How to deal with a "wonky" floor

[TonyW]

Removed an old laminate floor (downstairs) from my daughters new property which was built in the mid 80's. The property is timber framed. I was a little surprised to find chipboard flooring underneath (expected to find a concrete base). The chipboard has been laid to cover the whole of the downstairs and the walls built over this.

The flooring in general does not seem to have been too well laid - there are some quite large spaces between boards (not enough to reveal what's underneath). Also cannot so far find any evidence of fixing (no nail or screw heads!).

I am intending to replace with new laminate but have found a couple of problems with the chipboard floor and would appreciate some advice and views on quickest way to fix the problems which are:

1. One board in particular has become convex down most of its length. Do not understand how/why this has happened. I did remove a length of telephone extension cable which had been forced down the gap between boards - could this have caused the bowing over time?

2. In the hall there is a definite dip between the end of two boards.

Apart from these issues the floor feels very solid - no bounce etc.

So looking for ways to fix - without trying to relay the whole floor! Original thought was to use self levelling compound which would probably be ok on the floor area that has dipped but would not work on the convex length of board.

Any advice / suggestions much appreciated

Cheers
Tony

 

[MooreToolsPlease]

I would try and locate the joists and screw the convex board down.
the 2 boards that dip, I would more than likely cut out a small ish hole to see what joists are in the surrounding area
then cut out a reasonably sized piece and then put in noggins to support the pieces.

 

[Keith Smith]

It sounds like they haven't left an expansion gap round the edge and the board has expanded and flexed up or down.

I would check that there is a gap round the edge


Then cut a hole in the floor big enough to have a good look through. It's easy enough to reinstate afterward just screw battens round the edge of the hole and screw the piece you cut out back in place (into the battens)

 

[TonyW]

Thanks for the replies

Will check out the things you mentioned - definitely need to cut a hole to see what is underneath etc.

I just find it strange that there is no sign of fixing nails or screws!

Cheers
Tony

 

[devonwoody]

might have been tongue and grooved chipboard.Particulary if it is around 18" wide.

 

[Woody Alan]

It is possible it's a floating chipboard floor over concrete hence no fixings. if they didn't let the floor dry enough and layed it poorly that would explain the movement. Mid 80's ought to have insulation/polystyrene under the concrete but I am not sure of the timeline re building regs, although it ought to have something, if you have polystyrene on top of the concrete and your floor is on the styrene it would explain no fixings and some movement as styrene gives in wear area. This wouldn't explain the walls being built on it. Unless they are not and it just looks like it because skirting laid over edges. I would not cut out a big hole yet, just use a sacrificial wood bit say a 1/4 inch and drill through the chipboard and see what you hit, do it in a corner though.

lastly if you don't want to get too involved and you want to cure bounce make an adequate size hole and pour thin epoxy resin into the hole so it moves by capilliary action to fill the gap, a trick used by caravan dealers to repair laminated caravan floors.

Alan who is not a bulider and not qualified to advise.

 

[TonyW]

dw Yes it is T&G chipboard

Woody Alan Not had chance to check yet (dealing with the upstairs boards at the moment!!) but it does seem that its the floating type as you describe. From a brief look where I have moved skirting boards there is some polythene sheeting (assume this laid as damp proof) do not think there is any polystyrene on top of concrete. I am fairly convinced that walls have been built on top of the chipboard floor - so far!

Like you suggest will drill a small hole first to check what I hit. Although I am quite tempted to use a toy I bought some time ago - a Trend hole cutter - which cuts a large diameter hole in chipboard flooring and with the use of a plastic ring allows the offcut to be replaced as an inspection chamber.

I suppose the worst case scenario it to cut this board out and replace - it could not be in a worse position as it runs from the hallway to under the door leading to the lounge with two walls built over. If there had been joists anywhere may have been able to pull it back down by screwing into them.

Cheers
Tony

 

[TonyW]

Finally had a look under the floor and can confirm that it is a floating chipboard floor over concrete. There is a layer of polystyrene and on top of that polythene sheet then finally the chipboard.

So it seems I am left with a couple of choices:

1. Remove and replace the offending convex board. This is something I was trying to avoid due to its position under two walls :x

2. Try and fasten the board pull the centre down. I have some concerns if this is a viable option:
a. What are the chances of this working (estimated 10mm) and staying put?
b. What would be the best method of fixing?
c. By fastening through the chipboard into the concrete would I be compromising the damp proofing?

Hope that someone may have an answer or alternative suggestion

Cheers
Tony

 

[RogerS]

Maybe rout/cut the offending board to relieve any pressure forcing it up. Then I'd probably drill a couple of screws on each board through into the concrete..sticking a bit of silicon on the end of the screw. If you use a masonry screw then you don't have to worry about trying to squeeze the wee plastic thingie through the board and down into the concrete.

Re damp..would have thought that there would be a dpc under the concrete and so you're not going to let in any damp. Even if there isn't a dpc under the concrete, you've got a thick layer of polystyrene between your board and any damp. (Maybe the poly sheet you see is a vapour barrier?)

(Roger - who isn't a builder)

 

[Keith Smith]

It's very strange for one board to flex up unless it is exposed to damp underneath :?

Have you checked if there is an expansion gap round the edge? You need 10mm at least, if you don't have a gap and pull this board down another will just pop up. Plus I don't think it would be wise to try to screw it down anyway.

If you have an expansion gap first thing I'd try is kerfing the top of the board; use a circular saw to cut a couple of slots as deep as you can without going through the polythene the full length of the board and see if that lets it lay flat.

 

[devonwoody]

And then sit something very heavy on it for a week.

 

[TonyW]

Thanks for you replies

Maybe rout/cut the offending board to relieve any pressure forcing it up..... Even if there isn't a dpc under the concrete, you've got a thick layer of polystyrene between your board and any damp. (Maybe the poly sheet you see is a vapour barrier?)

Think that routing the board along the length is a good idea - I hope this will be enough to relieve any pressure (still trying to avoid screwing it down).

t's very strange for one board to flex up unless it is exposed to damp underneath :?

Have you checked if there is an expansion gap round the edge? You need 10mm at least, if you don't have a gap and pull this board down another will just pop up. Plus I don't think it would be wise to try to screw it down anyway.

If you have an expansion gap first thing I'd try is kerfing the top of the board; use a circular saw to cut a couple of slots as deep as you can without going through the polythene the full length of the board and see if that lets it lay flat.

I too thought it strange for the upward flex. There are however signs of previous water leaks in the kitchen from the washing machine and in the lounge from the central heating install. Perhaps this partially responsible.
I have seen expansion gaps in other areas of the room, however it is difficult to see in this particular area due to it being near an under stairs cupboard.
I intend to rout the board as you suggest - assuming 18mm board was thinking rout to a depth of 15mm - hopefully this will be enough to allow the board to settle back flat.

And then sit something very heavy on it for a week.

Do you think I should ask SWMBO

Cheers
Tony