Thanks Ben ! Yeah ahaha ... there was quite a time when I couldn't sleep thinking about whether they would work or not,
I have made all the cob by hand (starting with a backhoe but then forming each ball buy hand adding straw when necessary), I didn't embed any extra reinforcement ... I spoke to an engineer once about adding timber and he said the straw is reinforcement enough (I don't think he understood the material properly). I did however do a tension test on my cob mix a few years ago and it was quite promising (I embedded two welded prongs in some cob and then hung the cob block vertically and added weights to try to separate ... I ran out of weight ! ahah pics below) , so I believe so long as the cob is mixed well and then laid intelligently (so you have long thicker strips that 'tie' it back into the structure we should be alright
Yeah the arches will be built up to about 300mm at the crown, I can hang my weight of each crown though at the moment (70kg so I am pretty happy with that already),
I think the buttresses would be a good idea ! I would not be at all comfortable with someone else building these eave supports (and I don't think I would do it readily again in the future), I was very careful with how built them and the cob I used (and I have tested their strength the whole way along).
I think the timber is a good idea (I was going to have to embed some into the top of the arches and eaves so I have something to nail the timber I will span the arches with).
Good point about failure (I plan to do many safety tests once the roof is on, adding extra weight), but It would be good to have a bit of a warning if anything was to happen.
I would like to go on after this project and scientifically collect some data on how cob performs under different loading
Any idea Ben on how far out eaves on a cob house should go ? (I was also thinking if I do put the timber on top of the arch if it was strong enough I could extend it out slightly further past the end of the cob eaves to get me a bit of extra distance)
Thankyou very much !