Soft Spots on Your Floor: A Water Damage Red Flag

Soft spots usually come from a slow leak, not a sudden flood. A dripping supply line under a sink, a failing toilet seal, or a leaking dishwasher can soak the subfloor for weeks before you notice. Winter thaw and summer humidity can also push moisture through cracks in the foundation or slab.

When water seeps into plywood or oriented strand board, the wood fibers swell and lose their rigidity. Over time, the material rots, and the floor above it starts to flex. The soft spot might feel spongy, or it might crack and sag when you walk across it. The longer the moisture sits, the more structural damage it causes.

Before you tear up any flooring, locate the leak. Turn off the water supply to obvious fixtures like toilets and sinks, then watch the soft spot for a few days. If the area stops growing, the leak is likely in that fixture. If it keeps spreading, the source may be a supply line inside a wall or a roof leak.

For roof leaks, check the attic for wet insulation or stains on the rafters. For slab leaks, feel for warm spots on the floor, which can indicate a hot water pipe. Freezing winter temperatures can also burst pipes, so check for ice or frost in exposed lines.

Once the floor is repaired, take steps to avoid a repeat. Fix any plumbing leaks right away, and check under sinks and around toilets every few months. In winter, keep your home at a steady temperature to prevent pipes from freezing, and know where your main shutoff valve is so you can stop a leak fast.

Use a dehumidifier in damp basements or crawlspaces, and make sure gutters and downspouts direct water away from your foundation. If you have a slab, seal any cracks you find. Regular checks are cheaper than a full floor replacement later.

• Fix plumbing leaks promptly
• Check under sinks and toilets monthly
• Know your main shutoff valve location
• Run a dehumidifier in damp areas
• Seal foundation cracks
• Keep gutters clear