Bathroom Subfloor Repair: Federal Way Residents’ Guide to Ensuring a Watertight, Solid Floor

Have you ever wondered how your bathroom subfloor is doing? The actual floor under the tilework can certainly take a lot of beating. The toll taken by daily use is usually inconsequential, but when moisture comes into play, it’s time to worry. Water damage is a real problem in Federal Way’s damp climate, and learning how to patch your subfloor can mean the difference between a minor fix and an expensive structural repair.

That all said, here are some tips and tricks for bathroom subfloor repair Federal Way homeowners should keep in mind. Note that these are intended for minor water damage, and you may need to get help from the professionals for the more serious cases.  

How Do I Know If My Bathroom Subfloor Is Bad?

Before you start thinking about doing repairs, it is important to know whether or not there is indeed water damage in your bathroom subfloor. You will need to look out for the following signs: 

• Soft spots. When your bathroom has water damage, the most tell-tale sign is soft, spongy areas in the floor, especially near the toilet and the wet areas. 
• Loose, cracking, or warped flooring. Water damage can weaken and sag the subfloor, resulting in significant damage to the finish. Tiles may crack or become loose, while vinyl laminates may warp as the underlying moisture may weaken their bond with the subfloor. 
• Discolored grout. Moisture in your subfloor promotes mold growth that may discolor the grout in between your tiles.
• Loose toilet base. Unstable, rocking toilets usually indicate that the subfloor beneath them has rotted and may need repairs.
• Ceiling stains. In upper-level bathrooms, the most telling sign of water damage is water stains on the ceiling below. Excess moisture in the subfloor, with gravity’s help, will inevitably find its way to the lower layers.

These signs should also indicate the extent of the water damage in your subfloor. The gist is that if the rot is already affecting your bathroom’s structure or seeping into other areas of your house, skip the DIY and call a professional bathroom repair contractor. 

Can a Water-Damaged Subfloor Be Repaired?

Yes, it is possible to repair a water-damaged subfloor. In fact, this is an urgent matter, as water-induced rot can make your floor unstable and your bathroom unsafe to use. Let’s take a look at two ways to fix water-damaged subfloors. 

Option A: Going DIY For Minor Water Damage

Let’s start with a proven three-phase method for DIY bathroom subfloor repair Federal Way homeowners should follow. Note that this process is only applicable to surface-level damage that affects small, localized spots, typically within a 3-foot radius. 

Phase 1: Preparation and Assessment

This phase involves investigating and preparing the water-damaged parts of the subfloor for removal and repair. Here are the three crucial preparatory steps:

1. Stop the leak. Find and fix the source of water that’s causing the damage. Do not proceed any further until you’ve taken care of the issue, or you’ll risk recurring water damage to your subfloor. 
2. Remove the existing flooring. Carefully remove the layer on top of and around the water-damaged spot. If the damage is near the toilet or baseboards, you have to take these out as well.
3. Assess the damage. Probe the exposed subfloor with a hard tool like an awl or screwdriver. Remove any wood that is significantly discolored or is crumbly, soft, or spongy to the touch. Be sure to also check the joists and cut out any water-damaged sections. 

Phase 2: Damaged Subfloor Removal

The water-damaged parts of the subfloor need to be removed; there’s no point in keeping compromised wood. You’ll need a pencil, a saw, and cleaning equipment at this stage. When ready, follow these steps:

1. Mark the area to cut. Draw a rectangle that covers the damaged area of the subfloor. Make sure that the lines run over the center of the nearest joist or floor support. 
2. Cut out the damaged subfloor. Use a circular saw with adjustable depth and bevel settings for this task. Set the blade to the same thickness as your subfloor boards to avoid cutting on the joists. 
3. Clean up. Use a vacuum cleaner to clear the area of the debris from the previous step. You don’t want to continue working amidst fine sawdust and possible mold spores. 
4. Check the joists. Assess the exposed joists for damage. If they show any sign of water damage, saw off the damaged parts and repair them by sistering the joints with new wood shaped to fit into the gap.
5. Dry the area. Run a fan or dehumidifier for a few days to dry the workspace. Make sure that the subfloor and affected joists are completely dry before you start installing a new subfloor. Adding dry wood to a wet framework risks the recurrence of water damage and mold growth. 

Phase 3. New Subfloor Installation

At this point, you should be ready to replace the damaged subfloor with new wood. This part is relatively straightforward, and here’s what you need to do:

1. Prepare your materials. Find wood of the same thickness as your subfloor. Additionally, have a wood adhesive and a power tool on the ready. 
2. Cut the patch. Measure the hole you’ve cut out of your subfloor, and cut a new piece close to the same size. It should have a ⅛” gap in the sides to accommodate expansion due to changes in temperature. 
3. Secure the patch. Apply the adhesive to the exposed joints, then gently press the patch into place. Secure the piece by drilling deck screws every 6” to 8” along the perimeter, right on top of the joists and supporting structure.
4. Finish the surface. Use a leveling compound to smooth out the floor in case of any height difference between the patch and the surrounding subfloor. As soon as the compound has set, you may now install your tiles or vinyl flooring. 

Option B: Getting Help From a Contractor

Regardless of the extent of the water damage, it is still highly recommended that you hire a bathroom remodel contractor to address the issue. They can spot damage that the untrained eye might miss, and have the right tools and skills to implement a long-term fix. However, be sure that you only work with a reliable contractor with a proven track record to get your money’s worth. 

How Much Does It Cost to Replace a Subfloor In a Bathroom?

For bathroom subfloor repair, Federal Way residents typically pay contractors between $900 and $3,000. That would be $1,560 on average, with the actual amount depending on the severity of the subfloor damage.

Conclusion

Subfloor damage, especially that caused by moisture buildup, should not be taken lightly. After all, the subfloor practically keeps your bathroom floor together. Given Federal Way’s typically humid climate, doing nothing will only worsen the damage, compromising your home’s safety.