Replace floor boards if plying over?

18 Jun 2018
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United Kingdom
We have a few floorboards here and there that have been taken up, either due to wood worm, plumbing or electrics.
We will be getting both laminate and carpet through out the house. Currently every single room is stripped back to floorboards, with all old woodwork removed too as we are renovating the house.

We have been advised we should ply over all the floors since we are renovating to give us a nice consistent flat solid floor for the new floors to go on.

As we are planning on plying over the whole floor. Would it be OK to skip replacing the floorboards that are damaged / missing? There are no large gaps. Just 1 floorboard width gaps here and there. Or should we still have them replaced and filled in? Its hard to find the exact size floorboards to fit in.

As for the ply. Would 6mm be OK or should it be thicker? Does it need to be a specific kind? i.e WBP, structure ply etc?

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6mm ply is not enough if there are gaps due to missing or damaged floorboards. It is just to smooth the surface and prevent draughts and dirt blowing through the gaps.

You must replace missing boards.
Thanks John.
What thickness would make it ok to not replace floorboards or should they really always be replaced.

Would cutting strips of ply or planks of pine be ok? We can't seem to find anywhere that sells the exact size of our floor boards. Even then I think it might be 1mm off. (19mm thick boards but sheets are 18mm)
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they should be replaced.

When faced with horrible chipboard flooring, I like to pull it up and put down ply straight on the joists.
18mm will do, but needs nogs along the joints as it is (usually) not T&G.

Putting that over your old floorboards would be wasteful expense, and would raise your floors meaning your doors and skirtings need cutting.

If using pine boards, you can plane them a bit thinner. Dry them first, as they will shrink.

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