Deck Waterproofing & Flashing
A deck or balcony over a living space has one job: keep water out of the rooms below. 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.
Before
AfterFlashed and rebuilt
Waterproofing done the lasting way
Most rot starts with a small leak in the wrong place: a deck coating that wore through, a door with no sill pan, a roof edge with no kick-out flashing. Waterproofing and flashing are the details that decide whether a repair lasts two years or twenty. We find the path the water takes and close it.
When to call about waterproofing
- Stains or drips on the ceiling below a deck or balcony
- Cracked, peeling or soft deck coating
- Water pooling against the house after rain
- Rot or stains under windows and doors
- Streaks down the wall below a roof edge
- A deck that slopes toward the house
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
Waterproofing services
Walkable deck coatings
Waterproof coating systems for decks and balconies over living space.
Slope correction
Fix flat or back-sloped decks so water drains away from the wall.
Door and sill pans
Pan flashing under doors, where many balcony leaks start.
Kick-out flashing
Diverts roof water away from the wall at roof-to-wall joints.
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.
Waterproofing: things to weigh before you decide
Why coatings fail
Coatings fail at edges, doors and posts long before the open surface wears out. Recoating without fixing those details only buys a season or two.
Coating over old decks
If the plywood is solid and dry, we prep and coat. If it is soft or wet, it is replaced first, because a coating cannot fix a rotten substrate.
Flashing is cheap insurance
A kick-out flashing or a door pan costs little compared with the wall it protects. We add them wherever they are missing on the area we repair.
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
| 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 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.
A 10-minute check homeowners can do
- Look for stains or drips on ceilings below a deck or balcony
- Check the deck coating for cracks, peeling or soft spots
- Watch where water goes during heavy rain
- Check thresholds and the walls next to deck doors
- Look for missing kick-out flashing at roof edges against walls
- Make sure deck drains and scuppers are clear
If you find one or two of these, it is worth a look before the next wet season. Small problems caught early are usually a short, inexpensive repair. Left alone, water keeps spreading into framing and the repair grows.
Not sure what you are looking at? Send us a few photos with the form below or by text to 425.600.7002 and we will tell you honestly whether it needs attention now.
Waterproofing: what you should know
Why it happens
Worn deck coatings
Coatings wear through first at doors, edges and posts, and water reaches the plywood underneath.
Decks that slope toward the house
Flat or back-sloped surfaces push water against the wall and door thresholds.
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 every waterproofing job includes
- Leak tracing with moisture readings and inspection openings
- Replacement of wet or rotted plywood and joists
- Slope correction so water drains away from the wall
- Sill pans, door flashing and wall flashing
- Primer, membrane and walkable top coat in layers
- Kick-out and head flashing where needed
- A water test of the repaired areas
Keeping it from coming back
- Recoat deck surfaces when the top coat starts to wear
- Keep drains and scuppers clear of leaves
- Do not drag furniture across coated decks
- Check caulk at doors and walls every year
- Fix small leaks before they reach the framing
What drives the price
Waterproofing in your area 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.
Why homeowners call Eco Home Repair
Homeowners in your area call us for leaks because we find the source before we seal anything. We fix the substrate, the slope and the flashing, not just the surface, and we back the work with a 24-month workmanship warranty.
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 say
“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…”
“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…”
“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.
Waterproofing across the region
Our climate is the same everywhere we work, but each part of the region wears houses out a little differently.
North Snohomish & Skagit
Open lots, steady rain and many 1990s–2010s subdivisions with builder-grade flashing that is now reaching the end of its life. For waterproofing, we see the same pattern again and again: worn coatings and missing flashing let water into walls and ceilings.
Everett & the Sound
Older homes near the water take wind-driven rain and salt air, so trim, siding and decks facing the Sound wear out first. For waterproofing, we see the same pattern again and again: worn coatings and missing flashing let water into walls and ceilings.
South Snohomish County
Tree-covered lots and shaded north walls keep wood damp for months, and many homes still have original siding and decks. For waterproofing, we see the same pattern again and again: worn coatings and missing flashing let water into walls and ceilings.
Mill Creek, Bothell, Snohomish, Martha Lake, Lake Stickney, Brier, Mountlake Terrace
Eastside & North King County
Large decks, view balconies and cedar details on homes from the 1960s to today, many of them on sloped, wooded lots. For waterproofing, we see the same pattern again and again: worn coatings and missing flashing let water into walls and ceilings.
Woodinville, Kirkland, Redmond, Bellevue, Sammamish, Kenmore, Medina, Mercer Island
Seattle & Shoreline
Older housing stock with original wood windows, porches and siding, often with little or no weather barrier behind it. For waterproofing, we see the same pattern again and again: worn coatings and missing flashing let water into walls and ceilings.
Waterproofing in your city
We do waterproofing in 29 cities across Snohomish and King County.
Not listed? We may still cover you. Call 425.600.7002.
Waterproofing: common questions
Why is water leaking under my deck or balcony?
How long does a deck coating last?
Can you coat over my existing deck near me?
What is kick-out flashing?
Do you fix leaks around windows?
Can you waterproof a deck over a living space?
How often should a deck coating be recoated?
Why does my ceiling leak only in heavy rain?
Other repairs we do
Dry Rot Repair
We find where the water gets in, cut out every soft spot and rebuild it so it stays dry.
Dry Rot Repair detailsDeck Repair & New Decks
Repairs, rebuilds and new composite decks, built on solid framing with the flashing done right.
Deck Repair & New Decks detailsSiding Repair & Replacement
Siding repair and replacement with the house wrap and flashing done right behind it.
Siding Repair & Replacement detailsStructural Repair
Rotted posts, beams, joists and sill plates replaced and reinforced, with shoring when needed.
Structural Repair detailsWindow, Door & Trim Repair
Rotted sills, jambs and trim replaced, with flashing so the water stops getting in.
Window, Door & Trim Repair detailsChimney Chase Repair
Rotted wood-framed chimney chases rebuilt, sided and flashed so they stay dry.
Chimney Chase Repair detailsFascia & Soffit Repair
Rotted fascia, soffits and rafter tails replaced, with drip edge so the roof edge stays dry.
Fascia & Soffit Repair detailsBalcony & Porch Repair
Rotted balconies, porches, columns and railings rebuilt safely and waterproofed.
Balcony & Porch Repair detailsTell us about your waterproofing project
- Licensed, bonded & insured
- Free on-site estimates
- 24-month workmanship warranty
Book a free waterproofing inspection
We inspect the damage on-site, show you photos of what we find and give you a written price before any work starts.