Preparing a chipboard floor for painting

I want to paint a new chipboard floor, I've filled the cracks and screw holes with caulk, I think it needs a primer. Is there anything specific that I should use or will a general purpose undercoat do? I was looking for something a little thicker than paint that would fill any of the larger gaps but those products are much more expensive. It's a low traffic area (bedroom). Any tips?

Normally chipboard in an ordinary non wet environment does not need to be waterproof. Here in Brittany especially in properties that are old, poorly ventilated or heated, or occupied only in winter months there is a danger of chipboard swelling due to the high levels of humidity that can apply. In normal circumstances if you have to or want to use chipboard then it would be better to use a bathroom grade - but personally I would not use it even in a bathroom. There is no real way to make a sheet of chipboard fully waterproof. Better to use ply as has been said, and then I would use marine ply. It's much stiffer and moisture resistant. I would use screw fixings. Decoration of ply is easier too but again watch the grade and avoid stuff like shuttering ply. As I have said before I would counsel use of an applied finish.

No you read the 1st paragraph.

David Rosemont said:

"did you use bathroom grade?"

James replied:

"No I didn't, if the paint is decent enough will it not be waterproof?"

Well, I have read the first page AGAIN and James says "new chipboard floor" none of the comments ask if it was P5, P6, or anything else, and James doesn't clarify further, hence I ASSUMED he used normal Chipboard Flooring, which is usually T&G, and which to my simple knowledge is Tongue and Grooved flooring to be used to walk on, subject to various BSI/CE recommendations on support, pitching, etc.

Yes I agree 22mm is better, if its available in France, and I always go for P5 rather than P6 as the prices (in UK) aren't much more.

Assuming you didn't read the first page of the thread other wise you'd know it isn't P5.

Yes it can remain solid but just like shelves in kitchen cupboards they sag that is why Caberfloor recommend additional plywood before tiling.

22mm is better than 18 so should stay flatter longer.

Assuming you used T&G flooring grade chipboard (ideally P5 bathroom type) I'm struggling to understand why it's unsuitable. The T&G flooring chipboard I have in my Bungalow in the UK has been down for 28 years and still as solid as a rock. The T&G chipboard flooring put on the joists in my Lounge in France by the previous owner is also as solid as a rock, although I was going to cover it in either Lamininate or wood veneer flooring to make it look better.

Yes, flooring grade chipboard looks cheap, it is unattractive, but it works. A coat or two of PVA wouldn't go amiss but obviously any paint or covering which didn't have any wear resisting properties would quickly fail depending on traffic, but then you would expect that. Perhaps something like 'Deck Paint' would work ?, I've used it on Fibreglas and Marineply and it wears and stays on well.

Ooh, the rubber wood sounds nice. I guess it would be pretty water resistant too. Is it easy to get? I have to refloor a mezzanine as the previous owners did it in very thin pine planks and it's quite saggy. Any idea what the per m2 cost is and where to get it in France? Thanks.

You used to be able to get large flat sheets of yacht decking which is great in a bathroom- I did one for a rather famous person once. No names no pack drill. Expensive though!

Thanks Pauline, I'll have a look.

Our bathroom floor is lino but that was laid over plywood, as recommended by the manufacturer. If you want a hard floor, have you considered rubberwood? This is known in France as hévéa. You can get it in tongue-and-groove planks formed from blocks. We bought ours in the UK because at the time it was cheaper - also far cheaper than oak or bamboo. It is an overall goldy colour with attractive gnarly patterns in the wood and is hard as iron. You can use an underlay for sound insulation. We have this in bedrooms and landing and it looks wonderful. Some day we'll get around to installing skirting boards.

Thanks Peter, good suggestion but I am confident that it will provide suitable structural stability as it has not deflected at all since installation some time ago even though it has undergone extensive and varied use. The boards are thick, screwed and glued on very stable and closely spaced joists.

Looks like more of the ticket and not expensive either. The polished concrete look is another in thing. Takes me right back to the Corb days.


Great product but does not deal with the core issue that the underlying chipboard floor is unsuitable.

For this product to be effective, which in itself has no structural strength, you need some other suitable material. Cheapest is plywood sheets provided again it is thick enough that they do not sag.

May I suggest you discuss this with Leroy Merlin before you buy the product.

Sounds like my father's carpenter Terry who did things like that regularly. Left his wellies in the middle of a fresh floor, used his shovel to grab a joist, hauled himself up climbed along the joist, went down and was standing looking at his boots. Len, my father's partner, asked him why. "Oh it's loik dis. If I had walked back out, I would have made footprints roit across de floor. So now I can cut them off when its droi, fill in de hole with fresh stoff and level it off". The building trade is full of excellent acts who never make it on stage! Anyway, he was a brilliant carpenter but what the hell was he doing laying floors when that was my old man's job as a rule?

Thanks David, sounds like an interesting profession!

I'm thinking of using this now

It's probably not going to amount to much provided that reasonable domestic loading is adhered to. Once I had a client who, without telling me in advance, nstalled a slate bed billiard table on a simple loft floor and we had to get the floor strengthened to make sure it didn't end up further down. The same client's wife rang me one day to tell me that the extension we had started building was the wrong size. I checked the drawings but to be sure I went down to site, 50 miles each way. I got there and everything seemed fine. She siad "No David it's the wrong size". I explained that we had checked everything and it was in order. She beacme quite excited and it emerged that the furniture she had bought in a sale at Harrod's that week was too large. Her husband agreed that the building should be demolished and made a bit larger! On another occasion I had a client who rang me up to say that there were some strange noises in his house, which we had never seen or had anything to do with. One of my guys went down to find that the client had removed some of the roof truss members to improve accessibility and then stacked literally tonnes of dead paper filing in the loft all resting on 4x2" ceiling joists. The place had to be evacuated, shored up and strengthened. Over my years in the profession I can tell you some really hair raising stories. Not relevant to this but I had one client whose decapitated head was found by the side of a motorway, but they never found the body. A pair who turned out to be serious criminals not above murder. Another who disappeared on the run from Interpol. On floor supports I once saw an Irish demolition labourer standing on the free end of a three floors up single cantilevered timber beam sawing away at the only support. I asked him in rather alarmed tones to stop immediately. He replied "Ah sure Sir! 'Twas only to make the joint open up to make the sawing easier!"

I would be happy with vinyl, what do you think about sagging? They have been in place for months and used as a storage area and there has been no noticeable movement so far.

With respect James.....the fact that the joists are at 400 centres is even more reason to have staggered them. It makes it even easier to acheive. It makes every subsequent activity much more stable. A certain amount of movement will always take place and staggered joints mitigate this effect. For example, if the joist you are joined on either rises or falls as it dries out the joint will be exagerated. Whereas if staggered the effects are spread out and usually remain undetectable...

Wow those are some joists! I still thinl you will be better with another finish!

Some food for thought thanks everyone. It's 22mm by the way and the joins are directly on top of the joists which is why I didn't stagger them. Joist are 10cm wide at 400mm centers.