My old subfloor has some soft spots - should I repair or replace it before installing new floors?

You absolutely need to address those soft spots before installing any new flooring. Soft spots indicate moisture damage, rot, or structural weakness that will only get worse and could cause your new floors to fail prematurely.

Identifying the extent of damage is the first step. Soft spots in subfloor are typically caused by water damage from leaks, poor ventilation, or moisture infiltration. A licensed contractor should inspect the affected areas to determine if the damage is surface-level or extends to the floor joists below. They'll use a moisture meter to check current moisture levels and may need to remove sections of subfloor to assess the underlying structure.

Repair versus replacement depends on the severity and extent of damage. Small isolated soft spots (less than a few square feet) can often be cut out and patched with new plywood or OSB subflooring. However, if the soft areas are extensive, if there's any mold present, or if the floor joists are affected, full replacement of the damaged section is necessary. In Ottawa's climate, moisture issues are common in basements and areas near exterior walls, so thorough remediation is crucial.

Proper repair involves several steps beyond just replacing the subflooring. The underlying moisture source must be identified and fixed first - whether it's a plumbing leak, poor vapor barrier, or inadequate ventilation. The subfloor replacement must match the existing thickness (typically 5/8" or 3/4" plywood/OSB) and be properly fastened to joists. Any height differences need to be leveled, and in some cases, a moisture barrier or additional underlayment may be required.

For your new flooring installation, addressing subfloor issues now prevents costly callbacks and warranty problems later. Most flooring warranties are voided if installed over damaged or inadequate subfloor. The Ontario Building Code requires subfloors to be structurally sound and properly moisture-protected, especially in below-grade applications.

For a thorough subfloor assessment and proper repair before your flooring installation, request a consultation from Ottawa Floor Install. Licensed contractors can identify all issues and ensure your subfloor meets manufacturer requirements for your new flooring.

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