The short answer
What Causes Siding to Bulge
Moisture is the main reason siding bulges or warps. Water can seep behind the boards through gaps, damaged caulk, or a leaky roof or window. Once trapped, the wood or fiber cement absorbs the water and swells. When it dries, it may not return to its original shape, leaving a permanent bulge.
Another common cause is improper installation with no room for expansion and contraction. In a semi-arid climate with cold winters and hot dry summers, temperature swings make siding expand and contract. If the boards are nailed too tightly or lack proper gaps, they push against each other and warp. Poor ventilation behind the siding can also trap moisture from inside your home.
- Check for gaps in caulk or sealant around windows and doors
- Look for damaged or missing flashing above windows and doors
- Inspect gutters and downspouts for leaks or overflow
- Feel the siding after rain for damp spots
- Look for peeling paint or stains that indicate trapped water
- Check the ground slope near your foundation for water pooling
How to Find the Water Source
Start by inspecting the obvious places: roof edges, window frames, and door trim. Water often enters at these joints. Look for rusted nails, cracked caulk, or gaps where two materials meet. Also check the bottom row of siding, which can wick up moisture from the ground or splash from rain.
If you cannot see a leak, the problem may be inside the wall. A plumbing leak or condensation from the interior can wet the back of the siding. You can use a moisture meter to check the wall from inside. For a thorough search, consider a moisture mapping service to locate hidden damp spots without tearing things apart.
- Use a flashlight to inspect under eaves and soffits
- Check the attic for roof leaks near the walls
- Look for water stains on interior walls that align with the bulge
- Test the siding with a screwdriver for soft or spongy areas
- Review your home's exterior paint for cracks or blisters
What to Do Right Away
If you find a leak, stop the water from entering. That could mean fixing a gutter, sealing a gap, or calling a plumber for a pipe issue. Then, dry the area as soon as possible. Open windows, use fans, or run a dehumidifier to pull moisture out of the wall cavity.
Do not remove the siding yourself if you suspect mold or rot. That can release spores into your home. Instead, contact local water damage pros to assess the situation. They can extract standing water and set up structural drying equipment to dry the wall slowly and prevent further damage.
- Turn off the water supply if you suspect a pipe leak
- Move furniture and belongings away from the affected wall
- Place a bucket under a dripping leak to catch water
- Take photos for your insurance records
- Wear gloves and a mask if you must touch moldy areas
When to Call the Pros
If the bulge is large, the siding is soft, or you see signs of mold, it is time to get help. The pros can locate the exact water source using leak detection equipment. They can also measure moisture levels in the wall to decide if the siding needs to be removed and replaced.
Leaving wet siding can lead to rot, which weakens your home's structure. A water damage inspection can reveal the full extent of the problem. That helps you know what repairs are needed before you spend money on new siding. Acting now can save you from a more expensive repair later.
- If you smell musty odors or see black spots, call a mold professional
- If the bulge is over a window or door, check for a roof leak first
- If you are unsure of the source, a leak detection service can help
- If you have insurance, document the damage and check your policy
How to Prevent Future Warping
Keep your siding in good shape by sealing any gaps and replacing damaged boards promptly. Ensure gutters are clean and downspouts direct water away from the foundation. Also, maintain a small gap between siding boards for expansion, as recommended by the manufacturer.
In a climate with cold winters and hot dry summers, check your siding each spring and fall. Look for cracks, loose nails, or peeling paint. The side of your home that faces the sun and weather may need extra attention. Regular maintenance is the most effective way to avoid bulging.
Water damage does not wait
Water keeps spreading into floors and walls, so it is worth acting early. Calls are answered 24/7.
Call Now (208) 729-2441Frequently asked questions
Can I fix a bulging siding myself?
You can fix a small bulge if you find and stop the water source. Remove the affected board, dry the wall, and replace it with new siding. For large areas or mold, call the pros to avoid health risks.
Will my insurance cover siding damage from water?
Policies vary, and your insurer decides what is covered. Typically, sudden leaks like a burst pipe are covered, but gradual damage from poor maintenance may not be. Check your policy and document everything.
How long does it take for siding to dry after a leak?
Drying time depends on the extent of moisture, the weather, and ventilation. It can take several days to weeks. Using fans and a dehumidifier speeds it up, but the pros can dry the wall cavity more thoroughly.