Leveling upstairs timber floor

[SALL2009]

I’ll try to keep it simple.

I had a masonry none load bearing partition wall on timber floor of the second floor. There is no wall underneath this wall downstairs. So the weight of this wall on the second floor joists had caused the two joists underneath to sag a bit and the main back wall of the property developed a crack. All the above is determined by a structural engineer.

The structural engineer suggested that the partition wall is knocked down and to rebuild a partition stud wall. This wall was dividing a bedroom and bathroom. Due to the sagging joists the bathroom floor is lower towards the wall. The SE also suggested that I get 2 new joists installed, to level the floor as it is slanting.

Now I have knocked the wall down and ready to build the new wall.

I was wondering, is there any other way to level this floor instead of installing new joists.

I was thinking of attaching some plywood on effected side of the bathroom and then installing full sheets of plywood on the whole bathroom to level the floor. Does my idea seem ok?

Can someone give more suggestions?

 

[SALL2009]

Any ideas?

 

[RonnyRaygun]

You could bolt a new joist to the existing ones ensuring that you have it level, and screw your new Ply to that.

Have you got the same problem in the bedroom?

 

[SALL2009]

The bedroom is fine. Both problematic joists are in the bathroom. Thing is I want to find a way to level the floor without needing new joists, because old joists have been notched to get the plumbing pipes through. So it would be a lot of hassle to place new joists in place.

 

[RonnyRaygun]

OK. how about taking a new joist and cutting it into sections, so there's no new joist where the pipes are. Then bolt or coach screw it to the existing joist, ensuring it's level.

Or firrings screwed to the top of the joists prior to installing ply

 

[SALL2009]

Thanks.

firrings idea sounds good. I might look into it.

Also how about screwing a 2 x 4 to the current joists. The reason I'm reluctant to attach a new joist is that it was the weight that caused the original joists to sag. Wouldn't attaching the weight of another joist would make it sag more?

And would couch screws be able to hold the two timbers together? How many couch screw should be used per foot of the additional timber?

 

[RonnyRaygun]

The reason your joists sagged was because they were carrying the weight of around 2.4m of brickwork. This would weigh in the region of 600 kg / metre.

You'll be sticking a stud wall back on top which will weigh around 100 kg / metre, so you've reduced your loading by around 85%...which is good...

A joist on the side will weigh about 2.5 kg /metre...which isn't going to make a lot of difference

The timber on the side will only be carrying the load of the ply and finishes, and any imposed loads (and only 1/2 the load between it and the next joist), so again, not very much.

I'd put in 5x80mm screws top and bottom at 500mm centres. You should leave 20mm or so from the top and bottom of the timber to your screw centres. Coach screws might be easier as you can use a socket or spanner on them if it's a bit tight to get a screwdriver in there.
Also pre-drill your holes through the timber you're fixing.

The only problem I can see with firrings is that the deflected shape of your joist will be curved, whilst the firrings will have straight edges. Might not be enough of a difference to worry about though.

 

[SALL2009]

I was thinking of making my own firrings by temorarily fixign a 2 x 2 (where it is level) on the side of the old joist. Then drwaing a line at old joist level, then get this 2 x 2 cut and attach to the top of the joist.