Subfloor Replacement Cost Calculator

Subfloor replacement typically costs $3 to $10 per square foot installed, so replacing a small bathroom subfloor (~40 sq ft) often runs a few hundred dollars (subject to a ~$400 job minimum), and a 200 sq ft area about $800 to $2,000. The base rate covers tearing out the old sheathing and installing new panels, and it's driven by the sheathing material (OSB ~$4/sq ft is cheapest, CDX plywood ~$4.60, engineered AdvanTech ~$5.40), the floor level (an upper floor between finished ceilings adds ~20%), the room (bathrooms and kitchens add ~25% for working around fixtures), and — the big variable — whether the joists beneath also need repair (sistering adds ~$2/sq ft, replacing joists ~$5/sq ft). Removing the old finish flooring, hauling debris, and adding a moisture barrier stack on top. Only the rotted or damaged section usually needs replacing, not the whole room. Enter your area and conditions above for a localized estimate.

The subfloor is the structural layer of sheathing — typically plywood or OSB panels — fastened across the floor joists that forms the base for your finished flooring (tile, hardwood, laminate, vinyl, or carpet). It carries the load of the floor and everything on it. It needs replacing when it's damaged, most commonly by water: leaks from plumbing, toilets, dishwashers, washing machines, or roofs; long-term moisture from a damp crawlspace; or flooding, all of which cause the wood to rot, swell, delaminate, or grow mold. Other causes include termite or pest damage, structural sagging, and persistent squeaks from a failed or loose subfloor. A spongy, soft, or sagging floor is the classic sign the subfloor underneath has gone bad. Because the subfloor is structural, a failing one isn't just cosmetic — it affects how safe and solid the floor feels, and left unaddressed the damage spreads to the joists.

Common warning signs include floors that feel soft, spongy, or 'bouncy' underfoot; sagging or uneven areas; new squeaks and creaks; finished flooring that's loosening, cupping, or popping up; cracked or shifting tiles; and a musty smell or visible mold, especially in bathrooms or near appliances. Water stains on a basement or crawlspace ceiling below the floor are another clue, and a soft spot right in front of a toilet or under a dishwasher points to a specific leak. To confirm the extent, the finished flooring usually has to come up so the subfloor can be inspected and probed for soft, rotted spots. Often only a localized area around a leak is bad while the rest is sound, so a contractor cuts out and replaces just the damaged section rather than the whole floor. Catching it early — when it's a soft spot rather than a collapsed area — keeps the repair small and stops the rot from reaching the joists.

All three are code-approved and widely used, differing in cost and moisture resistance. OSB (oriented strand board, ~$4/sq ft installed) is the most economical and very common in new construction — strong and consistent, but it can swell more at cut edges if it gets wet and dries out slowly. CDX plywood (~$4.60/sq ft) costs a bit more, holds fasteners well, is slightly stiffer, and tends to handle occasional moisture and drying a little better. For wet-prone areas like bathrooms and kitchens, engineered moisture-resistant panels such as AdvanTech (~$5.40/sq ft) resist water absorption and swelling far better than standard OSB or plywood — well worth the premium where leaks are a real risk, since the whole reason you're replacing the subfloor is usually water. Whatever you choose, match the new panel's thickness to the existing (commonly 3/4 inch) so the finished floor stays level. This calculator prices all three so you can compare.

Not automatically — joist repair is separate and depends on what's found once the subfloor is removed, and it's the single biggest swing in the cost. Often the same water or pest damage that ruined the subfloor has also reached the floor joists beneath, and those must be addressed before new subflooring goes down, because the joists are what actually support the floor. Minor cases are handled by 'sistering' — bolting a new joist alongside a damaged one to reinforce it (about $2/sq ft in this calculator) — while badly rotted joists need full replacement (about $5/sq ft), which is more involved because the crew may need to temporarily support the floor while swapping them. If the joists are sound, you only pay for the subfloor itself. Because you can't see the joists until the subfloor is open, budget a contingency for possible joist work on any water-damage job — it's a common surprise. This calculator lets you set the joist condition so the estimate reflects sistering or replacement.

Yes — to replace the subfloor, the finished flooring and any underlayment on top of it must come up first, since the subfloor is the structural layer beneath everything. If you're replacing the flooring anyway, this is a natural part of the project. If you hoped to save the existing floor, that's usually not possible over the repair area: the boards, planks, or tiles have to be pried up to access the panels underneath, and most flooring — especially glued or nailed tile, sheet vinyl, and engineered click-lock — rarely comes up cleanly enough to reinstall. Solid hardwood is occasionally salvageable by a careful installer, but expect some waste. So plan for new finished flooring over the repaired subfloor as part of the overall budget, and factor the finish-flooring removal add-on (~$1.50/sq ft) into the subfloor job itself. Where the damage is localized, you only remove flooring over the section being repaired, not the whole room.

Yes, and it's common and cost-saving. When damage is localized — rot around a leaking toilet, under a dishwasher, or near an exterior door — a contractor can cut out and replace just the affected section rather than the entire room's subfloor. The new panel is cut to land on the joists, supported at the edges (sometimes by adding blocking between joists so the seams don't flex), and fastened flush so the surface stays level for the new finished floor. The keys to a lasting partial repair are removing all the wet or rotted material — not just the obviously ruined part — and fixing the moisture source first, or the problem returns. For widespread damage, or a floor that's soft in many spots, replacing the whole room's subfloor gives a more uniform, reliable result and avoids a patchwork of seams. This calculator estimates whatever area you enter, so you can price a small patch or a full room.

For a localized repair like a single bathroom or a damaged section of a room, subfloor replacement is often a one-day job: removing the finished flooring, cutting out the bad subfloor (and any rotted joists), then installing and fastening new panels. Larger areas, whole rooms, upper floors, and jobs that also require joist repair or working around fixtures take longer — sometimes two to three days. Remember you'll also need time to install new finished flooring afterward, which is a separate step. If mold or significant water damage is involved, additional drying and remediation may be needed first, and the moisture source has to be fixed before anything is closed up or the rot returns. A contractor can give a firm timeline once the finished floor is up and the full extent of the damage — including the condition of the joists — is visible, which is why the final scope sometimes isn't clear until demolition starts.