Siding water damage usually hides until a panel comes off. From the sidewalk, an old wood panel might just look like it needs paint. Behind it, the building paper can be torn, the insulation can be full of debris and the wood at the bottom of the wall can be stained dark from years of water finding its way in.
This post covers why water gets behind siding, what we found when we opened up panels on an apartment building in Ventura, and what a proper repair looks like.
Why water gets behind siding
Siding is not waterproof, and it is not supposed to be. The Building America Solution Center puts it simply: most exterior wall cladding systems leak, and wind pressure and capillary action drive rain through cracks, joints and small gaps. The layer behind the siding is what is supposed to catch that water and let it drain down and out.
When that layer fails, water sits against the wall instead. Common reasons:
- Building paper that is torn, brittle or missing
- Gaps at windows, doors and trim that were never flashed or have lost their seal
- Siding that sits too close to soil or gravel, so the bottom edge stays wet
- Sprinklers hitting the wall every day
- Paint that has worn through, leaving bare wood to soak up water
What we found on an apartment building in Ventura
This job is on an apartment building where sections of the vertical wood siding were marked up on an earlier visit. When the crew pulled the old panels on September 28, the photos show:
- Torn building paper. The black paper behind the siding had holes and tears in it.
- Debris packed at the bottom of the wall. Insulation at the base was mixed with dirt, leaves and snail shells, a sign the bottom of the wall was open to the outside.
- Dark, water stained wood. The sheathing and the wood at the bottom of the wall had dark staining and streaks running down to the base.
How the repair went
- Remove the old panels and the damaged building paper.
- Clean out the wall. Debris and damaged material at the base come out so you can see what is left.
- Check the wood. Stained wood gets probed. If it is soft, it gets replaced. Our termite repair and dry rot page covers what happens when it has gone too far.
- Install a new weather barrier. On this job, new house wrap went on over the wall before any siding went back up.
- Install new siding panels and seal the edges and trim.
- Prime and paint so the new panels match and the wood is protected.
By September 29, new panels were up and the crew was painting them.
Signs you may have water behind your siding
- Paint that peels or blisters on the same panels over and over
- Siding that feels soft, swollen or spongy when you press on it
- Dark staining at the bottom edge of the panels
- Gaps or cracks around window and door trim
- Stains, bubbling paint or a musty smell on the inside of an exterior wall
- Bugs or other critters getting in at the base of the wall
If the inside of the wall is showing it, the water has already made it through. Our post on mold behind drywall covers what can be growing in there.
Why it matters on apartment buildings
On multi unit buildings, one bad section of siding can affect more than one unit, and the repair usually runs through the property manager or the association. Getting the wall opened, documented and closed up properly the first time avoids repeat work and repeat complaints from tenants. Our post on mold in an apartment covers what tenants and owners usually deal with when moisture gets inside.
Simple ways to protect your siding
- Keep a gap at the bottom. Soil, mulch and gravel should sit below the bottom edge of the siding, not against it.
- Aim sprinklers away from the walls. Daily spray on the same panels adds up.
- Repaint before the wood shows. Once paint wears through, bare wood soaks up water every time it rains.
- Check trim and window edges once a year. Recaulk gaps before they open up.
- Keep gutters and downspouts clear so roof water does not sheet down the wall.
FAQ
Can I just caulk and paint the siding?
Paint and caulk help keep water out of the siding itself. They do not fix torn building paper or wet framing behind it. If the panels are soft or keep peeling, the wall needs to be opened.
How long does siding replacement take?
It depends on how much of the wall is involved and what is behind it. On this job, the old panels came off, the wall was wrapped and new panels went up over two days.
Is water behind siding the same as dry rot?
Not always. Water behind siding is the cause. Rot is what happens to wood that stays wet long enough. Catching it early is the difference between a siding job and a framing job.
Seeing signs of water behind your siding?
Total Restoration handles siding repair and water damage restoration in Ventura and across Ventura County, Santa Barbara County and Santa Clarita, for homes and multi unit buildings. Contact us and we will take a look.