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Persistent squeaks, soft spots, warped or cupped boards, cracked tiles, musty smells, or cabinets that suddenly feel loose all point to a failing subfloor. When you spot any of these red flags, the subfloor’s structural integrity has likely slipped below safe standards and needs prompt replacement. 

A well-installed subfloor should last 50 to 100 years, so any early warning signs mean water damage, rot, or another hidden problem that a flooring pro should inspect right away.

You can layer a new subfloor over an old one only when the existing surface is perfectly sound—no dips, rot, or moisture damage. If there’s any doubt, remove the floor covering and underlayment and start fresh from the top down; replacing the subfloor from underneath is unsafe and rarely effective. 

Stacking a new sheet onto a flawless base won’t weaken the structure, but skipping repairs on a damaged layer can leave you with uneven floors and bigger headaches later.

Your subfloor is supported from below by sturdy joists and completed from above with an underlayment and finished flooring. The joists form a robust framework while the underlayment creates a smooth base for the visible floor covering. This layered construction guarantees maximum stability and durability, ensuring that every component contributes effectively to the overall performance of your floor.

Consider repairing your subfloor if the damage is minor and the overall structure is sound. However, if you’re facing widespread decay, extensive water damage, persistent sagging, or significant rot, it’s essential to replace the subfloor entirely to maintain safety and structural support. While minor repairs cost less than replacing your subfloor, substantial damage requires a full replacement for lasting results.

A flooring professional can replace only the damaged section of your subfloor when the remainder of the structure is still solid. They remove the compromised portion with precise cutting tools and install an exact match to restore integrity. 

This section-by-section replacement conserves resources, minimizes disruption, and maintains the overall strength of your flooring while ensuring that any necessary reinforcement is completed when needed.

Replacing a subfloor takes a defined amount of time that depends on the project’s scope and the installer’s expertise. Minor sections of damaged subfloor are replaced within a few hours, whereas complete subfloor replacement for an entire room takes several days when factoring in removal, underlying repairs, and new installation. Each phase—preparation, removal, repair, and installation—is carried out meticulously to ensure a safe and durable result.