How to level the floor in a room with sloping Victorian floorboards

[Harry_W]

We are looking to board out and carpet a small bedroom but need to make the floor level as the existing floorboards are sloping quite significantly. What's the best way of doing this?

 

[TicTac]

Lift the floorboards, and sister new joist alongside the exiting ones. What's the height difference.

 

[KenGMac]

Are there any large gaps between the floor boards and the skirting boards?

Could be an indication of wood rot in the joist ends embedded in the external wall?

 

[Harry_W]

Thanks for the replies. I think the movement is due to a structural wall between the rooms below being removed or Nazi bombs during WW2. As the floorboards run under one of the walls it will be too big a job to lift floorboards and add sister joists. I'm thinking of just getting lengths of 2 x 2 cut to make the decline and then reboarding with quarter inch plywood.

 

[Deleted member 174758]

6mm plywood is OK if you are levelling up slightly uneven floor boards and will take-out differences of 2 to 4mm between boards before laying carpets, but nothing more. If the floor slopes then you'll either need to lift and sister as a previous poster recommended or add tapers to the top and overboard with something capable of taking the weight of humans, furniture, etc such as 18mm hardwood plywood (on 400mm centres)

 

[Harry_W]

Thanks for the suggestions everyone!