What are the rules for tapering/chamfering floor joists (ie where they're being tucked under the eaves on a wallplate in a loft conversion)?? The old approved document on structure suggests a minimum bearing of 35mm for joists (at full width/joist thickness). But I wonder how much you could cut down the thickness (height) of the joist over this bearing area? Presumably there's some sort of shear calculation for this - can anybody point me in the right direction?
your structural engineer is the man for this as a single joist can not be taken in isolataion it will vary depending on the spacing of the joists, the expected loads they will be carrying the angle of the roof etc the floor must be taken as a whole
You are correct in your assumption that there is a shear calculation for this. Get a structural engineer involved. If you have done a loft conversion, the few quid he charges will hardly scratch the surface of your budget. I could tell you exactly what to do, but having spent years at university and 20 odd years in practice, I make my living selling my expertise, not giving it away for free. Its not that myself or my peers are mercenary, its just that there could be so many other factors involved that it is pure folly to give this sort of advice out without looking at the job in situ. The more probable outcome is that you will cut it away and if it does not collapse then it is safe.