How to Fix Leaky Siding

A side of a house with wood siding.
  • 4-12 hours
  • Beginner
  • 25-100

Are ugly stains showing up on the interior walls or exterior siding of your home? Discoloration or warped paint and wallpaper are often signs that water has trickled in where it doesn't belong. In many cases, the stain's location will help you determine where the problem is coming from, but sometimes it's not that obvious. If you've ruled out breaches in your roof and plumbing system, you may have a problem with leaky siding.

If you believe this is your problem, you'll need to know the proper way to repair the issue in order to prevent further damage. Depending on the type of siding you have, wood or vinyl, you will have to take a specific approach in fixing the problem.

Repairing Leaky Wood Siding

Step 1 - Examining your home's exterior structure is the first step toward finding your leaky siding area. Start by looking in the area where you’ve spotted the stain. Go to the same spot on the exterior portion of the wall and look around. Water could be seeping in from above the discolored area, so be sure to grab a ladder and really examine the wall.

Even if you don’t see stains on your outside wall, it's important to check for other signs of leaky siding and water damage. If the wood is cracked or loose, this may be where the water is coming in. If the crack is no more than 1/2 inch wide, you can repair it. If it's larger than 1/2 inch wide or it's compromising the board, you should replace the entire segment.

Step 2 - Once you’ve found the compromised area and determined it can be repaired rather than replaced, you need to prepare the wood by cleaning out any rot, sanding it down, and wiping off debris. You can then apply your product to the surface.

To repair leaky siding you can use exterior caulk to fill in any small cracks. O

To repair leaky siding you can use exterior caulk to fill in any small cracks. Once it has dried, you can paint over it to maintain your home’s curb appeal.

If the crack is too large for caulk repair, you can use a wood filler or putty to fill in the area. You'll want something strong like Bondo or Quickwood. These products are usually mixed with another chemical that causes them to harden when dry. (Tip: These solutions are designed to quickly dry and harden, so you have to be quick and effective when working with them.)

Step 3 - Once the crack is completely filled in, you need to wait for it to dry. Don't worry about the messy application, as your next step is to sand down the excess product with 80-100 grit sandpaper.

Note: For leaky siding that needs to be completely replaced due to irreparable damage or mold growth, you can find the replacement boards at a local lumber store. Before you go, make sure to measure the board width and length, and take pictures so that your local lumber representative can help identify the correct replacement.

Windows and Doors

If you weren’t able to locate damaged or loose planks on the exterior wall, your interior water damage could be coming from a nearby window or door. A drip around a door or window with natural wood materials often means you have an issue with loose or missing caulking.

Inspect your window or door frame caulking. If it appears to need reapplication,

Inspect your window or door frame caulking. If it appears to need reapplication, remove the old caulking with a remover tool and apply new weatherized caulking around the frame.

Repairing Leaky Vinyl Siding

Believe it or not, vinyl siding is the most common type of siding to have water or moisture problems. As much as it seems that vinyl would be better than most other types at moisture prevention, it's actually not. Since it needs to be able to flex and move in hot and cold temperatures, vinyl siding is loosely attached to a house and there's a lot of room for blowing rain to enter right underneath.

Windows and Doors

The most troublesome areas for the installation of vinyl siding are around doors and windows, and of course anywhere that it will be butting up against or seaming to another piece of siding or the home. If your trouble area is in one of these areas, you'll need to check for a few things.

Step 1 - First, check around the window where the siding is capped off with a trim piece. Make sure that this piece has been correctly attached to the home. It should move and flex, but it shouldn't be completely free for movement, meaning that it shouldn't completely move away from the home if you pull at it. If there are gaps and water can get in, you can use tri-polymer caulking to fill it in. This is a caulking that's flexible and works well with vinyl siding. Caulk along the seams of the siding where it meets the window.

Step 2 - You can also check above the window or door to see how the siding is attached there. If it was installed properly, there shouldn't be any water running behind the siding and causing issues. There may, however, be some improper attachment of the flashing or the J-channels. For this, you should have a reputable contractor come out and either pay for their advice or have them do the job properly.

Other Leaky Areas

Leaks in other areas of the home besides windows and doors are not as common as they may be for homes with wood siding, but they still may happen. If you do find such an area, remove the siding and inspect the walls behind it to determine how the water is getting in. There is usually going to be some sort of seam or area where it has been joined together.

If the area has no seam, it may be that you live in an area that gets a lot of wind and rain and that the water is blown up under the siding and into your home. With an insulation or weather barrier, however, there shouldn't be a leaking issue, at least not unless the home and barrier are quite old.

Are ugly stains showing up on the interior walls or exterior siding of your home

This is a good time to ensure that the home is in fact protected by a weather barrier because if you find no other issue for a leak, such as water running down the siding from blocked gutters or windows that are not properly sealed in, then the barrier is either not there or not doing its job anymore and needs to be added or replaced.

No matter what type of siding you have, if you do not have a weather barrier or insulation over your plywood exterior and under the siding, you're going to have multiple leaking issues. Although it will be an expense to remove your vinyl siding and put up a weather barrier now, if you wait for the future to repair as things come up, you'll be spending more money later because the plywood base of the home's walls may possibly need replacing, and not just the siding.