What We Found Behind the Siding: Why Weather Barrier and Flashing Matter When You Replace Windows and Siding
When we tore the old siding off this home, we expected to find house wrap and flashing around the windows. Instead we found nothing. There was no weather barrier and no flashing, just bare sheathing and a window opening with no protection against water.
Before any new house wrap went up, our crew flashed that window. The video above shows what we did and why. Most homeowners never see these layers, but they decide how long your home stays dry.
Siding Isn't Waterproof
Many people think siding is what keeps water out of their walls. It's actually only the first line of defense. The Vinyl Siding Institute says vinyl siding is an exterior covering, not a water barrier. It's built to let the wall behind it breathe, so it is not watertight.
Wind-driven rain, melting snow and splash-back will get behind any siding. What happens to that water next depends on the layers underneath.
The Weather Barrier: Your Home's Raincoat
A weather-resistive barrier, often called house wrap, is a continuous layer over your wall sheathing. Water that gets past the siding hits this layer and drains down and out, instead of soaking into the wood.
For it to work:
It has to cover the wall continuously, with no gaps or tears.
Seams have to overlap like shingles, upper layers over lower ones, so water always flows outward.
It has to tie into the flashing at every window, door and penetration.
Windows Are the Weak Spots
Building experts often cite a "10/90 rule": about 90% of water problems start in just 1% of a home's exterior. That 1% is mostly the openings, like windows, doors and roof-to-wall joints.
Window flashing is a waterproof membrane or tape around the window opening. It's layered so water running down the wall gets steered past the window instead of into the rough opening. Caulk alone isn't enough. Sealants shrink and crack in the sun, and once they fail, water goes right in.
What Happens When These Layers Are Missing
Water that gets into a wall can't dry out easily. Once wood stays wet long enough, rot and mold can start, often with nothing visible from outside or inside until there's real damage. Swollen or soft sheathing, stained drywall, peeling paint around windows and musty smells are common late warning signs.
Why Utah Homes Need Extra Care
Our weather is hard on walls. Snow piles up against the house and melts slowly, soaking the lower wall for days. Freeze-thaw cycles push trapped water deeper into joints and small gaps. On top of that, homes built under older building codes (before about 2006) often weren't required to have a weather barrier behind the siding. That's exactly what we found on this house.
Why Replacement Is the Right Time to Fix It
Siding and window replacement is the one time those hidden layers are fully exposed. Once new siding goes on, they're covered for decades. If a contractor skips the barrier or puts new windows into openings that aren't flashed, the problem is just sealed in behind beautiful new materials.
At Comfort Home Improvement, our standard on every job is:
Inspect the sheathing and openings once the old siding comes off.
Repair damaged or soft sheathing before anything goes over it.
Flash every window and door opening so water drains out, not in.
Wrap the home in a continuous, properly lapped weather barrier.
Integrate the flashing and wrap so every layer sheds water down and away.
None of this is the part you'll see when the job is done. It's the part that protects your home for the next 30 years.
Get Your Free Quote
Thinking about new windows or siding? We'll look at more than the surface and tell you what's really going on behind your walls. Book a time that works for you and we'll come take a look.
Prefer to talk? Call or text 801-656-7524
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