Advice needed on sanding cupped boards

4 Nov 2007
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United Kingdom
Can anyone with hands-on experience tell me if sanding will effectively flatten a pine floor where the boards are cupped? I have never used an industrial sander, so don't know how effective they are. I want to lay carpet tiles or laminate onto the boards, but not raise the floor level. The cupping produces ridges in the order of 1 to 3mm. The area is only 3.6 x 1.7 metres.

Except for this hallway, I've replaced all downstairs t&g with ply and P5 chipboard. The staircase makes it tricky in the hall. I have begun screwing down the board edges, but that doesn't remove the cupping. If I can get away with sanding, that would be preferred. If advised that this won't work, then I'll replace with 18mm sheet material.
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Thanks - so it's replacement I guess and some fiddly work under the bottom stairs. I have to say that all the 1960s t&g floorboards in the house were permanently cupped, whatever the season. Upstairs floors are still that way (and can stay carpeted!)
I would say it depends on the circumstances, the original victorian floor boards in our bedroom were permanently cupped regardless of seasonnal changes( I know cos it took me three years to get round to sanding them after i had thrown the carpet out). they have been sanded for over three years now and are still as flat as the day they were sanded with no signs of further cupping nor crowning.
In essence i would say it is probably worth sanding an old established floor that is permanently cupped, but would be wary of doing so to a new floor that has started to cup.
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Many - We've sanded 100's of floors over the past 30 years and, whilst it's always a gruesome task, it can often fix a problem like yours. Your 1960's cupped boards (pine?) should respond well to being sanded ... my guess is that they chosen because of cost not quality and so probably cupped not long after they were installed (or even before). Your 1 to 3mm cupping should come off well and leave a flat surface. Sanding your floor is less disruptive than swapping it for ply 'cos of your staircase. Mind that depends on how the staircase is installed ... it is possible to jack-up staircases very slightly - ¼" to ½" (we use a bottlejack and a couple of 4" x 4" timber pins) so you can remove old flooring from below it and slip-in new stuff. The staircase is then lowered back into position. This is our preferred method when fitting solid floors (secret nailed) as it avoids that awful beading look or gaps.
Thanks! It's great to be able to tap into so much practical experience. I was just about to pick up the P5 boards (which is not much fun in my coupe.)

I will see what sanders I can hire. Ther area is small so lots of edges. Brandons do an edge sander, and a 100mm belt sander. Not sure which will be best - I don't care if the floor surface looks scratched, so long as it is reasonably flat. Should I work across the boards at 45 degrees?
The area is small so lots of edges. Brandons do an edge sander, and a 100mm belt sander. Not sure which will be best

If you have lots of awkward cutting in to do, Bosch, Fein and Westphalia all make a useful 'delta head' sanders for those awkward corners. So long as you remember these aren't heavy duty enough to do your main floor .

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