Floor cupping need expert advice

[TrewtoTradition]

Ok black butt timber flooring laid about 6 months ago wide boards about 140mm room area is about 5m x3 m.The floor has been layed on 100x40 joists which are held in place by stirrups as there used to be an old slab there so some of the floor is on 100x 45 and other spots its on 20x 45 battens there is little room under the joist maybe 50mm or so and there is no venting under the floor plus it’s a open plan bedroom with a bathroom at one end behind a timber wall. The entire floor has been painted white so all the boards are sealed.
I look at the bedroom today and every board has cupped dramatically and two of the boards have pushed up 200mm yes 200mm overnight we haven’t had any big downpours and under the boards looked dry.
Whatdo yareckon

[journeyman Mick]

If the boards have cupped (hollow on top) then the bottom suface has grown. This means the bottom of the board has absorbed more moisture than the top has. If you have only painted the tops of the boards and not the bottoms this may be causing/exacerbating the problem. Lack of sub-floor ventilation would also be a contributing factor.

Mick

[glock40sw]

G'day.
Is the whole floor cupped or just one section?

Is the Batten section cupped or the B&Joist section?

Get under the house and see if you have a wet patch or leaking pipes.

[Skew ChiDAMN!!]

200mm? Lessee... that's 20cm or around 8" :oo: Surely you meant 20mm?

The probable reason's already been mentioned and I'll hazard a guess that it's the battened section lifting...? Still, I gotta ask: How long did you store the boards in the room before laying? ie. Did you leave 'em in a stickered stack for any length of time?

[TrewtoTradition]

yes journeyman Mick thats exactally what i thought.thanks

glock40sw yes its the whole floor every board is concave,but joist and batterns are fine.


And yes i mean 200mm when icut the board out with a jigsaw the gap closed up instanly

Ill try and attach pic

[TrewtoTradition]

Heres a pic of the sub floor before the flo:~or went down.

[glock40sw]

How long has the floor been down?

How long has it been cupped?

How old is the concrete where the stirups are?

Is there a moisture membrane under the battens?

For the whole floor to be cupped with that much pressure on the boards, I'd say you have a very bad moisture problem somewhere.
Either moisture from outside is getting under the floor or you have severe pipe leakage.

Go buy a moisture meter (even a cheap one will do). test the top of a board and note the reading. then test the bottom of the same board. They should be the same give or take 1/2 to 1%. If the bottom is wetter than the top, then you do have a underfloor moisture problem and no amount of insitu climatisation will solve it.

[TrewtoTradition]

How long has the floor been down? 6 Months

How long has it been cupped? not sure say 1 month

How old is the concrete where the stirups are?

some stirups are boted to an old slab that was originally there others have been dug into soil


Is there a moisture membrane under the battens? Yes

[glock40sw]

How long has the floor been down? 6 Months

How long has it been cupped? not sure say 1 month

How old is the concrete where the stirups are?

some stirups are boted to an old slab that was originally there others have been dug into soil


Is there a moisture membrane under the battens? Yes


So...what has changed in the 6 months that the floor has been down?

For the floor to be as bad as you say, it would have happened within the first 3 weeks after installation. Not 6 months later.

[Extracare]

There's a big pipe running under the floor in that photo. Possibly leaking?

[China]

As said above I'd be checking the waste pipe and install underfloor vents while your at it