Somerton Philadelphia Roof Replacement: Row Home

Somerton Philadelphia Roof Replacement: Row Home Case Study

When the Leak Follows You From Room to Room

This Somerton, Philadelphia, roof replacement project began with a call from a homeowner who had been chasing a leak for two years. She had a row home on one of Somerton’s tree-lined streets, a flat roof that had been patched twice by two different contractors, and a water stain on her bedroom ceiling that moved with the seasons. The last crew had told her the roof was “fine for a few more years.” It was not fine.

What We Found During the Inspection

Our inspection covered the roof surface, the parapet walls, the drains, and the ceiling from the attic access. What we found explains why the patches hadn’t worked:

The primary drain was partially blocked by years of debris accumulation and a failed drain strainer that had collapsed inward. Water had been ponding in the center of the roof after every significant rain event. The modified bitumen membrane directly around the drain showed bubbling and delamination — the membrane was lifting from the deck below due to sustained water pressure.

The parapet wall flashing on the north side — the wall shared with the attached neighbor — had separated at the top edge where the counterflashing met the brick. This is one of the most common failure points on Northeast Philadelphia row homes and one of the most frequently missed during casual patch inspections. Water was wicking down behind the membrane on the north perimeter and traveling along the top-floor ceiling joists before appearing as a stain in the bedroom.

Three sheets of roof decking directly around the drain had soft spots indicating moisture damage that had been progressing for at least two seasons. The membrane hadn’t failed catastrophically — it had been slowly allowing water through multiple small points simultaneously, which is why patches at any one spot hadn’t solved the problem.

Our Solution — What We Did and Why

Full membrane tear-off to bare decking was the only correct approach. Patching over failed decking creates a new membrane that looks good from the street but fails within two to three seasons because the underlying substrate continues to deteriorate.

We replaced the three damaged decking sheets with matching plywood and treated the surrounding area to address moisture before installing the new material. The drain was replaced with a new cast-iron drain and a properly sized strainer. The drain collar was set slightly low to encourage positive drainage toward the drain rather than away from it.

We installed a new two-ply modified bitumen membrane — torch-applied for a fully bonded, seamless surface — with a 3-inch overlap at all seams. The north parapet wall received a full counterflashing replacement, with a new reglet-cut termination into the brick, creating a proper watertight seal at the shared wall.

The parapet cap flashing and all four corners received new metal cap flashing to complete the perimeter waterproofing system.

The Process — What the Homeowner Experienced

Day one: full membrane tear-off by 11 am. Decking inspection, replacement, and drain installation completed by the end of the day. The roof was temporarily weatherproofed with underlayment before the crew left — no overnight open exposure. Day two: torch-applied modified bitumen membrane installed in two plies, all parapet and counterflashing completed, drain connected and tested with a bucket of water, and cleanup completed by mid-afternoon.

The homeowner noted that the crew arrived when they said they would, covered her skylights and a rooftop access hatch to prevent debris entry, and left the block cleaner than they found it. In a Somerton row-home block where parking is tight and neighbors notice everything, job-site courtesy matters.

The Result

The bedroom water stain is the last record of the problem. The roof has since been through two winters, multiple nor’easters, and a summer of heavy convective storms without a single leak call. The drain flows freely. The north parapet counterflashing is fully sealed. The homeowner has the written warranty and the L&I permit close-out documentation to present at the sale.

What This Project Taught Us

The most expensive roofing mistakes in Somerton aren’t dramatic failures — they’re slow, incremental problems that get patched rather than diagnosed. A contractor who patches a leak on a flat row home roof without inspecting the drain, the parapet flashing, and the decking condition underneath is almost certainly charging you for a temporary fix. Call Paragon Exterior at (215) 799-7663 for a proper diagnosis before approving any patchwork on your flat roof.

Frequently Asked Questions

How long does a flat roof replacement take on a Somerton row home?

A standard flat roof replacement on a Somerton row home takes one to two days — one day for tear-off and decking inspection, and one day for membrane installation and flashing work. Drain replacement and parapet counterflashing can add a half-day. Paragon Exterior provides a specific timeline in every written estimate.

What causes flat roofs on Somerton row homes to fail early?

The most common causes are: clogged or deteriorated drains that allow ponding water, failed parapet wall counterflashing that allows water to wick under the membrane at the perimeter, and aging modified bitumen seams that split under freeze-thaw cycling. Proper drainage is the single most important factor in the longevity of flat roofs on row homes in Northeast Philadelphia.