Florida Certified Roofing Contractor CCC 1334537
Why are the seams on my low-slope roof splitting and opening up?
A straight answer from a Florida certified roofing contractor — then what you can check yourself and when to call. Free quote: (954) 775-8990.
Seams on a low-slope roof usually open because the membrane is being pulled apart by heat movement, UV aging, standing water or a weak bond made at installation. Often several of these are working together, and once a seam opens, rain can get under the membrane and make the problem worse.
The nuance is that a single open seam and widespread splitting mean different things. One failed lap can be a local workmanship or flashing problem that a repair fixes. Seams opening across the roof usually mean the membrane is aging out or the roof has a drainage or movement problem that must be corrected, or the repair will fail again.
Why seams split and open
Florida's sun heats a dark, flat roof surface hard, then a summer thunderstorm can cool it quickly. That daily expansion and contraction stresses every lap and edge. Over time, UV and heat dry out the asphalt in modified bitumen and built-up roofing, so the membrane loses flexibility and can no longer stretch with that movement. The seam is the weakest line, so it opens first.
Ponding water is another common cause. Where slope or drains fall short, water that sits on the roof for long periods speeds up membrane aging and puts constant load on laps. Clogged drains or scuppers, low spots in the deck and missing tapered insulation or crickets can all keep water in place.
Installation quality matters too. A lap can be poorly bonded if the surface was dirty or damp, the torch or hot asphalt was applied inconsistently, or a self-adhered sheet was not pressed down well. Movement underneath, such as insulation board joints or deck seams, can also telegraph up and crack the membrane along a line. Seams at parapets, curbs and edges take extra stress from wind uplift and from flashing that has pulled away.
What you can check yourself (without going on the roof)
Look at the ceiling
Stains, bubbling paint or damp spots that show up or grow after rain suggest water is getting past a seam or flashing. Note where they are, since that helps a roofer locate the entry point.
Check the attic or deck underside if accessible
Look for damp insulation, dark stains or a musty smell on the underside of the roof deck. Only do this where there is safe, normal access.
Watch for ponding from the ground or a window
From a safe vantage point, look at whether puddles linger well after the rain stops. Standing water points to a drainage or slope problem behind the splitting.
Look at drains and scuppers from the ground
Overflowing, stained or blocked scuppers and downspouts can mean water is backing up on the roof.
Take photos and notes
Photograph what you can see from the ground or from inside, with dates. Skip the roof coating or tar you can buy off the shelf, because covering a seam can hide the cause and complicate a proper repair.
When to call a pro
Call if you see interior leaks, seams opening in more than one place, ponding that does not drain, or membrane that is cracking, lifting or pulling away at walls and edges. Open seams get worse with every heavy rain, and wet insulation or deck can be damaged if the water is left alone. A roofer needs to see the roof to tell a local lap repair from a membrane at the end of its life.
Roofing work is regulated. The state puts it this way: "Roofing work in Florida legally requires a licensed roofing contractor and generally a permit from the local building department; a contractor's license is verified on the Florida DBPR website." Condominiums and HOAs often require their own approval in addition to the permit. If a repair covers a large part of the roof, Florida's 25% roof rule may come into play: "Florida's 25% roof rule (Florida Building Code, Existing Building volume, section 706.1.1): when more than 25% of a roof or roof section is repaired, replaced or recovered in any 12-month period, the entire roof or section has to be brought up to current code." Check with your city or county building department on how it applies to your roof. We can walk you through the options, and the estimate is free.
What a pro will do
- Find the real causeWe look at the seams, flashing, drains and ponding areas together, rather than only patching the opening that shows.
- Repair or re-lay the failed areasDepending on what we find, that can mean repairing laps, modified bitumen or torch-applied cap sheet sections, or replacing the system if it has aged out.
- Correct drainageTapered insulation, crickets, new drains or scuppers can take away the ponding that keeps stressing the seams.
- Redo base flashingParapet and curb flashing is rebuilt where it has pulled loose, since that is a frequent point of water entry.
- Deal with the deck and the paperworkIf wet or rotten deck is found, it is replaced. We pull permits under our own license, schedule and pass inspections, close the permit, and leave the site cleaned up. Your written flat-rate quote says what is included.
Related questions
- Can I just seal the split seam with roof cement?
- A dab of sealant over an open seam may slow a leak briefly, but it usually does not fix the cause, such as movement, ponding or a brittle membrane. It can also make a proper repair harder, because the area has to be cleaned and dried first. A roofer can tell you whether a repair is realistic.
- Is a split seam a repair or a sign I need a new roof?
- It depends on how widespread the splitting is and what condition the membrane and insulation are in. A few isolated open laps can often be repaired, while splitting across the roof, saturated insulation or repeated leaks may point toward replacement. We can inspect it and put the answer in a written quote.
- Do I need a permit to repair low-slope roof seams?
- A permit from the local city or county building department is typically required for low-slope reroofing, recovers and most repairs. Confirm the details with your building department, and check with your association if you live in a condo or HOA.
- Do roofing products have to be approved for my area?
- Yes. The rule is: "Miami-Dade and Broward are Florida's High-Velocity Hurricane Zone. Roofing products used there need a Miami-Dade Notice of Acceptance (NOA) for that use; elsewhere in Florida they need a Florida Product Approval (or local approval). Either way the product is installed per its approval."
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