Hidden water intrusion from ocean-facing deck/sliders — mold below with no visible leak
1980 ocean-facing townhouse in South Jersey with a hidden water intrusion nobody can properly diagnose.
Second-floor deck and sliders were redone about 10 years ago. Two Andersen 200 Series sliders face the ocean. Deck appears to be concrete with some type of fiberglass/waterproof coating under Trex decking.
One concern is the deck and interior floor/sliders are basically at the same elevation with very little height difference between exterior deck and interior floor. Some contractors think the sliders may need to be elevated/rebuilt properly.
There is also concrete under the carpet inside and mold was found under the carpet near the slider area.
Another factor is there is no roof overhang or covering protecting the deck/sliders. The deck is fully exposed to coastal wind-driven rain facing the ocean.
Issue started Sept 2025:
- Mold first appeared at the upper wall/ceiling area near the sliders on one side
- Over time it slowly migrated inward along where the ceiling meets the walls and later appeared on the opposite side as well
- It is now also beginning to show on the front wall/ceiling area directly below the sliders facing the ocean
- No visible dripping water
- Moisture meter shows elevated moisture
- Thermal camera confirms intrusion but not exact entry point
We’ve had multiple contractors look at it and opinions are all over the place:
- failing deck membrane
- slider flashing/pan failure
- actual slider/frame failure
- slope/drainage issue
- or combination of all of the above
Problem is nobody wants to do actual diagnostics. Mostly visual inspections only. No controlled hose testing, flood testing, UV/dye testing, borescope/wall camera inspection, lifting Trex boards, or invasive diagnostics/opening areas.
A lot of “leak detection” companies in South Jersey mainly deal with plumbing/pool leaks, not building envelope or structural water intrusion. Most contractors are basically guessing based on thermal camera/moisture meter readings, which only show where moisture exists, not where it’s entering.
I’ve also contacted engineering firms and forensic-type consultants, but many either:
- handle much larger commercial projects
- are too busy
- want plans/drawings
- only do visual inspections
- or are too far away to take a smaller residential investigation like this
Mold remediation company says leak source must be resolved first.
We’re the only unit out of 6 attached ocean-facing townhouses having this issue.
At this point I’m trying to figure out:
- Who normally handles this type of investigation?
- Is this more likely deck waterproofing, slider flashing/pan, the sliders themselves, elevation issue, or all combined?
- Is controlled water testing usually the next logical step?
- Has anyone dealt with a concealed leak like this where mold appears long before visible water?
Trying to solve the actual root cause correctly and not just throw caulk/coatings at it and hope for the best.