes sense now. :-)

I was imagining a load of straw bales stacked against the side of timber framed houses there, but it actually sounds like a great idea if the straw is all concealed behind a thick layer of plaster.

And the security and fire safety arrangements during construction would have to be a bit strict as well, wouldn't they. Must do a bit more research on this.

[BigWallop]

WOW!!! It all actually looks like a bloody good idea. After having a look for "Strawbale Construction" on the web, I now see what you mean about the energy efficiency and low cost maintenance on such a build. I'm off to have more rummaging around on this.

I wish you much luck if you decide to go ahead with it.

[s--p--o--n--i--x]

The other thing that worried me was damp.

If the straw gets damp (For whatever reason be it condensation or a leak in the render) it will quickly go mouldy. Spores/dust could then cause breathing problems.

sponix

[s--p--o--n--i--x]

Is that why thatched roofs never catch fire? After all, the straw is packed so tightly that rain can't get in..

sponix

[Baz]

Hi Asher. The woodman's house on Grand Designs looked like this :-

was a super house.

Baz

[Mike Halmarack]

I saw this method used on one of the Louis Theroux, whacky character shows. It was built in a remote, sparsely populated part of North America. I remember wondering at the time how long it would take for the straw bales to disintegrate, given expected humidity levels and sound construction methods.

There's a lot of vested interest in the high energy production of the standard insulation materials in this country and elsewhere. I'm sure they'd use their combined clout to see off this low cost, low energy interloper in very short order. Probably by use of the building regs.

-- Regards, Mike Halmarack

Drop the EGG to email me.

[Anna Kettle]

Lime plaster of course :)

I'd love to build a strawbale house too. A lime plastering friend of mine who lives in North Wales has worked on several strawbale houses via Barbara Jones (who is the Queen of strawbale in the UK)

Buildings with a structural timber framework and straw infill are easier to get planning permission for cos the calcs are easier to do but I prefer buildings where the straw bales are loadbearing

Anna

~~ Anna Kettle, Suffolk, England |""""| ~ Lime plaster repairs / ^^ \ // Freehand modelling in lime: overmantels, pargeting etc |____|

01359 230642

[Mary Fisher]

or

Hsy is NOT straw.

Mary

[John Stumbles]

The Centre for Alternative Technology

have built 1 or 2 on their site and doubtless have some book[let]s and other info on them.

[Mike]

I'm sure I read somewhere that the BBA was testing straw bales as used in this purpose. Why not ask them if they did and if so what the results were. If it passed this would have all the info you need for the building regs.

[Tim Lamb]

Hmm. What about vermin? The Grand Design program failed to even ask the question.

Straw bales contain a fair amount of unharvested grain and are predator safe winter housing for rats and mice. In order to get at the food they soon learn to chew through the polypropylene (sp?) string.

The on-farm cure is to bury a bag of bait sachets in the bottom layer but I don't know how effective or how much of a problem this might be for a single bale wall. Also farm stacks are used and rebuilt each year.

regards

[The Natural Philosopher]

They are not packed tightly at all. And the straws are like little flues, all pointing the same way.

[The Natural Philosopher]

I recovered thatch from UNDER the roof of my old house,whose then (not thatched) roof was at least 60 years old, that was in perfect condition.

Straw will last as long as wood if subjected to the same sort of damp free regime.

The key is as with wood, to keep it dry.

In quantity its a pretty tough material. Its also remarkably bullet resistant. I'd rather be behind two foot of straw than 1/4" of steel with someone pumping high velocity bullets around.

[The Natural Philosopher]

My feelings exactly.

Are you sure the loadbearing calcs for straw are not available?

Building in straw should be lioke building in blockwork.

And I should think expanding foam to hold door and window frames in woould be appropiate.

Not sure how to arrange for a wterproof skin though - breathable membrane, air gap, metal lathe and render maybe?

[The Natural Philosopher]

Its not hard to encase the straw in somthing tough enough.

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