Adding straw bale to heighten existing stone building.

Hi all

has anyone increased the height of their build by adding straw bale on to and existing (1,5metre) stone wall to take the final height to around 3,5 metres?

IMHO that’s a lot of extra height (2 metre )  to take up with straw ( but I’m no expert at building with straw bales). You would definitely need to build a support frame for the roof etc. When I built my cabin I added an extra 12 inches by using 9”x12” sill plates I cut.  I’m curious what you’re using your building for that you want that tall of walls?

@B Steinmetz
Thanks for your reply.
So its an old pig pen which will serve as a small studio for friends and family when staying over.

Yes the roof is the obvious part to make sure its stable. Were very exposed on top of a mountain with strong seasonal winds.
I was thinking of not resting the roof on the bales but putting in 6 wooden posts and fixing the roof to these with a frame, then building up top the roof with the straw bales.
Do you think 3,5 metres is too high?
How high is your roof?
How will you secure the roof to the stone walls?

Cheers
Sebastian

Having built with strawbales before, it is important that your existing walls are squared off, so you can add bricks or concrete/limecrete to make the walls horizontal.

From there, you can add a wood frame (any wood in contact with existing wall should be treated!) and make sure no moisture can run up to the bales. Because they will spoil if they get damp.

Seeing you want high ceilings (which is nice), you can first work on a wood frame and then in-fill with bales.

Many times, strawbale houses have a 40cm brick wall, on which they put the bales, to keep the bales away from moisture.

Sebastian Wolff wrote:@B Steinmetz
Thanks for your reply.
So its an old pig pen which will serve as a small studio for friends and family when staying over.

Yes the roof is the obvious part to make sure its stable. Were very exposed on top of a mountain with strong seasonal winds.
I was thinking of not resting the roof on the bales but putting in 6 wooden posts and fixing the roof to these with a frame, then building up top the roof with the straw bales.
Do you think 3,5 metres is too high?
How high is your roof?
How will you secure the roof to the stone walls?

Cheers
Sebastian

It sounds like you have a good plan, an Erik Slagter has some excellent sounding suggestions.  To answer your questions: I don’t think 3.5 metres is too high, especially if you go with a flat roof. I ( personally) like shorter walls with a vaulted ceiling, but that’s just individual preference. My walls to the top of the sills are about 2.1 metres and the peak of the ceiling is about 3.3 metres.  Due to the mass of the sill plates and the roof structure it simply sits on the stone wall, and it has never moved, even with some mild earthquakes, though it’s not technically a dwelling, so I didn’t have to meet any codes etc.  This is the finished cabin....

I would like to see some images of what you have before I comment.
I have experience.
What you want is feasible, but there are a few things that need to be done, depending apon what is already in place.

Wow your pad is beautiful. Thanks for the info. Ill look into the wooden roof frame indeed.

B Steinmetz wrote:This is the finished cabin....

Well, that's just ridiculously awesome.

Sorry to be joining the conversation late.  Sebastian, I'm with John on this one--do you have a picture or drawing of what you have there, or what you propose to do?  If the stone wall--thinking of it as a stem wall in this situation--is as wide as the bales you plan to use, the challenge will be the connection (with sill plates) to the stone wall, and how that all relates to framing (if any) that supports the roof.   If the stone wall isn't as wide as the bales you want to use, you probably need to build out the stone wall--thicken it--so it's at least as wide as the bales.  I can imagine several ways to do that--all have trade-offs.  And whether you thicken the wall to the interior or exterior has trade-offs, too, related to the structural load paths and if you want to add insulation to this part of the wall.

Bale walls are usually finished with plasters on the exterior and interior surfaces, although it has become more common to also use siding (over exterior plaster base coats)--several ways to do this.  It may also work to use exterior plywood sheathing for shear, stack the bales to the inside of this, and install some sort of siding over the plywood.  Note that the plaster itself weights around 15 lbs. per square foot per inch of thickness, which is probably too much to cantilever over an unsupported straw bale edge.

Jim
Many Hands Builders
S. Oregon

Hi Jim

Thanks for your message.
Ill arrange some pictures.
The wall is 55cm thick. I think our local bales on their side are more or less that.
I like Steinmetz´idea of building the wooden frame, screwing (or something similar) it to the stone wall then filling in with straw bales.
I also recently did a cob workshop and that might be an idea as well.

Ill arrange some photos.
Regards
Sebastian