Roof joists

Get a structural engineer to yea or nea the structure?

- Grade of wood has a bearing, C24 can be thinner than C16 for example so dimensions are only 1 parameter. Same goes for spacing and so on.

Check if BR changed over the period from original application?

- BR at time of original application apply, if that has any bearing (I doubt it, but you never know since they may be based on assuming the worst rather than what a structural engineer says you can actually get away with).

Joist sizing will be calculated from span, weight of roof covering, estimated wind loading etc.

I'm assuming this has been done on a building notice, rather than a full plans submission? If full plans have been passed by building control, and you build to plan, you're home and dry.

First thing is to get somebody to go through the calculations and see if any value can be tweaked to get back within regs (e.g. the roof covering may be lighter than the value specified, plasterboard ceiling changed etc.).

If you have to physically change something, beefing up some joists with side-plates is probably the least hassle solution.

Yes. Building control will go 'by the book' unless someone with more authority says 'OK' In this case its a structural engineer.

An if the timbers are accessible like roof rafters, its very simple to fix. You can double up every third one or something and add purlins.

Bolting metal strips or even plywood to the sides will probably do it easily. However you will need an engineer to produce a design so the building inspector will pass it.

All useful info thanks guys. One suggestion from a 'bar room' expert suggests flat steel fish plates, is this feasable/reasonable?

Thanks

How ridiculous. 7mm, what's that, 3/16"? They won't sign it off because the joists are undersized by 3/16". I'm off for a lie down.

Good luck Richard

surely much cheaper to stick a bit more wood up.

NT