Deck Waterproofing & Flashing in Sammamish, WA
Waterproofing and flashing repair for decks, balconies, windows and roof-to-wall joints. When coatings wear through or flashing is missing at doors and walls, the leak often shows up far from where water gets in. We trace it to the source, replace any wet framing, correct slope and flashing, and finish with a walkable surface that drains away from the house. We serve homeowners across Sammamish and nearby Redmond and Bellevue.
Before
AfterFlashed and rebuilt
Why waterproofing comes up so often in Sammamish
With long rainy seasons and the occasional snow load, Sammamish homes need flashing that does its job at every intersection. Many 1980s and 90s builds were finished with no diverters where roofs meet walls and only thin metal at deck ledgers. Custom homes around Sahalee often have complex rooflines with even more joints. Our work here includes kick-outs, ledger flashing, pans under doors and windows, and peel-and-stick membrane at weak points. Decks or balconies built over rooms get a continuous membrane pitched to drain so water exits the structure cleanly.
Sammamish is largely a 1980s through 2000s city, built out across the plateau above Lake Sammamish. Pine Lake, Klahanie and Beaver Lake neighborhoods are full of large two-story homes with tall walls, steep roofs and big attached decks, usually sided in cedar, hardboard or early fiber cement. Sahalee homes around the golf course tend to be larger and more custom. Along the East Lake Sammamish slope and in Inglewood you find older lake cabins next to newer view homes. Many lots are generous and heavily treed, with decks stepping down toward wooded backyards and greenbelts.
The plateau sits several hundred feet above Lake Sammamish, so Sammamish often gets colder winter nights and more snow than the lowlands nearby. That means more freeze-thaw cycles on decks, stairs and siding. Dense evergreens shade many homes for much of the day, and with long stretches of rain, wood stays damp from fall through spring. Moss grows quickly on roofs and deck boards. On the lake-facing slope, homes also catch wind coming up from the water, which drives rain into west walls.
Our crew comes out from our Woodinville office, and we also work in nearby Redmond, Bellevue, Woodinville and Kirkland.
When to call about waterproofing in Sammamish
- Streaks down the wall below a roof edge
- Rot or stains under windows and doors
- A deck that slopes toward the house
- Stains or drips on the ceiling below a deck or balcony
- Water pooling against the house after rain
Our waterproofing process, step by step
Trace the leak
Moisture readings, inspection openings and photos to find the real source.
Repair the substrate
Rotted plywood, joists or sheathing are replaced before sealing.
Correct slope and details
Proper slope, sill pans and flashing at every edge and door.
Apply the system
Primer, membrane and walkable top coat applied in layers.
Water test
We test the problem areas and show you the finished details.
Recent waterproofing projects near Sammamish
What we do in Sammamish
Walkable deck coatings
Waterproof coating systems for decks and balconies over living space.
Window head flashing
Flashing and tape around windows to stop leaks into the wall.
Leak investigation
We trace leaks to the source before anything is sealed.
Kick-out flashing
Diverts roof water away from the wall at roof-to-wall joints.
Door and sill pans
Pan flashing under doors, where many balcony leaks start.
Slope correction
Fix flat or back-sloped decks so water drains away from the wall.
Neighborhoods and permits in Sammamish
Pine Lake and Beaver Lake homes sit under thick tree cover, so fascia, deck boards and north walls take most of the damage. Klahanie’s 1980s and 90s homes often have hardboard siding nearing the end of its life. Around Sahalee, larger custom homes have more complex rooflines and more flashing joints to fail. On the East Lake Sammamish slope, view decks and west walls get direct wind and rain off the lake.
Minor matching repairs to boards or trim are usually handled without paperwork. Bigger decks, framing work and whole-wall siding jobs tend to need approval first. We reach out to the City of Sammamish during the estimate stage, so you know what to expect, and our team handles applications and inspection visits if a permit applies.
Deck and balcony surface options
| System | Best for | Expected life | Maintenance |
|---|---|---|---|
| Recoat existing membrane | Sound surface with a worn top coat | A few years per top coat | Keep drains clear, recoat when worn |
| New walkable membrane | Decks and balconies over living space | 10–15+ years | Top coat every few years |
| Membrane under decking | Dry space under a deck with a wood or composite surface | 15+ years | Keep gaps and drains clear |
| Rebuild, slope and membrane | Wet or rotted plywood, flat or back-sloped deck | 15+ years | Top coat every few years |
What waterproofing typically costs in Sammamish
| Project | Typical scope | Price range | Timeline |
|---|---|---|---|
| Flashing repair | Kick-out, head flashing or a door pan at one spot | $600 – $2,500 | 1 day |
| Recoat a balcony | Prep and top coat over a sound membrane | $1,500 – $4,500 | 2–3 days |
| New walkable membrane | Full membrane system on a deck or balcony | $5,000 – $14,000 | 4–7 days |
| Rebuild and waterproof | New plywood, slope correction, flashing and membrane | $12,000 – $30,000+ | 1–3 weeks |
These are typical 2026 ranges we see for waterproofing in Sammamish and nearby cities. Your price depends on what we find once the area is open, access and height, and the materials you choose. Every estimate is free, in writing and based on an on-site inspection with photos.
Waterproofing in Sammamish: cost and timing
Most common causes
Worn deck coatings
Coatings wear through first at doors, edges and posts, and water reaches the plywood underneath.
Doors without sill pans
Water that gets under a threshold runs into the subfloor and the room below.
Missing kick-out flashing
Roof water runs down the wall instead of into the gutter and soaks the siding and framing.
What drives the price in Sammamish
Waterproofing in Sammamish depends on the size of the deck or balcony, how much substrate has to be replaced, slope correction and how many doors and walls need new flashing. Recoating a sound surface costs far less than rebuilding a wet one. You get a written price after we trace the leak.
Typical timeline
A recoat over a sound deck usually takes a few days including cure time. Rebuilding plywood, slope and flashing takes about one to two weeks, depending on weather.
Backed by a 24-month workmanship warranty
Written scope
You know exactly what is included before work starts, with photos of what we found.
Our own crew
The people who quote your job are the people who do it, start to finish.
Clean site daily
Debris is hauled away and your yard is left the way we found it.
24 months covered
If our workmanship fails within two years, we come back and make it right.
What homeowners near Sammamish say
“I had a great experience working with Eco Home Repair on a water damage project. Water was leaking into the house through the chimney, which caused mold and water damage issues. Eco Home Repair handled everything smoothly and professionally. They replaced the…”
“I hired Eco Home Repair to do a leak repair under my balcony, deck waterproofing and slope correction, and underlying rot repair. They were professional, quick, and fairly priced; kept me in the loop throughout the whole process and was honest about what…”
“One of my windows leaked after I had them cleaned and so I called Eco Home Repair to take a look. I really appreciated the thorough inspection - they determined the leak was unique to the aggressive window washing and wouldn't happen in regular rain (it had…”
5.0 average from 106 reviews on Google, Thumbtack, Angi, HomeAdvisor and Yelp. Read our reviews on Google.
Questions Sammamish homeowners ask about waterproofing
My Sammamish home has original hardboard siding. Should I repair or replace it?
Can you coat over my existing deck in Sammamish?
Why is water leaking under my deck or balcony?
What is kick-out flashing?
How often should a deck coating be recoated?
More from our crew in Sammamish
Waterproofing near Sammamish
Tell us about your waterproofing project in Sammamish
- Licensed, bonded & insured
- Free on-site estimates
- 24-month workmanship warranty
Book a free waterproofing inspection in Sammamish
We inspect the damage on-site, show you photos of what we find and give you a written price before any work starts.