Deck Waterproofing & Membrane Repair in Seattle & the Puget Sound Region
Decks and elevated exterior surfaces are a frequent source of hidden water intrusion, especially when waterproofing membranes fail or were improperly installed. Because decks often sit over living space, leaks can cause interior damage long before problems are visible from above.
Synapse Construction provides deck waterproofing and membrane repair throughout Seattle, the Eastside, and the greater Puget Sound region, with a focus on identifying membrane failures and restoring proper drainage and waterproofing at deck-to-building transitions.
What’s Happening
Deck waterproofing systems are designed to manage water exposure, but over time they can fail due to:
- Aging or deteriorated membranes
- Improper slope or drainage
- Failed flashing at deck-to-wall transitions
- Inadequate waterproofing at railings, doors, or penetrations
- Previous repairs that addressed surface symptoms but not the membrane below
When water bypasses the membrane, it can migrate into wall assemblies or interior spaces below the deck.
Why Deck Waterproofing Failures Are Urgent
Water intrusion at decks often goes unnoticed until damage becomes significant. Delaying repair can result in:
- Rot in framing and structural components
- Damage to ceilings, walls, and finishes below
- Mold growth and indoor air quality concerns
- Compromised deck safety
- Increased repair scope and cost
Early investigation can often limit repairs to targeted areas rather than full deck replacement.
How Synapse Construction Handles Deck Waterproofing Repairs
Our approach begins with understanding how water is moving through the deck assembly.
A typical deck waterproofing and membrane repair may include:
- Exterior inspection of deck surfaces, edges, and penetrations
- Evaluation of slope, drainage, and existing membrane conditions
- Selective removal of deck finishes to expose the waterproofing layer
- Repair or replacement of failed membranes
- Installation of proper flashing at deck-to-wall and door transitions
- Restoration of deck surfaces and finishes
We focus on durable waterproofing solutions that protect both the deck and the structure below.
Common Deck Waterproofing Issues We Find
During inspections and repairs, we frequently uncover:
- Membranes that have reached the end of their service life
- Inadequate flashing where decks meet walls or doors
- Water trapped due to insufficient slope
- Penetrations that were never properly sealed
- Concealed rot beneath intact deck surfaces
Many of these conditions are not visible without investigation.
Photos & Repair Examples
When to Start With a Water Intrusion Inspection
If leaks are appearing below a deck or the source of moisture is unclear, starting with a water intrusion inspection can help identify whether the deck membrane or an adjacent transition is the cause.
→ Learn more about Water Intrusion Inspections
Service Areas
We provide deck waterproofing and membrane repair services throughout:
Seattle Neighborhoods • Eastside Communities • Greater Puget Sound Area
Schedule a Deck Waterproofing Evaluation
If you’re noticing leaks, staining, or moisture below a deck or elevated exterior surface, early evaluation can help prevent more extensive damage.
Contact Synapse Construction to schedule a deck waterproofing and membrane repair assessment.
