How to Fix Leaky Siding

Leaky siding can cause significant water damage in your home, leading to mold growth, wood rot, and compromised structural integrity. Fortunately, many siding leaks can be fixed relatively easily with the right approach and materials. In this video and guide, This Old House general contractor Tom Silva shows where common siding leaks occur and how to repair them quickly. 

How To Find Siding Leaks

Siding leaks often develop slowly and go unnoticed until more severe problems arise. Early detection and repair are crucial to preventing further damage to your home’s structure, insulation, and interior walls. Here’s a more detailed guide to help you thoroughly inspect your siding for leaks and address any issues you find.

Check for Water Stains on Interior Walls and Ceilings

Water stains on your home’s interior walls or ceilings are often one of the first signs of a siding leak. These stains usually appear as discolored patches, often yellowish or brown, and can indicate that water has breached the exterior siding and penetrated the walls. To check for these signs:

• Look for discoloration: Inspect the walls and ceilings, particularly near exterior walls, corners, and around windows and doors. Any discoloration or watermarks may indicate a leak.
• Check for peeling paint or wallpaper: Moisture can cause paint to bubble or peel, and wallpaper may start to lift or wrinkle. This is another potential sign of water intrusion from faulty siding.
• Investigate damp or soft spots: Press lightly on suspicious areas. Soft or damp drywall suggests that water has been infiltrating the walls for some time, potentially causing further damage to insulation and framing behind the siding.

Examine the Exterior Siding for Visible Damage or Gaps

Once you have checked for interior signs of water damage, it’s time to inspect the exterior siding for potential sources of leaks. Common types of damage include cracked, warped, or missing siding panels. Pay close attention to:

• Cracks and splits: Look for any visible cracks or splits in the siding, especially in areas that receive direct sunlight, as UV rays can weaken materials over time. Even small cracks can allow water to seep behind the siding and into the wall.
• Warped or loose siding: Warped or loose siding panels can create gaps where water can enter. This issue is common with wood and vinyl siding. Check to ensure all siding is properly fastened and lies flat against the house.
• Missing panels or shingles: Strong winds or storm damage can result in missing siding panels or shingles. These missing pieces leave your home vulnerable to water intrusion and should be replaced promptly.
• Caulking issues: Check around seams and joints where siding panels meet, as well as where the siding meets trim. Deteriorated or missing caulk can create gaps that allow water to enter.

Inspect Areas Around Windows, Doors, and Other Openings

Windows, doors, and other openings such as vents and electrical outlets are common entry points for water due to the breaks in the siding material. Improper installation or worn-out seals in these areas can lead to leaks. During your inspection:

• Check caulking and seals: Carefully inspect the caulking and weatherstripping around windows and doors. Cracked or deteriorating caulking can create openings where water can get in. Ensure seals are intact and replace or repair any damaged areas.
• Look for gaps around openings: Gaps between the siding and window or door frames can allow water to seep inside. Use a flashlight to closely examine these areas, especially around the top and sides of windows and doors, where water is most likely to enter.
• Check flashing: Flashing is the material that diverts water away from openings like windows, doors, and chimneys. Damaged or improperly installed flashing can lead to leaks. Inspect these areas carefully and ensure that the flashing is in good condition.

Look for Signs of Water Pooling or Drainage Issues

Even if your siding appears intact, poor drainage around your home can cause water to pool against the foundation or lower sections of the siding, eventually leading to leaks. Here’s how to assess drainage issues:

• Inspect the ground around your home: Look for areas where water pools after rain. Water that accumulates near the foundation or exterior walls can eventually seep behind the siding, causing leaks and foundation damage.
• Check gutters and downspouts: Ensure that your gutters and downspouts are functioning correctly and are free of debris. Clogged or improperly directed downspouts can cause water to overflow and run down the exterior walls, leading to potential siding leaks.
• Examine your landscaping: Sloping soil or mulch away from your home helps direct water away from the foundation. If your landscaping slopes toward your home, water may collect against the siding, contributing to leaks over time. Regrade the soil if necessary to ensure proper drainage.

Choosing the Right Materials for Siding Repairs

The type of materials used in your siding repairs can significantly affect their longevity and effectiveness. Below, we will outline the common supplies and materials.

Caulk and Sealants

Select a high-quality exterior product that is specially designed for your siding material, whether it is wood, vinyl, or fiber cement. The caulk or sealant should be flexible enough to accommodate the natural expansion and contraction of your home’s exterior, which can help prevent future cracking and leaks. If you intend to paint over the repaired area, choose a paintable sealant to create a smooth finish that matches the rest of your siding.

Replacement Siding

Remember to choose replacement siding material and style that matches your existing siding. This will help the repaired area blend in with the rest of your home’s exterior. If you’re replacing large sections of siding, you might want to consider upgrading to more durable or low-maintenance materials. Newer options can provide better protection against the elements and reduce the need for future repairs, ultimately saving you time and effort in the long run.

Tools

You’ll need a caulk gun for precise application of sealants, helping you achieve a clean and even seal that will last. A pry bar or zip tool can help you remove damaged siding pieces and detach the old siding carefully without damaging the surrounding material. Lastly, tin snips or a utility knife will help you cut replacement siding to the correct size.

Fixing Leaks Around Windows

Windows are a common area for siding leaks due to the intersection of different materials and the potential for gaps. Below are the steps to check and repair your windows. 

Check Window Condition

Before sealing any gaps, make sure the window itself is in good condition. Poor window condition can negate any repairs made to the siding:

1. Inspect the windowsill for rot or damage
2. Check that the storm window is properly installed
3. Verify that weep holes are present and unobstructed

Seal Gaps with Caulk

Follow these steps to repair any gaps:

1. Clean the area thoroughly and allow it to dry completely
2. Use a high-quality silicone or tri-polymer sealant
3. Apply caulk along the vertical seams between the J-channel and window casing
4. Seal any visible gaps between the siding and window frame

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Newborn Caulking Gun

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Prices taken at time of publishing.

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Addressing Other Common Siding Leak Issues

While window areas are common sources of leaks, siding leaks can also occur in other locations. Use these recommended repair tips to address various siding leak issues.

Repair Damaged Siding

If your siding has cracks, holes, or other damage, repair it promptly to prevent further deterioration:

1. Remove the damaged section of siding
2. Repair or replace the underlying water barrier if necessary
3. Install a new piece of siding, verifying proper overlap and secure attachment
4. Seal any joints or seams with appropriate caulking

Fix Loose or Gapped Siding

Use the following steps for siding that have become loose or developed gaps:

1. Gently lift the loose section of siding
2. Check for and repair any damage to the underlying structure
3. Reattach the siding securely, using additional nails if needed
4. Apply a bead of caulk along the top edge of the siding to prevent water entry

Address Flashing Issues

Here is a step-by-step process for repairing improperly installed or damaged flashing:

1. Inspect flashing around windows, doors, and roof-wall intersections
2. Remove and replace any damaged or corroded flashing
3. Make sure there is proper overlap and slope for effective water drainage
4. Seal the edges of the flashing with appropriate caulking or sealant

When to Call a Professional for Siding Repair

Although most capable homeowners can manage basic siding repair, professional help may be necessary for extensive damage. If you encounter any of these challenges, we suggest seeking advice from a qualified siding contractor:

• Complex flashing or waterproofing requirements
• Extensive water damage or mold growth behind the siding
• Large-scale siding replacement or upgrades
• Structural issues affecting the integrity of your home’s exterior

Siding Maintenance Tips

To maintain your repaired siding, conduct annual inspections, paying close attention to joints, seams, and areas around openings. Clean your siding regularly to remove dirt and debris that can trap moisture. Verify proper drainage around your home’s foundation to prevent water from seeping behind the siding, and trim trees and bushes away from your home to prevent damage from branches.