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8 Effective Steps for Repairing a Water-Damaged Subfloor

Last Updated on February 10, 2021 by Diana Rodriguez-Zaba

It only takes a minute to wipe up spilled coffee on the kitchen floor. It can take days to recover from water damage after a burst pipe or storm flooding. As you work through the job of cleaning carpets and fixing hardwood floors, you have to be concerned about your home’s subflooring.

Can you dry a subfloor after flooding, or does the entire structure need replacing? How do you deal with a water-damaged subfloor?

Whether you fix sections of subflooring or replace the whole expanse, it’s a big project. It’s also a situation that needs to be addressed as soon as possible.

How to Fix a Water-Damaged Subfloor: Your 8-Step DIY Guide

Subflooring is one of your home’s most important architectural components. It supports the first floor by securing the floor joists that span your basement or crawl space. The subfloor forms an underlying plane that holds up walls and serves as a level foundation for finished floors.

When this structural element gets soaked, you need to start the drying and repair process right away. If you’ve ever handled water damage cleanup on your own, you know how quickly problems can spread.

1. Start by Stopping the Water

Unless you’re dealing with the aftermath of a flood, water in the subfloor has a source somewhere in the house. You need to find it and fix it before starting repairs.

2. Expose the Subflooring

Remove baseboards around affected areas, and pull back carpeting to the nearest wall. If you’re working with vinyl flooring, cut out sections over the water-damaged subfloor, and plan on replacing them after you complete repairs.

Power Tip: As you remove baseboards, inspect adjacent drywall for signs of water damage.

3. Make Your Mark

Use chalk to mark and map areas that need repair. These guides help you make accurate cuts through the damaged subfloor. You want to measure and outline beyond affected areas and close to adjacent floor joists.

Power Tip: There are several ways to locate floor joists, but a stud finder keeps the job easy and accurate.

4. Carefully Cut Subflooring

Put on a pair of work gloves, a dust mask and eye protection. Using a circular saw set to a 1-inch depth, carefully cut out damaged areas by following your chalk mark guides. Cut as closely as possible to floor joists.

5. Remove Damaged Materials

Pull up water-damaged subflooring with a pry bar. Minimize splintering by working slowly. Remove any loose nails, and dispose of everything in heavy-duty trash bags. Use a shop vac to clean up remaining dust and debris.

6. Speed Up the Drying Process

Allow several days for affected areas to dry before finishing repairs. Otherwise, you risk mold growing on damp materials. Several large box fans and a dehumidifier speed up the drying process.

Power Tip: If you find mold in any materials, take care of it before continuing with your subfloor work.

7. Reinforce Floor Joists

Once the entire area is completely dry, reinforce affected floor joists. You can side the joists with 2-inch by 6-inch boards or span spaces with lumber blocking. This step strengthens joists affected by water damage.

8. Install Your New Subflooring

Measure new subflooring material, and cut it to fit. Allow a one-eighth inch gap between old and new subflooring so that the new material can expand. Use deck screws or 8d galvanized nails to fastened down the new subflooring.

Power Tip: Finish the job faster by renting a rapid-load screw gun or nail gun from your home improvement center.

Dealing With Tile Floors

Figuring out how to dry subfloor under tile can be a challenge. Most tile floors adhere to a cement board sandwiched between the floor and subflooring.

You can check for dampness by pulling up tiles, but a restoration contractor takes care of the inspection with special equipment that leaves floors in place. This saves the trouble of removing tiles from a floor that doesn’t need repairs.

When Should I Replace a Subfloor After Water Damage?

subfloor water damage cleanup

Does a wet subfloor need to be replaced? No. If you can begin the drying process immediately after the initial water damage, you may be able to avoid subfloor replacement. It’s best to let restoration professionals address the existing damage. Their assessment gives you an accurate overview of your options.

In cases of extensive water damage, drying the subfloor after a flood can be very difficult, and that complicates repairs. Soaked wood quickly develops mold and rot that impacts adjacent framing and drywall. In this kind of situation, it’s best to replace the entire expanse. Often, homeowners insurance covers subfloor replacement after water damage.

What Causes Subfloors to Get Wet?

An occasional spill isn’t enough to damage a subfloor. However, just one gallon of water can penetrate a floor’s covering and soak the wood structure below. Multiply that small amount by any of these home mishaps and plumbing disasters that cause water-damaged subfloors.

How do I know if My Subfloor is Rotten?

A water-damaged subfloor feels spongy underfoot. It might bounce or squeak when you walk across the room. Sagging boards, damp spots and unpleasant musty smells are also signs of a rotting subfloor.

How Much Does it Cost to Repair a Water-Damaged Subfloor?

Subfloor water damage repair costs depend on the size of the room. Materials are another factor. Most subfloors are plywood, but others are constructed with oriented strand board. You also have to consider how water damage complicates the job.

Dealing with Subfloor Water Damage in the Chicago Area? We Can Help!

We know you can handle most DIY jobs around the house, but we’re always here to help. If you’re concerned about trying to repair or replace water-damaged subflooring by yourself, contact our headquarters in Chicago or Skokie.

Our teams take care of residential water damage repairs and restoration all across the city and suburbs. We can be at your door in less than 45 minutes.

Just give us a call here at ServiceMaster Restoration by Zaba: 773-647-1985