Floorboard warp/cupping, Insulation?

[TheRoost]

In the autumn I started to notice that I could see & feel the 'ridges' of the floorboards through the upstairs carpets, what I mean is the boards seem to be warped/cupped and this is visible through even a thick rubber underlay and thick carpet. I don't remember seeing it when we moved in back in August, so wondering if they move when the temperature/humidity changes, and heating is on more? They are 5" original plain pine boards.

Downstairs we are planning to have bare floorboards (currently carpeted) and are thinking about insulating between the joists from underneath. If I pull back the carpet at the walls, the boards are obviously cold, musty and feel not exactly damp, but not bone dry either, from the moisture in the air passing under the subfloor.

If we remove the carpets, and fit insulation underneath the boards (i.e. boards become shielded from outside air, but also exposed to central heating) are the boards likely to dry out a lot and warp? would be interested in your experiences in uncovering floorboards and/or fitting insulation.

Andy

 

[Penners]

Wood boards are always vulnerable to cupping if one side is more accessible to damp than the other side. In the case of your floorboards, the underside is almost certainly unfinished and exposed to a damp atmosphere, whereas the top is probably varnished and exposed to drier air. So the "skin" of the underside of each board tends to get damper than the top and swell, causing the cupping.

Your idea of insulating the underside of the boards will be helpful, but I also advocate painting/varnishing the underside of them, too, with the same surface finish that you use for the top. This is called a "balancing" coat and helps to do just that - balance the ingress and egress of moisture on the two sides of the boards. There's no guaranteed way of eliminating cupping, but this will certainly help to minimize it.

Also make sure that each board is nailed/screwed down with two fixings, one near each edge of the board, on every joist.

 

[TheRoost]

Thanks Penners, I would never of thought of that - perhaps i'll remove the carpets and allow the boards to acclimatise for a few weeks, then coat the undersides of the boards at the same time as doing the top, fitting the insulation last.