Uneven floor joists, how too level b4 reboarding

[tvrjohn]

Hi
carrying out a loft conversion in a 200 year old farmhouse

Joists are very uneven 20mm or so and not straught either

Don't fancy packing them level, can i use some sort of expanding foam on top of joists and lay then nail/srew boards when dry ?

any suggestion please

 

[Softus]

carrying out a loft conversion in a 200 year old farmhouse
.
.
.
any suggestion please

At the risk of appearing uncharitable, I get the feeling you haven't done this before, and that you don't have enough experience to tackle it.

For example, do you need LABC approval, and, if so, have you obtained it?

 

[tvrjohn]

Have submitted application for Building Control

my first post, and i'm not getting much constructive feedback

 

[OLD]

Are the existing timbers strong enough to support a floor there usually only sufficient for occasional access

 

[Softus]

i'm not getting much constructive feedback

You get out what you put in, so when your description of the entire technical, planning and building control considerations comprises the sentence "Joists are very uneven 20mm or so and not straught (sic.) either", then what do you expect?

If you want my opinion, the use of expanding foam should be limited to repairing damaged areas in lumps of expanding foam, not in any kind of serious construction work, although I have to conceded that it's extremely handy as a gap filler around window and door frames.

You've already cited packing as a means of solving your problem, but you said that you don't fancy it. Why?

 

[anobium]

Totally agree with Softus.
At the very least you could tell us the size of the joists and the length.
If they do not conform to basic requirments for loading it is pointless trying to level them.
More info please

 

[tvrjohn]

More info, thats fine
joists are 80mm x 80mm oak on a 350 pitch, very hard and span is 3 metres as rooms below have a mid positioned support beam of approx 200 x 200 section.

 

[Softus]

It sounds as though you could build another house on those joists then!

But why are you so against packing the joists to get the flooring level?

Maybe someone else will, but I can't think of any other way to overcome the problem and still maintain the strength. The other alternative is to floor the area in narrow boarding and let the character of the building shine through.

 

[kevnurse]

I think I understand why you don't want to pack the joists. The uneven nature on the top of them means that every pack height will be different and the aim of a level floor will be very difficult to achieve with most of the packing located away from the edges of the new floor panels. Also, a hollow sound will result when the floor is walked on.

IMHO the best option is to sister the joists across the area to be floored with timber deep enough to level out the humps and hollows and have sufficient overlap (3"?) with the existing joists to fit the connecting bolts. I would use 2" wide sisters to give room for the floor T&G and fixings.