[Strawbale] SB Arches

[Chris Mowatt]

Has anyone got experience of building arches in a SB wall? What technique
works best? Can SB arches be made genuinely load-bearing or do they need to
be re-inforced in some way? What type of SB arch is strongest and or easiest
to build. Roman arches seem simpler. Norman arches built of masonry are
structurally stronger and lighter than Roman Arches. Is the same true for
SB? How is a Norman arch achieved? How do you calculate the correct radius
for the curves in Norman arches and where do you position the centres?

We are planning four largish(2m/7ft wide) arched windows or openings in our
proposed four storey tower house castle. The floor structure of the floor
above will spread the weight of the upper storeys, but the section that
contains the arches will need to do its share of the load-bearing. Would it
be prudent to have a squared floor to floor timber frame and add arched SB
infill simply for aesthetics? Or can a SB arch be relied upon to take the
load and distribute it into the neighbouring wall in the same way a masonry
arch would? The arches could be deeper than the standard wall if necessary.
This would add strength and make for an interesting internal feature, but
we'd rather not if we don't have to. Likewise, we'd rather not have any more
timber-framing than we have to. We are trying to take the load-bearing
concept as far as we can.

Chris
Isle of Arran
Scotland

P.S.
I can already hear you sceptics out there sucking in your breath and saying
"He's gotta be joking! Not only is he crazy enough to build a four storey SB
building, but he's going to put damn great holes in it!". Well you guys have
got a shock in store.