Minimising floor depth / yet another span tables question

[garyo]

When you have a house with 100mm tall first floor joists, and this house is being extended, is it common/known to use 100mm RSJ's to break the new spans up so that 100mm tall joists can still be used in the new extension? i.e. where the householder doesn't want a step down in the ceiling?

Thanks

Gary

 

[noseall]

The only houses i have ever seen with 4" deep joists are old cottages with large timber beams at mid-span.

If this is the case then i suppose it would be ok to replicate this using modern methods either with a mid-span steel or a timber alternative.

However, i would be reluctant to try and replicate such a 'fussy' arrangement when deeper joists and a thoughtfully crafted step would be simpler and more sensible.

 

[garyo]

Indeed, my lounge has two of the large timber beams that you speak of. The remainder of the wall layouts downstairs have been designed such that the spans are never large enough to warrant them.

I could get away with 170mm tall joists in the extension, so I'd only need a 70mm step down, and I'm considering the other obvious option which is to batten out a slightly lower false ceiling. That'd still leave 100mm of the wooden beams visible, which I don't think would look too strange, but comes down to sensitive design/though, as you say. Mmm.

Thanks as always!