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Re: GSBN:Low Tech SB wall
I haven't seen your design for these tests, but are the walls loadbearing or
the straw infill only?
Assuming they're loadbearing, we've been using designs for top plate and
base plate connections very effectively for the last few years. By this I
mean that we have no doubts that the methods work, and neither do our
Building Control officers, who have never refused to pass our buildings.
We usually use a timber baseplate that also incorporates the floor joists to
save on timber (and not use concrete). Into this we fix coppiced hazel stubs
that stand above the plate by 12" (300mm). We drill a 2" (50mm)deep hole of
1" (25mm)diameter into the baseplate timbers, and whittle the end of each
hazel stub to get a really tight fit into the hole. This is easy to do
because hazel, being a natural material, has a wonderfully irregular
With the top plate, we again construct it of timber, and incorporate the
floor joists into it if it is to be a 2-storey building. Our top plates
always have a top skin of plywood for rigidity, and before fixing this ply,
we drill through specially placed cross pieces of timber and pin the plate
directly into the bales using hazel of length 39" (1m) and diameter 1 1/2 or
1 1/4" (38-30mm). Again, because of the natural bend and irregularity of the
hazel, it holds very tightly into the straw, much better than metal rebar
ever did. The ply top skin acts to prevent any possibility of water running
down the pins into the bales. Finally, we do tie our walls down, usually
with stranded galvinised metal rather than plastic, but only because we
can't find a plastic fastener that can be fastened and re-fastened easily.
These ties are not to stabilise the walls, as we consider that the weight of
the roof does that all on its own, they are simply to hold the roof on in
the event of a high wind.
We try never to use metal within our walls, we never wrap metal around them,
and we try to keep everything as simple and straightforward as possible.
If we are constructing an infill design of strawbale wall, we always make
sure we have compression on the infill panels, and have developed different
methods of doing this, but the top and base plate fixings would be the same
as described above. We would not use external pins any more in our designs
as they are very labour intensive and there are better ways of acheiving the
same result. We generally think that the use of pins is really an aide for
self-building, and that once the building is completed it probably makes no
difference at all to its stability whether it has pins in it or not.
I hope this is useful.
Amazon Nails: Strawbale building, training, consultancy, empowerment.
Warning! Strawbale building can seriously transform your life!
----- Original Message -----
From: tim Owen-Kennedy timok@...
To: GSBN GSBN@...
Sent: Monday, February 17, 2003 11:26 PM
Subject: GSBN:Low Tech SB wall
> hello all,
> We are winding down the testing portion of the EBNet's straw bale
> construction testing program and we will be building the cyclical in-plane
> test walls in Illinois over the next three weeks. Without going in to the
> details, we are testing 3 earth plastered walls and 3 cement/lime stuccoed
> walls (quickrete exterior stucco). Each of these sets range from
> simplest/most common to reasonably engineered to over engineered. ;-)
> The question that I would like input on is the top plate and base
> for the simplest earth plastered wall. In California we don't have much
> occasion to build with this commonly built wall. We really want to avoid
> folly of a silly solution that everyone will have to replicate. We will
> strap the wall with poly every two feet. This however does not seem to be
> So here is what we're considering:
> Mesh wraped under the sill and over the box beam that just covers the
> and top course of bales. ( most logical for us mesh happy balers though if
> you're gonna mesh top and bottom you might as well go all the way.
> unfortunately that is our mis range wall.
> 16d galvinized nails 4" on center imbedded only one inch into the plates
> box beam.
> Developing a decent way to hold onto the top and bottom plates with
> bamboo pins
> Imbalers, wood 2x2 top and rebar bottom (I really like to avoid this but
> has been done quite a bit)
> 16-18" Sip screws with wide washers installed after the first course and
> an angle up into the box beam (something I've tried with window bucks)
> Also, if someone will be near the Urbana, Illinois testing site and could
> help plaster let me know.