Hello,

I have a 1920s house I am remodelling and got to the floor phase.
Decided for hardwood. Problem is that the upper floor sagged about
15mm (in the centre) over the years and I cannot push the floor back
up.

The hardwood planks are about 10mm thick and about 50mm wide and come
in different lengths.

Right now I am considering two options.

1) get laminated wood in several different thicknesses, cut strips and
screw them to the old floor trying to eliminate or, at least, reduce
the sagging to a minimum and then nail the hardwood planks to them.

2) pour self-leveling compound (a kind of cement) and then glue the
hardwood planks to the cement, as suggested by a friend, but I am not
very fond of this method.

Anybody has experience with this problem and how it was solved?

Thanks in advance!