A deck that has been part of a home for a hundred years carries a certain character — but it also carries a century of weathering, membrane fatigue, and water infiltration that eventually demands a real solution. For one Dayton homeowner, that reality had made itself known through persistent leaks pouring into the sunroom directly below her third-story deck. The deck surface had long since lost whatever waterproofing it once had, and every rainfall was finding its way through.
The deck itself sits on the third story of the home, enclosed by a dark wrought-iron railing system and overlooking a backyard with a stone fireplace feature below. At that height and with that much age behind it, the surface couldn’t simply be patched and hoped for — it needed a system that would bond to the existing substrate, seal every edge and corner, and hold up through Ohio’s full range of seasonal conditions for years to come. CPM ROOF delivered exactly that with a Henry silicone coating system backed by a 10-year warranty.
What a Century of Age Does to a Deck Surface
Flat and low-slope deck surfaces rely on a continuous waterproofing membrane to keep water from migrating through the substrate below. Over decades, those membranes oxidize, crack at seams, and pull away from edges and penetrations — all the places where water is most likely to find a path downward. On a structure that had been in place for a hundred years, the membrane had reached a state of failure across the entire field rather than in isolated spots.
Leaks over a sunroom are particularly damaging because the sunroom ceiling and structural members below absorb moisture before it ever becomes visible as a drip. By the time a homeowner notices water coming through, the damage to the material below the deck surface is typically already significant. The right response wasn’t a spot repair — it was full waterproofing coverage from edge to edge.
Why Silicone Was the Right Solution
Henry silicone coating is one of the most effective waterproofing systems available for flat deck and low-slope surfaces because it bonds directly to the existing substrate, remains permanently flexible through freeze-thaw cycles, and maintains full waterproofing integrity even when water sits on the surface. Unlike acrylic coatings that can re-emulsify when wet during application or harden and crack over time, silicone cures to a durable, rubber-like membrane that moves with the structure rather than against it.
On a third-story deck that experiences foot traffic, furniture weight, and Ohio’s full temperature range from summer heat to winter freeze, permanent flexibility isn’t optional — it’s what keeps the coating intact over the life of the warranty. Silicone also doesn’t require the deck to be torn down to bare substrate before application, which made it a practical and cost-effective solution for a structure of this age.
Prep Work and Surface Cleaning
Before any silicone went down, the deck surface was thoroughly cleaned and prepared to ensure proper adhesion across the full field. Any loose or compromised material was addressed, and the perimeter edges — where the deck surface meets the wrought-iron railing bases and the exterior wall of the home — were cleaned and prepped to receive the coating in those critical transition zones.
Adhesion at the wall-to-deck transition is one of the most important details on any deck waterproofing project. That joint is where thermal movement concentrates and where water tends to collect along the siding. Getting the silicone to bond tightly and continuously at that interface is what determines whether the system stops the leak or just pushes it to a different location.
Edge and Corner Detailing
The corners where the deck surface meets the railing base plates and the perimeter edges where the coating terminates against the wall were detailed with additional silicone passes to build up thickness and ensure continuous coverage. On a deck with wrought-iron railings set into the surface, those railing base penetrations are each a potential entry point for water if they aren’t addressed as part of the coating system.
Every base plate and perimeter transition was sealed into the silicone system rather than left as a gap between the new coating and the existing metal or wall material. That level of edge detailing is what makes the difference between a waterproofing job that lasts through the warranty period and one that starts showing problem areas within a couple of seasons.
Wall Transition and Siding Interface
Where the deck surface meets the exterior wall of the home, the silicone was applied up the wall face to create a positive seal that water cannot travel behind. The white lap siding on the home’s exterior comes down close to the deck surface, and the gap between siding and deck is exactly where older waterproofing systems tend to fail first. The silicone coating was carried up the wall and dressed tight to the siding to close that joint permanently.
Getting this detail right also protects the siding itself. Water that migrates behind a deck membrane and into the wall cavity doesn’t stay in the wall — it works its way through the sheathing, insulation, and interior finishes of the home over time. Sealing that transition stops the problem before it spreads laterally into the wall assembly.
The Finished System and 10-Year Warranty
Once the full coating was applied and cured, the deck presented a clean, uniform dark gray surface from railing post to wall — continuous coverage with no gaps, joints, or exposed seams anywhere across the field or at the perimeter. The homeowner could put her outdoor furniture back on a surface that was fully sealed and warranted for a decade.
The 10-year warranty backed by Henry’s commercial-grade silicone product gives this homeowner something the previous surface never had: documented, transferable protection and the confidence that the leaks into her sunroom below are done.
CPM ROOF | Deck Waterproofing & Flat Roof Coating | Miamisburg & Franklin, OH
CPM ROOF provides silicone deck waterproofing, flat roof coatings, and commercial membrane systems throughout the greater Dayton area. Whether the surface is a residential deck, a low-slope roof, or a historic structure that needs a modern waterproofing solution, the team delivers systems built to last. Call (937) 860-2925 to schedule your inspection today.