The short version
- Plywood: the best base for most floors.
- OSB: common in newer homes and fine when dry. Swells badly if it gets wet.
- Particleboard: not a good base for hardwood, and it falls apart when wet.
- Concrete: needs moisture testing and often levelling.
| Subfloor | Where you see it | Before new flooring |
|---|---|---|
| Plywood | Many older and newer homes | Screw down squeaks, check flatness |
| OSB | Newer homes | Check edges for swelling from past leaks |
| Particleboard / underlay board | Under older carpet and vinyl | Often removed or covered for hardwood. Not good when wet |
| Plank board subfloor | Older homes | Check fastening; sometimes add plywood |
| Concrete slab | Basements, condos, ground floors | Moisture test, vapour barrier, level |
Red flags we look for
- Soft or spongy spots (rot, water damage).
- Swollen OSB edges.
- Black staining (old leaks, mould).
- Big dips around toilets, dishwashers and exterior doors.
Common questions
Is OSB or plywood better for a subfloor?
Both are common and work well when dry and properly fastened. Plywood tends to handle moisture better. OSB edges swell if they get wet and don't fully recover.
Can you install hardwood over particleboard?
Generally not recommended. Particleboard doesn't hold nails well and breaks down with moisture. It's usually removed or covered with plywood first.
Who's writing this: Rose and Thorn Flooring is a flooring company in Surrey, BC. We install floors for a living, so yes, we'd love to do yours. But nobody pays us to say nice things about a product, and we don't earn commission from any brand. If something here is wrong or out of date, text us at 604-716-4160 and we'll fix it.