Sika Sarnafil Roofing in Brockton, MA
A welded roof is only as good as its worst weld. Owners of a Sika Sarnafil PVC roof in Brockton, MA often assume the sheet is the weak link. It rarely is. The weak link is a weld made on a damp day, a flashing that pulled at a corner, or a drain that backed up under snow. We probe the welds and find out.
Sika Sarnafil makes thermoplastic roofing membranes, most commonly PVC. The sheets are joined with hot-air welds that fuse the laps into one piece. PVC resists many oils and chemicals better than some other single-ply sheets, which is why it shows up over kitchens and process areas. That strength means little if a weld is cold.
Probe every weld, not just the leaking ones
A weld that leaks is easy to find. A weld that is about to leak is not. Dust, damp, or a cool surface at the time of welding can leave a patch of weak fusion. From above it looks like a clean line, and a blunt probe run along the lap finds the soft spot.
Our process is plain. The probe runs the whole lap, and each soft stretch gets marked. We clean both sides of the weak area, weld sound sheet to sound sheet, and probe once more after it cools.
The visible lift is almost always shorter than the weak stretch. A patch over only the visible lift leaves the weak part to open later. We follow the probe, not the eye.
Welding quality also depends on the sheet itself. Old PVC that has lost plasticizer turns stiff and will not fuse cleanly, and a weld on brittle sheet cracks beside the line rather than along it. When a test weld on aged membrane will not take, we say so, and the repair becomes a larger piece cut back to flexible sheet, or the roof moves toward replacement.
Know the cold limits on welding and cleaning
Brockton's record low is minus 19 degrees, and about 34 inches of snow fall in a typical year. Hot-air welding needs a dry, clean surface. Frost, ice, and damp stop a good weld, and in a hard winter the roof may be unworkable for weeks.
So we split the work. In deep cold we set a temporary patch to keep water out and record it. When the sheet is dry and the air is workable, we make the permanent weld. The report lists both dates, and the owner should not confuse the patch with the fix.
Snow cover hides problems and a thaw reveals them. February is the heaviest snow month, at nearly 13 inches. We schedule a walk in the first dry stretch after a thaw to look for new openings, the kind that become wet ceiling tile by the following week.
Ice adds its own damage. A drain frozen shut sends meltwater to the nearest lap, and chipping at the ice with a pointed tool cuts the sheet. We clear drains with heat and patience, not with a pick.
Rebuild the flashing where the sheet turns up
Thermoplastic sheets are fused to prefabricated flashings and trim at walls, curbs, and pipes. Movement pulls those joints. Heat expands the sheet, cold shrinks it, and where it is held at a wall the stress concentrates at corners.
We check each corner and each termination for pulled welds, lifted metal, open sealant, and cracked boots. A failed corner gets cut back to sound sheet and rebuilt with a new flashing welded in. A termination bar gets re-fastened and sealed. A penetration flashing check covers every pipe, vent, and curb, not just the one over the stain.
A parapet cap that has lifted lets wind-driven rain behind the flashing, and Brockton's wind averages 14.3 mph. We fix the cap first.
Check the fasteners and the edge together
Many PVC roofs are held down with mechanical fasteners set along the sheet edge, and others are fully adhered. The fastening pattern matters in wind. The region has seen a 121 mph sustained wind in the 1938 hurricane and a Category 2 landfall from Bob in southeastern Massachusetts in 1991, and ordinary nor'easters still bring hurricane-force gusts.
On a fastened roof, we look for backed-out fasteners, torn plates, and a sheet that billows in a breeze. On an adhered roof, the perimeter bond gets tested by hand. At the edge we look at the metal, because loose coping lets wind under the sheet.
The fix is plain: re-fasten, replace torn plates, re-secure the metal, and renew the termination, the same steps a Duro-Last or GAF PVC roof gets. Then we walk the whole perimeter. A coping and edge metal repair done before a storm costs a fraction of a membrane repair after one.
Match the sheet to what vents onto the roof
Kitchen exhaust, laboratory vents, and process stacks put grease and vapor on a roof. Some membranes soften under that exposure. PVC is often chosen for those roofs because it resists many oils and chemicals, though the choice still depends on what vents where.
Brockton has three hospitals, among them Boston Medical Center - South and the Brockton VA Hospital, and Plymouth's largest employer is Beth Israel Deaconess Medical Center. Hospital roofs often carry kitchens, labs, and mechanical vents, and a PVC roof near the Avon Industrial Park off Route 24 or on the Brockton VA campus gets the same discharge survey. A survey records every discharge point and the sheet condition around it, and where wear shows we recommend a resistant membrane, a grease container, or a stack extension. Grease that lands on a lap softens sealant and lifts a flashing corner, so those corners get checked first. What a given roof has comes from a core and a walk. Occupied care buildings add sequencing limits that shape every hospital roof job.
Keep a weld log the next inspector can read
Every weld we touch is logged with a photo, a location on the roof plan, the length probed, and the date. A year later the next visit compares against it. If a weld we repaired is holding, the log says so. If a different one is opening, the log shows where.
The warranty file holds the paperwork beside the log, since a manufacturer warranty may set conditions for repairs and notice. For an owner with more than one building, a consistent log format lets roofs be ranked, with the most open welds and the wettest core first. That ranking is the base of a repair budget that holds up in front of a lender or a board. A core and a moisture map decide repair or replacement, and the price lines stay separate. In Plymouth or Brockton the steps are the same.
Commercial Roofing Questions
How can a weld fail if it looks fused?
Dirt or damp at the time of welding leaves a weak spot. Only a probe finds it.
Can welding be done in winter?
Only on a dry, clean sheet in workable air. Otherwise we use a temporary patch and weld later.
Does PVC handle kitchen exhaust?
Often better than some sheets. We still check the surface near each fan and fit grease containment.
Do I need new flashing or just sealant?
New flashing when the old one has pulled or cracked. Sealant alone is a temporary hold, and a corner that keeps reopening means the flashing was cut too tight for the movement it carries.
When is a PVC roof past repair?
When wet insulation spreads across sections or welds fail in many places. A core and a probe count settle it, and the owner sees both numbers before any replacement price is written.