Cupped Floorboards

On the contrary, it is most likely a drying out effect.

The way the boards were cut from the tree means that there is a tendancy for them to cup as they dry - look at the end grain of a board at it becomes obvious. Most likely your house has had central heating added (and possibly new windows) which has significantly reduced the moisture content.

AWEM

It happened when cheap floorboards meet central hearing.

Pre 1950 central heating was a rarity, and so winter RH levels never plummeted to the depths they do today.

Wood cut in any direction except straight towards the heartwood (true quarter sawn) will always cup as the humidity changes. This is due to the fact the the wood cells are aligned, and expansion and contraction is not isomorphic at all..being least along the grain, modest in the direction between the heart and the bark and huge in a circumferential direction.

You can see this in cut logs. They will shrink and split radially almost always, rarely tangentially, and never *across* the bole.

|!> There's no smell of damp and no evidence of moisture, though one |!wall |!> does get a little condensation on it. |!>

|!> Do people live with it or should I get it sorted. Am concerned down |!> the line that a buyer or surveyor might think it's damp. |!>

|!> Thanks, Ed. |!>

|! |!On the contrary, it is most likely a drying out effect. |! |!The way the boards were cut from the tree means that there is a |!tendancy for them to cup as they dry - look at the end grain of a |!board at it becomes obvious. Most likely your house has had central |!heating added (and possibly new windows) which has significantly |!reduced the moisture content.

Your 1940s floor boards will be thick enough to sand level with a power sander, if you wish.

Thanks for taking the time to reply, chaps. The house does have CH and DG so those answers would be spot-on.

Regards, Ed.

If it really concerned you, you could sand the floor flat if the amount is not too much, otherwise they *could* be lifted and run through a planer.

An alternative would be to advertise this as a character feature when you sell.

It can be caused by running a dehumidifier in the house. You end up with significantly different relative humidity in different rooms. Have you done this?

I haven't. I think the boards were pretty cupped when I moved in 3 years ago. I've probably just become more aware of it.

I certainly won't be getting a dehumidifier now, though! :)

Main thing is, the cupping is a one-off event.

Main thing is, cupping is not a one off event but happens on an annual basis as summer to winter humidity varies by a huge amount.

So gaps in floorboards should open and close with the seasons then? Can't say I've noticed it, and where boards have been lifted and re-fixed without gaps, they haven't swollen. The shrinkage of new timber in a centrally heated home is essentially a one way process in my experience

I have.

No. There is an initial shrinkage to more or less the average RH of the home, but in summer RH is very hight - maybe 70% - in winter it can be very very low indeed.

I had a friend whose father owned an old mahogany bureau with the top cut very near the heartwood. In winter it would curl up and leave an inch gap..in summer it was flat..

Roughly you may expect a 1% shift in dimenson around the grain , and

Cupping is caused by the difference between the 1% and the 0.5% which will happen in a plank cut near to the heartwood.

The figures are only about 10% of the shrinkage that happens from green to fully dried, and about 50% of the figure from kiln dried to fully dried, but they are still there.

Oh they do! The effect is much more pronounced in doors - fitting in the summer and tight in the spring

AWEM

That's outside doors.

Inside doors fit in winter and jam in the summer!

Exterior doors are different

Ever wondered how they dry timber in the tropics with permanently high humidity?

I can't say it's ever been the sort of thing to keep me awake at night, no..

Well, sufficient to say that high humidity doesn't stop things drying. All this humid weather we have in summer, and the clothes on the line still dry. Similarly, wood continues to dry at 100% humidity if the temperature is high enough. I saw a graph explaining all this somewhere. I didn't understand it but it looked convincing :-)

Yes but the temperature will have to be above the local boiling point won't it?

Our wood dryer runs at 150C ;-)

AJH

I have never seen wood dry underwater, which IS 100% humidity..