Roof Repair in Miami : Chimney
By Michael Slattery
There are a lot of chimneys in Miami though they rarely see action and are a common source of roof repair calls for roofers. Leaks around chimneys are usually attributed to improperly installed metal flashings, as was this one.
This concrete tile roof, only 15 years old, had rotten plywood across a large area immediately below the chimney, the structure of which was solid. The stucco-stop counter-flashing was sloppy so the base flashings were also suspect and, after removing some roof tiles, our suspicions were confirmed.
We tore out everything on all four sides and replaced a full sheet of plywood. This chimney was 50” X 50” and Code requires a “cricket” be built on the upslope side of a chimney more than 30” wide to allow water to flow freely from behind it.
We dried everything in with 30 lb. felt and installed galvanized base metal flashings. Most roofers in Miami use 4” X 5” but for this roof repair we spent the extra few bucks on 5” X 7” flashings for better overall performance – a “bigger flash”. This installation is a skill requiring precise cutting and bending of the metal while setting and nailing the individual pieces in flashing cement. We spend the extra few bucks on top grade modified roof cement. Standard roof cement deteriorates faster and is the cause of many leaks in flashing areas. It is amazing how many flashings fail after 10-15 years simply because cheap roof cement quickly dries up and shrinks. The flashings are then coated with asphalt primer to ensure good adhesion of the underlayment.
Stucco-stop counter-flashes the base metal flashing and also requires a professional skill set. It is typically attached to the wall with 1 1/4” drive pins and sealed with a bead of calk across the top. We’ve seen many of these caulk beads fail and cause leaks so we don’t mind spending a few extra bucks to caulk the back side where it contacts the wall to provide a 100% foolproof seal.
The installation of tile underlayment, the waterproofing component of a tile roof, was next. We favor self-adhered modified underlayment over the centuries-old hot tar and 90 lb. methods which simply can’t stand the heat in South Florida. Over the years we’ve used a few different underlayment’s and checked out a half dozen others. We have settled on Tarco Leak Barrier PS200HT, a premium, SBS modified, glass fiber reinforced underlayment. PS200HT is made with a specially engineered polymer formulation that allows the underlayment to withstand high temperatures. The cost of a roll of PS200 is almost three times that of a roll of 90 lb. but this technology allows for a more durable system and easier installation without hot tar. 16” valley flashings on the new “cricket” were then installed, primed and stripped with PS200. Then we pressure-washed the chimney and painted it with an elastomeric coating. The tile were put back using Tile Bond adhesive, an expanding polyurethane foam, and the caps and valley were mortared - done.
When a chimney shows signs of poor workmanship we favor a total rebuild over a local fix that only addresses the current leak and leaves the door open for future problems. Our 3-year workmanship warranty leaves the homeowner with comfort in the knowledge that our roof repair is designed to outlast the existing roof. Other Miami roofers sometimes ask me, “How can you offer 3-year warranties?!” It’s simple – we do a complete job and don’t mind spending the extra few bucks.