Levelling a chipboard floor ready for glueing overlay flooring

[Stephen H]

Hi everyone, I have a chipboard floor on to which I want to glue some 1/2 thickness overlay timber flooring. But the floor isn't level.

The total area is some 7m x 5m. There are a number of small depressions (~3 or 4mm over a metre or so), but there are two irregular pond-like depressions, each about 1.5m on a side and curving down to about 10mm deep at the centre. I've been looking for ideas for levelling the ponds, and I'm getting different/ contradictory views from the various trade suppliers.

I had hoped to use a self-levelling compound (in-particular Bostik UltralevelHD over Bostik UltraNPPrimer), but one rep says that it won't have the flexibility for use on chipboard while another rep says it will (Bostik Sydney v Bostik Melbourne). I've been to a couple of home handyman stores and the sales staff looked at me as if I'm crazy to put cement on a chipboard floor - both claimed it couldn't be done and said that self-levelling compound was only meant for levelling cement floors.

Has anyone used self-levelling compound on chipboard flooring? Does anyone have any other ideas?

PS: I looked under the house to see if there's any structural problem causing the ponding - half of the floor area is supported by timber joists on brick piers, while the other half has the joists supported on RSJ - and both halves have ponding!!! Buggered if I know what's going on, so I decided to just fill in the ponds.

[SilentButDeadly]

I'd be willing to bet that either your chipboard floor is too thin (should be at very least 17mm) or your joists are too far apart for the thickness of your chipboard floor (no more than 600mm).

By the by........you should have piers then bearers then joists then floor. If you're missing anything then you may need a bit more than a bit of cement.

And no...I don't think cement on a chipboard floor is a good idea. A quick test - if you jump up and down on your chipboard floor and anything (house, furniture, wife, dog etc) shakes in response then your cement leveling compound is going to turn to powder over time...

[Stephen H]

Silent but Deadly said: By the by........you should have piers then bearers then joists then floor. If you're missing anything then you may need a bit more than a bit of cement.

Oops my omission - the floor is of course on joists resting on bearers resting on piers. The RSJ is a bearer for a section of the floor area. Chipboard measures at 19mm, and the joists are 550mm apart.

The floor is jump-up-and-down firm except for once spot where it can cause a perceptible wobble at the top of a lamp stand 1.5m away. Nothing noticeable though.

[Bleedin Thumb]

I thought joists were suppost to be 450 centres any way if your floors had gotten wet at any stage that could explain the depressions. Chipboard hates water.
The first thing that comes to my mind is replace the chipboard and if you are going to do that it may be worth looking at putting solid timber down?
I would be sceptical of a leveling product over timber but I'm not a floorer the product you described may work. Look it up on the manufactures web site and read the specifications.

[echnidna]

450 cts for 19mm chipboard and 600 cts for 22mm chipboard

[pawnhead]

You could try using a flexible tile adhesive: -

RLA - Flex 2 Part
RLA - Flex is a premium grade, flexible off-white 2 part ceramic tile adhesive designed to withstand movement in the substrate, where conventional adhesives are too rigid. It is designed for bonding all types of ceramic, stone and mosaic tiles, with the exception of light coloured and Green Marble, onto a variety of substrates like concrete, render, rendered brickwork, block work, Gyprock, plasterboard, fibre cement, particle board, and tongue & groove timber surfaces. It can be used internally or externally on wall and floor surfaces.
http://www.rlapolymers.com.au/adhesives.html#flex

You could probably just screed it as a leveling compound, but I wouldn't really know what the stuff is like.

[pharmaboy2]

Ardex K15 or Arditex slef levelling latex.

check site
http://www.ardexaustralia.com/produc...ay.asp?catid=2

they are both flexible - their data sheets will explain uses and best install method. Listen to the rep who was sus about it, I used a plain releatively cheap levelling compound, and it was a big mistake 18 mobths on - fortunately I'm pulling up the floor anyway, but I'll be using a suitable latex like product for the next time - might even use a tile on timber glue as they are very flexible also.

[Tools]

Pharmaboy is on the money.Ardit is for concrete,arditex is for timber.It works well,and is perfect for your situation.

Tools

[glock40sw]

G'day.
Arditex is the go. Seen pro installers use it for overlay all the time.

[Stephen H]

Glock40SW said: Arditex is the go.

I like what I'm hearing. Does it need priming for the glue, or can I glue right on to it?

[glock40sw]

I'm not sure.
You would be better off talking to the adhesive manufacturer.
I assume you will be using Bostik Ultraset glue?

[Larry McCully]

Steve, This is a common situ we encounter some times. Best thing to do is get a floor sander contractor in to crosscut the ply and level out the joins in the ply. This will reduce the hollowing in your ply quite a lot. It could that the ply is only expanding at the edges due to water penertration. After it has been sanded and it only needs to be sanded with24 grit and no finer, Then check the levels again. if you floor is more than 3mm depression over 3mt then get the ardetex in to finialize the level. use a longer stable when you secret nail 45mm instead of a 38mm. You will get the reach needed. It will be fine . Have fun............