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RE: GSBN:Re: Strawbale walling query
Hello Tom (and all)
This is my first response, so please excuse any errors in protocol!
We built our SB house almost exactly as described, and the details we employed were as follows;
We fixed a strip of Fermcell (plaster board) to the back of the internal post that extended an inch or so either side, to allow a continuous plaster/vapour check with the internal render - you will get shrinkage of large section posts, and if we hadn't done this there would be an eighth inch air gap each side of the post.
We then fixed a fencing staple to the back of the post and used it to hold the bales in place with poly packaging strapping (the sort that comes with a tensioning device - very handy in a lot of SB building scenarios)
This was done not so much for structural reasons, as to help keep the walls straight and true but retain flexibility.
Without seeing the details, I am confused as to why there is a wall plate to tie to the rafters - in our post and beam, the wall plate is the top of the frame, the rafters sit on that, and the SB wall extends up between the rafters.
We have been monitoring our house with about 30 moisture sensors for about two years, and I would advocate a rainscreen. We are in a similar gulf stream climate, and the walls that are just lime rendered hold on average 3% more moisture than the screened ones (av. 13% against 16%)
I would also agree that the SB wall should wrap around the outside of the posts, not between - far simpler to build, and better continuous insulation.
PhD Research Student
Room 119, Reynolds Building
University of Plymouth
From: GSBN [GSBN@...] On Behalf Of Tom Woolley [email@example.com]
Sent: 04 October 2007 18:06
Subject: GSBN:Re: Strawbale walling query
I had a meeting today with a young Belfast architect, Siobhan Brown,
who is designing a strawbale house for a self builder in County
Fermanagh ~Northern Ireland
I don't think Siobhan has much experience of SB but she has had a
good go at the design mainly based on details in a book by Chris Magwood
The client wants to built a post and beam structure for the house and
then wrap the strawbale walls around the outside of the posts.
She was not proposing to tie the walls into the posts as she says
that Magwood's details do not show this.
She was planing to tie the wall plate to the rafters of the roof. The
house is single storey but with rooms in the loft. so the floor
joists for the upper floor will be part of the roof structure.
I have misgivings about this . I wonder if anyone has built a
strawbale house where the bale walls are not load bearing and are
wrapped around the outside of the structural posts without being tied
into them? The posts will be about 4 metres apart.
Fermanagh has to have 100% humidity all year round with a lot of
heavy winds and driving rain. If you stand still for 5 minutes moss
will grow on your head. I also think the walls will need a rain screen
I would have thought a more solid structure would involve placing
sections of bale walls between the posts and being tied into them
Any useful comments and I will pass them onto Siobhan
Rachel Bevan Architects
17A Main Street
028 97 512851
Graduate School of the Environment
Centre for Alternative Technology
Unit 7, Dyfi Eco Parc
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