Timber floor joists instead of I-Joists -advice required

[evo111]

I am in the process of having a first floor extension built above my double garage. The architect and structural engineers plans include the use of I-Joists spanning 4.8 metres spaced every 400mm. (The area being floored is 4.8 x 9 metres).

My builder however is not keen on using I-Joists because of the additional expense to me and the hassle in ordering them. He wants to use traditional wooden joists.

I am happy to go with what he decides but my question is :-

Can traditional joists span a length of 4.8 metres adequately - they will be hung at each end on joist hangers with no supporting walls between ends. I dont want to put them in only for the building inspector to complain !! I also do not want 'bouncy' floors when the build is complete !!

Advice greatly appreciated.

 

[JohnD]

...The architect and structural engineers plans ...

so ask the architect if he agrees to the proposed change. If he does, ask if he will clear it with BCO. I expect he will charge for amending the plans.

If you make an unapproved change you have no warranty or BCO approval any more

 

[jeds]

I expect your builder is finding the thought of 'I' beams a bit scary. They are quite new after all - they've only been around for about 20 years.

Standard timber joists can span 4.8m OK but to achieve a fairly stable floor with little bounce you would need to go to something like 75x195mm or possibly even 220mm - which won't be cheap.

 

[noseall]

225 x 50mm joists at 400c/c with third span bracing may work, but as jeds has said - pricey.

At least with pre-fab 'I' beams you have a hollow substructure so no need for sparks or plumbers to drill and there is no need for additional sound suppressing insulation.

 

[freddiemercurystwin]

They are quite new after all - they've only been around for about 20 years.