How do you asses whether a species of tree is good to use or not?
For you Americans you probably don't have to because all your woods have already been assessed as to what is good and what is not for a particular job.
The reason I ask is because there are a number of trees in my area that are generally excepted to be good for fire wood and not much else.
Two cases in point are Peppermint (actually two species but they are similar) and mana gum. They have rather high tangential and radial shrinkage (P 6%r,11%t, Mana 6%r,12%t) and hence are a night mare to mill without significant degrade but could they be used in timber framing?
I was thinking that anything with a tenon might be a bad idea unless the members were quite small but posts might be all right? Or purlins or common rafters that are just pegged to principal rafters? Or battens that are pegged to common rafters?
Or what about pegs themselves? If they were kept inside so that they were extra dry then they would swell after they had been hammered into the frame? Would you have to be careful in that they could swell too much and split the wood they passed through?
Other than shrinkage rates what other information would you look for to asses a species suitability for a particular framing member. Details that I have already are density, modulous of rupture, modulus of elasticity and maximum crushing stregnth.
From those properties can you determine figures for vertical shear, horizontal shear, Fb and such?
