OSB3 or Plywood subfloor?

Kitchen refurb is underway and I’m going to need to replace the existing sub floor (boards seen better days, some have vinyl glued to them, some have cork glued to them).

We’ll be laying a parquet floor on top.

Is OSB3 good enough or should I really be buying marine ply at twice the price?  Seem to read different thinks different places.

How about waterproof Chipboard flooring (Weyroc)

18mm thick T &G

If you do go with OSB – take the time to paint/varnish any cut edges.

Something like this:

https://www.wickes.co.uk/Wickes-P5-T+G-Chipboard-Flooring-18-x-600-x-2400mm/p/164516

Yep – that sort of thing. Might be cheaper at a builders merchants?

I wouldn’t have chipboard on any of my floors, never mind a kitchen or bathroom where spillages are more likely. I’d go with plywood everytime. Exterior not marine.

This is clearing things up nicely 🙂

No chipboard or osb. Decent 18mm far eastern ply/wbp. Doesn’t need to be marine ply as it shouldn’t be getting wet unless you have a lot of spills/leaks.

If appearance isn’t an issue, would exterior grade shuttering ply (same price as OSB, half the price of WBP ply) be good enough?

That’s not a recommendation, genuinely a question.

No need for ply, the flooring in your link will be fine

“marine ply” doesn’t really mean anything important unless your kitchen is in a boat you intend to have insured by Lloyds of London. It doesn’t have any miraculous waterproof properties its just a grade that the insurance industry recognises. If you applied it in applications where it needs to be waterproof you’d need to waterproof it. And the same goes for ‘exterior’ ply too – its designed for outdoor applications but the weather will ruin it if you don’t protect it

Moisture resisitant chipboard flooring is, as the name suggests, intended for making floors and is inherently water resistant, not just on the surface but all the way through. And it will be in better nick if it happens to get wet than either OSB or Plywood. I have it down on the floor in my workshop and it survived being submerged under several inches of water for a few days after the burn burst its banks. Had to throw out all the OSB and plywood I had standing in there though. Other grades of chipboard would turn to weetabix if they got wet but the green-tinted MR boards for floors are fine.

the mr weyroc is not tinted now – i think its all MR now.

I left a few offcuts outside after a job, still solid after much wetness.

As Mcc says, P5 chipboard will be fine – also a lot less wasteful than sheets of ply which are ok as long as everything is 400 centres, square and parallel. 18mm is minimum for structural but you can go for 22mm if you want something that feels sturdier as you’ll no doubt end up hanging some joints between joists

If you’re having parquet laid on top, for heaven’s sake, make sure your joists are level before chipboarding – will make your parquet guy’s life easier and give you a tidier floor.

If it’s a subbie fitting the chipboard, make sure they screw it in instead of nailing. It’ll squeak like a bugger after a few years if it’s nailed. All screws (min 2.5x thickness of chipboard) should be countersunk just below the surface for parquet. A bead of PU (or a good glob of PVA) will help joints stay solid.

Cheers deadly.

Was planning on doing the sub floor myself. I’m taking the existing boards up this week so will check joists before laying. If they’re not level, any tips on how to level then?

Also, think there’s some concrete so it’s not all suspended for. Think I’ll need to take that out and put some joists in that section.

any tips on how to level then?

Don’t shift them around too much crowbarring the old floorboards up! 🙂

They’ll probably be ok – if you’re screwing a sturdy CB floor on top you won’t have to worry about a few mm here or there – if it gets any worse than that then a few sheets of hardboard cut into long strips can be handy for packing out sheets of chipboard – but check first with a straight edge. Or with a laser that fires a horizontal line as well as a vertical – choose your datum joist (probably at doorway), switch on laser, measure using ruler to datum then quickly check the rest of them.

For plank floors, you get away with a lot more – but when it’s parquet, and the levels rise and fall, you get little gaps opening up between the short joints in the herringbone – unsightly if pre-finished and/or require a lot more sanding and filling if one of those type of floors.

Thanks for the tips.

The floor is 21mm x 100mm x 500mm tectonic Oak planks from Chauncey’s, pre finished… so don’t want to cock the subfloor up!

You don’t happen to know any fitters Manchester way do you Deadly?

Ha – Chaunceys?!?! They’re who I do all my sub-contract work for around Bristol. I’ve fitted quite a few of those 100 x 500 blocks. 🙂

Don’t know of anyone personally up that way I’m afraid. When is it you’re planning on having it done and how many sqm? Are the blocks pre-finished or is it a sand and oil on site?

Blocks being delivered next week or week after. Looking to fit 33sq metres at end of month/early April. They’re pre-finished.

YGM dooosuk!