Uneven upstairs floorboards

[pippo]

Hi,

A few months ago i gathered info from here about the unevenness of my ground floor floorboards. I used 6mm ply wood on top and the floor is looking nice and even now.

I am now moving onto the upstairs, up here unfortunately the floorboards are very uneven, some look newish and must have been replaced fairly recently. The originals are 22mm and i think the newer ones are 18mm which is obviously 4mm difference. When we moved in, it was very obvious even through the old carpet and underlay. I did plan to cover these with 6mm plywood like downstairs however i feel that over time it will just sag and show thru again.

I have considered even replacing the floors completely as all the skirtings and facings are off, however there are 2 old style partition walls that have wooden baseplates resting on the floorboards which will obviously cause difficulties to replace underneath.

So, I am thinking of boarding over with thick ply or hardboard or something lol. What would your suggestions be in this situation? If I should board over, what material and what thickness should I use? Or should i completely replace the upper floor and figure out some way to replace under the walls too.

Many thanks in advance for any advice.

Pippo

 

[WoodYouLike]

If the thinner boards are randomly installed between the thicker boards plying over it would always cause movement, echoes etc.
You could consider 'filling' the thinner ones first with hardboard strips and then ply over.

Or ultimately rip everything out and install load-bearing new floorboards (at least 18mm thick and joists not further apart than 35 - 40cm)

 

[pippo]

WoodYouLike,

would there be any problems if i was to lay thick (say 18mm) ply ontop of the boards? its 4 or 5 boards together that are thinner, and the rest is just generally uneven, broken where thwy have been lifted previously.

pippo

 

[WoodYouLike]

I would take the trouble to add hardboard sheets too where needed to make sure it won't turn into an echoing area.
Then you can screw down the plywood over everything (screws every 25 - 30cm)

 

[pippo]

ok I will do, thanks.