Sloping floors

[markyyyyyy]

Having just moved into my 2 up and 2 down terraced house with stairs going up the middle, the back of the house (to the left of me as i walk upstairs) slopes 2 inches over a 3.5m span. I have lifted up the carpet upstairs, and the slope goes from the middle of the house (stairs) to the back, and that is the direction the joists run.

I believe this is historical subsidence.

I want to start upstairs and level it all off.

I was going to sister 4x2 to the side of the joists. Would you start from the high spot on the landing and work your way to the back of the house in the direction of slope, ensuring the new sistered timber joists are level?

Any advice appreciated.

I know it's a lot of work but it's worth more than the sloping bugging me every day.

Thanks.

 

[Deleted member 174758]

First thing I'd do would be beg, borrow, steal or even hire a self-levelling laser so that I could find out where the highest point is and then work from that. If it isn't too bad in areas it may be possible to sheet over the floor with plywood and level up with an SLC rather than rip the floors up. Without accurately surveying the situation you won't know

 

[oldbutnotdead]

I know your pain.
Recently fixed a similar problem but used 22 x 150 roughsawn planks as the sisters. In a money no object world i'd have used ripped 25mm ply for the extra strength, but the boards aren't spanning anything & so far (2 years in) everything is good.
Lifting the floorboards without wrecking them will be your biggest challenge (assuming they're t & g).
Laser is v good shout for setting out. I used a cheapie from Screwfix but discovered (from reversing it) it was running high by about 1.2mm/metre. Which adds up across 6m.

EDIT My joists were running across the fall so set the far sister first then worked backwards, meant i could use line and straight edge for fixing the rest.