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Red Stag Windows & Doors logoRed StagWindows · Doors · LA
Weatherproofing & Sealing

Window & Door Weatherproofing Los Angeles

Same-day finish. No tarps overnight. The detail that decides if a window job lasts 10 years or 40.

$800+
Project range starts
Half-day
Typical finish
Lifetime
Workmanship warranty
Photographed
Every opening at install
Why weatherproofing fails first

The cheapest line item, the most common point of failure.

Caulk lasts 8 years. Properly detailed liquid-applied flashing lasts 30+. Most LA leak calls trace back to that gap.

When a window starts leaking five years after install, it's almost never the window. It's the seal between the window and the wall — and nine times out of ten, that seal was a bead of exterior caulk doing a job a real flashing system was supposed to do. Caulk shrinks. Stucco moves. UV breaks the bond. By year eight, there's a hairline gap behind the trim that funnels every winter storm straight into the framing.

The water doesn't show up on your wall. It runs down the back of the sheathing, soaks the bottom plate, and rots the rough sill from the inside. By the time paint bubbles in the living room, you've already lost the framing under that window. We've opened up enough rotted sills in Mar Vista, Highland Park, and Eagle Rock to know the pattern: the original installer caulked over the weep holes, skipped the sill pan, and the homeowner never knew until the drywall started staining.

Proper weatherproofing is layered: liquid-applied flashing (Prosoco R-Guard) at the rough opening, butyl tape (Grace Vycor Plus) at the sill, backer rod and a polyurethane sealant (Sika or Tremco) at the perimeter joint, and only then a finish bead of exterior-grade caulk on top. Each layer assumes the one above it will fail eventually. That's the spec. That's why it lasts.

Pricing breakdown

Three tiers. Real numbers.

Standalone refresh on existing windows, or rolled into an install. All-in pricing — labor, materials, disposal.

Caulk + sealant refresh
$60–$90
Newer windows, intact flashing, surface-level fade
  • Cut out failed exterior caulk
  • Clean and prime the joint
  • Backer rod where joint exceeds 3/8"
  • Sika or Tremco polyurethane bead
  • Per-window pricing — door units $150–$220
Tape + flashing repair
$90–$140
10–20 year old installs, visible water staining
  • Pull exterior trim, inspect rough opening
  • Replace failed butyl tape at sill
  • Spot-apply Prosoco R-Guard at gaps
  • Re-set trim, full perimeter rebuild
  • Door units $220–$350
Full weatherproofing rebuild
$140–$350
Active leaks, 25+ year installs, pre-stucco-repair prep
  • Strip existing trim to rough opening
  • Full liquid-applied flashing (R-Guard)
  • New Vycor Plus sill pan + jamb tape
  • Backer rod, sealant, new trim, paint-ready finish
  • Photographed at every layer
What's included

Every weatherproofing job, every contract.

Refresh vs rebuild

When a $90 caulk refresh is enough — and when it isn't.

If your windows are under ten years old, the original install was done right, and you're seeing hairline cracks in the exterior caulk on the south or west elevation, that's a refresh job. Cut out the old bead, prime, backer rod where needed, run a new sealant line. Half a day, no surprises, and you buy another decade.

If you're seeing any of these — moisture stains on interior drywall below a window, soft trim wood when you push on it, paint bubbling on the exterior sill, dark streaks down stucco below a window head — caulk won't fix the problem. The water is already past the surface. A full rebuild pulls the trim back to the rough opening, dries out the framing (or replaces it if rot is structural), and re-flashes the whole assembly with R-Guard and Vycor.

The middle case — windows 12 to 20 years old, no visible leaks but original install quality unknown — is the call we make on-site. We pull a corner of trim, inspect the original flashing, and tell you straight: refresh holds, or it doesn't. About 40% of mid-age homes we open up need at least a partial rebuild.

What other contractors miss

Six weatherproofing fail modes we see weekly.

Every one of these has shown up on a leak inspection in the last 90 days. Every one is avoidable at install.

Five steps · zero surprises

From inspection to sealed. In writing.

Standalone weatherproofing jobs run a single visit. Every step is photographed and signed off.

01
Day 1
Consult
Free 30-min walkthrough. We probe trim, check for soft framing, and tell you refresh-vs-rebuild on the spot.
02
Day 1
Inspect
Moisture meter readings logged at every opening. Hidden rot flagged before the contract.
03
Week 1
Order
R-Guard, Vycor, Sika, backer rod sized to the joints we measured. Nothing substituted day-of.
04
Week 2
Install
Half-day to one day on most homes. Photographed at every layer. Same-day finish, no tarps.
05
Week 2
Inspect
Final walkthrough with the homeowner. Photo log emailed. Lifetime workmanship warranty issued.
Real jobs

What customers wrote afterward.

★★★★★

"Had a leak above the kitchen window every January for three winters. Two contractors caulked it and it came back. Red Stag pulled the trim, found rotted sheathing under the sill, and rebuilt the whole opening with R-Guard. Two winters dry now."

L
Lauren V. — Mar Vista
Google · Single-window leak fix
★★★★★

"Bought a 1962 ranch in Eagle Rock. The inspection flagged 'aging exterior caulk' on every window. Got three quotes — Red Stag was the only one who actually opened a corner before bidding. Turns out half needed full rebuild, half were fine. They priced each one separately. Saved us about $4,000."

B
Ben S. — Eagle Rock
Yelp · 11-window assessment
★★★★★

"Theo found rot behind the master bedroom window I didn't know about. The original installer had caulked the weep holes shut in 2009. We replaced framing on two openings, re-flashed everything. Photo log is the most thorough documentation I've ever gotten from a contractor."

P
Priya M. — Highland Park
Houzz · Weatherproofing rebuild
Honest answers

What every homeowner asks first.

01Can you fix leaks without replacing the window?
Most of the time, yes. About 70% of window leaks we see are weatherproofing failures, not window failures — bad flashing, blocked weeps, or failed perimeter sealant. We diagnose first. If the window itself is sound (glass seal intact, sash operates, frame square), we rebuild the seal around it for a fraction of replacement cost.
02How do I know if my caulk has failed?
Run a fingernail along the exterior bead. If it's chalky, cracked, or pulls away from the frame, it's done. Other tells: hairline gaps you can see daylight through, dark staining on stucco below the window, or any soft spot in the trim wood. If the windows are 10+ years old and the caulk has never been touched, assume it's at end-of-life.
03Is this covered under my window warranty?
Almost never. Manufacturer warranties (Andersen, Marvin, Milgard, Anlin) cover the window unit — glass seal, sash, hardware. They explicitly exclude installation flashing and exterior sealant, which are the installer's responsibility. That's why our lifetime workmanship warranty matters.
04Same-day finish — really?
Yes. Standalone refresh jobs (cut, clean, re-bead) run 4–6 hours for a typical home. Full rebuild on a single opening is one full day. Multi-opening rebuilds we phase by elevation so no opening is ever left tarped overnight.
05Do you photograph the work?
Every layer. Sill pan, jamb tape, liquid-applied membrane, backer rod, sealant. Date-stamped, filed with your warranty paperwork, emailed within 48 hours of completion. If a future leak ever happens, we (or the next homeowner) know exactly what's behind the trim.
06What sealant do you use?
Sika or Tremco polyurethane for the structural perimeter joint — they flex 25%+ through joint movement and bond to stucco, vinyl, fiberglass, and clad wood. Prosoco R-Guard FastFlash for liquid-applied flashing. Grace Vycor Plus for butyl sill tape. We don't use silicone on weatherproofing joints — paint won't bond to it and it can't be re-sealed without full removal.
07How long does liquid-applied flashing last?
Manufacturer-rated at 30+ years behind cladding. R-Guard cures to a continuous rubberized membrane with no laps or pinholes — that's the durability advantage over taped flashing alone. We've opened up R-Guard installs from 2014 that still test at full performance.
08What about stucco cracks around my windows?
Hairline stucco cracks at window corners are normal in LA — diagonal cracks from the corners of openings are how stucco relieves seismic and thermal stress. They don't leak through the stucco itself, but if water tracks down the crack and finds a gap in the perimeter seal underneath, that's how it gets in. We seal the joint behind the stucco; a stucco contractor can patch the visible crack separately.
09How do I know if my windows need weatherproofing vs full replacement?
If the window frames are structurally sound and the glass seals are intact (no foggy double-panes), weatherproofing can extend window life by 5–10 years at a fraction of replacement cost. If the frames are warped, the rough opening shows rot, or the glass seals are failed, replacement is the more cost-effective path — patching a window that needs replacement adds cost without extending life.
010What's the difference between weatherstripping and weatherproofing?
Weatherstripping is the compressible seal between the sash and frame (the strips on the moving parts). Weatherproofing in our context refers to the perimeter sealing between the window unit and the surrounding wall — the caulk, flashing, and drainage details at the frame-to-stucco or frame-to-wood-siding interface. Both matter; they address different infiltration paths.
Service area

Weatherproofing across Los Angeles.

Same crew, same trucks, same 45-minute drive if a joint lets go in 2031.

Weatherproofing in the LA climate

Why LA homes need weatherproofing — and what's different about sealing here vs other climates.

LA's mild climate creates a specific weatherproofing problem that's counterintuitive: because it rarely rains hard and for sustained periods, moisture infiltration when it does rain is catastrophic to buildings that weren't designed for it. A New England home is built to drain and dry repeatedly over decades. A 1950s LA stucco-and-wood-frame home was built assuming modest weather exposure — and in the wet years (2023, 2024) it shows.

Where LA homes fail weatherproofing. The failure points are predictable: window and door perimeter caulking that's been painted over repeatedly and has lost elasticity; sill pan drainage that was never installed or has since clogged; window frame-to-stucco joints that have cracked from thermal movement; deck-to-wall flashing that wasn't detailed for the water volumes of an El Niño year. We see the same failures across thousands of inspections — they're not random.

The sealing scope. A weatherproofing inspection and seal includes: removing existing perimeter caulk to the substrate, assessing whether the substrate is sound, installing backer rod and ASTM C-920 sealant rated for the UV and thermal movement of each joint, and — where existing drainage details are missing or failed — retrofitting a minimal drainage plane at critical transitions. On a typical 1,800 sq ft LA home, a thorough weatherproofing scope runs 1–2 days.

Product selection matters. We use sealant products specified for the substrate and exposure: silicone for glass-to-frame joints (high UV, needs to stay flexible), polyurethane for stucco-to-frame joints (paintable, high adhesion), and butyl for flashing laps where fuel-compatibility with the membrane is required. Using the wrong sealant in the wrong location — a contractor default that's very common — creates adhesion failures that look fine for two years and then open up.

Stop a leak before it rots a wall.

Free inspection. Refresh-vs-rebuild call on the spot. Most jobs finished in a single day, lifetime workmanship warranty included.

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