Tongue and groove OSB and tongue and groove plywood are both code-rated subfloor panels, both carry span ratings, and both build floors that pass inspection and last. OSB is cheaper and it’s what most production builders use. That’s not marketing spin. It’s most of the subfloor market by volume.
The honest difference comes down to one thing: what happens when the deck gets wet. Everything else is a smaller margin than people claim.
Where OSB genuinely wins
Worth saying plainly, because a comparison that only lists one product’s advantages isn’t useful to anyone.
Price. OSB costs meaningfully less per sheet. On a large floor that’s real money, and on a tight-margin build it can be the deciding factor by itself.
Consistency. OSB has no voids, no core gaps, no patches. Every sheet is the same. Plywood is a natural product with graded veneers, and a cheap grade can have core voids that show up when you cut it.
Thickness uniformity. OSB is manufactured to tighter thickness tolerance across the sheet than plywood is. On a big floor that means fewer high spots to deal with before flooring goes down.
Availability in bigger panels. OSB comes in longer sheets more readily, which means fewer seams on a large floor.
If your build stays dry, gets roofed quickly, and is going under carpet or vinyl, OSB does the job and saves you money. Anyone who tells you otherwise is selling something.
Where plywood wins
Moisture recovery, and this is the big one. Both panels swell when they get wet. The difference is what happens after they dry.
Plywood swells, then largely returns to its original dimension as it dries out. OSB swells at the cut edges, and that swelling is substantially permanent, because the compressed wood strands relax and take on water, and they don’t compress back on drying. What you’re left with is a raised ridge along every panel edge that got wet.
On a subfloor, those edges are exactly where the seams are. The ridge telegraphs straight through vinyl plank, laminate and engineered hardwood. It’s the single most common complaint about OSB subfloors, and it’s usually not fixable without sanding the deck or pulling panels.
Plywood also dries faster, because water moves through it more readily. An OSB deck that gets soaked stays wet longer, which matters if you’re trying to close in a building.
Fastener holding. Plywood holds nails and screws better, particularly near panel edges, which is where subfloor fasteners live. OSB’s strand structure gives less for a fastener to grip, and edge fasteners are more prone to pulling through under repeated load.
Stiffness at the same thickness. Plywood is somewhat stiffer, so it deflects less between joists. Under tile, where deflection is the main cause of cracked grout and lifted tile, that margin is worth having.
Weight. Plywood is lighter sheet for sheet. Over a couple hundred sheets carried up to a second floor, your crew will notice.
The comparison in one table
| T&G plywood | T&G OSB | |
|---|---|---|
| Cost per sheet | Higher | Lower |
| Wet, then dried | Largely recovers | Edge swell is largely permanent |
| Drying speed | Faster | Slower |
| Fastener holding | Better, especially at edges | Adequate |
| Stiffness at same thickness | Slightly better | Slightly less |
| Weight | Lighter | Heavier |
| Thickness consistency | Varies by grade | Very consistent |
| Voids and core gaps | Possible in lower grades | None |
| Code-rated for subfloor | Yes | Yes |
So which one
Buy OSB when: the build is on a tight schedule with the roof going on fast, the floor is going under carpet or resilient flooring, the budget is the constraint, and the site is dry.
Buy plywood when:
- Tile is going down. Deflection and moisture both matter more, and the cost of getting it wrong is a floor you pull up.
- The deck will sit exposed. Renovations, owner-builds, anything where the shell isn’t closing in for weeks. Canadian build schedules run into wet springs and long shoulder seasons more often than not.
- It’s a bathroom, laundry, mudroom or kitchen. Anywhere a leak is a question of when, not if. A dishwasher that lets go onto a plywood deck is a cleanup. Onto OSB it’s often a subfloor replacement.
- It’s over a crawlspace or an unheated space. Sustained humidity from below, year after year.
- You’re a DIYer working slowly. No shame in it, but a project that takes months means a deck that sees weather. Plywood is far more forgiving of that.
- Long-term matters more than first cost. Your own house rather than a spec build.
Things that are the same, whichever you pick
Don’t let a panel choice distract you from the parts that actually cause callbacks:
- Glue every joist. Nails alone will let panels move and squeak as framing dries. This matters more than the panel.
- Gap the panel ends 1/8″. T&G long edges are self-spacing, the ends are not. Butt them tight and the floor ridges, and OSB will ridge harder, because it swells more.
- Fastening schedule is the same. 6″ on centre at edges, 12″ in the field, ring-shank nails or subfloor screws, confirmed against your requirements.
- Stagger the end joints by at least one joist bay.
- Cover it if the roof isn’t on. Both panels are better off dry. See how to install a T&G plywood subfloor for the full sequence.
The straight answer
If price is the constraint and the floor stays dry, OSB is a legitimate choice and it isn’t a compromise on code or structure.
If the deck will see weather, if tile is going down, or if it’s your own house and you’d rather not think about the subfloor again, plywood is worth the difference, and the reason is edge swell, not marketing.
Our tongue and groove plywood is a 3/4″ T&G CDX pine panel, and we carry CDX, exterior and pressure treated alongside it. Have a look at our full range, and spec the panel against the job rather than against the sheet price.
Working out whether the plywood premium is justified on your floor? Contact us. Tell us the finished flooring, the build schedule and whether the deck will be exposed, and we’ll give you a straight answer. To price the panels, request a quote.
