Clearing, resealing and re-detailing the outlets that take water off a low-slope rowhouse roof.
Fastest: call (833) 751-2102. Or send this and we call you back.
A low-slope roof drains through one outlet: an internal drain, a scupper through the parapet or cornice, or a gutter along the facade. Repair work clears it, reseals the flange or sleeve where the covering meets it, and proves the flow with water. Call (833) 751-2102 for a local roofer.
On a rowhouse the outlet is the single most important square foot of the roof. Everything else is sloped toward it at a minimum of a quarter inch per foot, according to the city's homeowner guide, so when it stops working the whole roof becomes a shallow tank.
There are two routes the water can take. It can go through a drain that passes the cornice or parapet as a scupper and joins a downspout on the outside of the building, or it can run to a gutter along the facade, which the same guide notes is more common at the rear.
Either way the outlet is a deliberate hole in the waterproofing sitting at the lowest and wettest point of the roof. That is why drain and scupper seams appear on every list of trouble spots for this roof type, alongside parapet flashing and ponding.
Because a parapeted roof has nowhere else to send it. There is no eaves to overflow and no overhang to spill past, so water rises against the parapet upstands and the party-wall terminations until it finds the weakest joint. A gutter at the eaves spills outward; this one spills inward.
Depth builds faster than people expect on a small roof, and standing water loads every seam it covers continuously rather than for the length of a shower. A roof that would have shed a storm without noticing can leak in three places because one strainer was packed with granules.
This is also why clearing the outlet is sometimes the whole repair. On a night call in heavy rain, a blocked drain is as likely a cause as a hole, which is why a roofer attending an emergency checks the outlet before reaching for a patch.
Through the joint rather than the pipe. The flange or clamping ring where the membrane is dressed into the bowl is a mechanical seal that can loosen, corrode or lose its grip on an aged sheet. Water then travels between membrane and deck while the drain itself keeps running happily.
Those leaks are deceptive because the obvious test, pouring water down the drain, passes. What finds them is ponding the area deliberately and watching the ceiling below, or looking at the deck from inside where that is possible.
The same applies to a through-wall scupper, where the sleeve can be sound while the membrane dressed into it has shrunk back a fraction. On an older roof with several generations of patching around the outlet, that whole detail is often best rebuilt rather than resealed again.
Often yes, and on a roof that ponds repeatedly it is worth asking. A second scupper or an overflow set at a known height means a blockage shows itself as water running down an outside wall rather than as a stain spreading across a top-floor ceiling. Feasibility depends on the wall and the roof.
It is usually a job for the moment the covering is off, because a new opening through a parapet involves masonry and a new membrane detail. Raising it during a flat roof replacement costs far less than retrofitting it into a sound roof.
There are limits. A party wall is shared, a street-facing cornice on a designated building may be subject to Historical Commission review for anything visible from the public right-of-way, and a larger or commercial building can fall under different city rules, which L&I answers for the address.
After leaf fall at minimum, and after any heavy rain or high wind if you have trees nearby. Outlets fill with leaf litter, seed, roof granules and windblown grit rather than dramatically, so the capacity drops over seasons until a single storm finds the margin gone.
There is a winter dimension too. Philadelphia gets some snow most winters in totals that vary widely, and an outlet that is already restricted is the one that freezes and then overflows on the thaw. No snowfall figure appears here because the sources found for it conflicted.
Put it on a schedule rather than a reaction. Clearing a drain is the cheapest roof maintenance there is, and it protects the parapet flashing and the membrane seams that a pond would otherwise sit on.
Never clear a scupper by leaning over a parapet. The wall is low, sometimes loose at the top, and there is nothing beyond it, which makes this one of the most dangerous bits of amateur roof maintenance there is. Do not put a hand or an arm into a drain throat where broken metal and glass collect, do not run a pressure washer into an outlet because it forces water under the covering, and do not use a drain rod on an internal pipe without knowing where it runs. If a roof is already holding water, keep off it and call (833) 751-2102.
Debris comes out of the bowl, the strainer and the throat, and the roofer looks into the pipe or through the wall sleeve rather than assuming the blockage was all on top. Much of the time this one step changes the roof's behaviour.
Water is run or ponded deliberately and watched. How quickly it goes, whether it backs up, and whether anything appears on the wall or ceiling below tells you if the problem is capacity, a partial blockage or a leaking joint.
The flange, clamping ring or wall sleeve is the junction between membrane and metal. The roofer checks whether the membrane is properly dressed into it and whether the fixing is still tight, because a loose ring leaks under ponding even when the drain flows.
An internal drain runs inside the building, where a joint failure means water in a wall or ceiling with nothing visible on the roof. A scupper discharges to an outside downspout, which is checked from the roof down to ground level.
Seals are renewed, a damaged sleeve or dome replaced, the membrane re-dressed, and in some cases the outlet enlarged or an overflow added. Then it is tested again with water before the roofer leaves.
A bowl in the roof surface with the pipe running down inside the building. Convenient and well protected, but a failure anywhere along that pipe puts water inside a wall or ceiling, so the leak often appears a long way from the roof.
A through-wall outlet that takes the water out of the building and into a downspout on the face of the wall. Easier to inspect from the roof and to clear, but the opening sits in the masonry, so its seal is both a flashing and a drainage detail.
Where the roof discharges into a gutter formed along the wall, more common at the rear of a rowhouse. The gutter then becomes part of the waterproofing, which is why it is covered alongside gutter repair and replacement rather than treated as an accessory.
Tell us what's happening and we'll tell you honestly whether it's a quick fix, and what roof drain and scupper repair should cost.
Drains are the defining detail of the city's roof. The continuous brick rows of Center City, Queen Village, South Philadelphia and Fishtown nearly all drain through a single internal drain, a parapet scupper or a rear gutter, so outlet work is the most ordinary roofing call in Philadelphia.
Attached older stock outside the city behaves the same way. The rows and twins of Chester, Upper Darby and Conshohocken have the same low-slope outlets, with permits issued by the city, township or borough rather than Philadelphia L&I, and Camden's by the New Jersey municipality.
Local weather tests outlets with volume and wind rather than ice. The National Weather Service recorded a line of microbursts gusting 60 to 70 mph across West and South Philadelphia and the Lower Merion area within about half an hour, and that kind of wind strips debris off trees and roofs straight into the nearest opening.
Repairs to flat and very low-slope membrane roofs on Philadelphia rowhouses, twins and converted buildings, starting at the drainage path.
Sealing the upstands, copings and party-wall terminations where a Philadelphia rowhouse membrane meets masonry.
Hung gutters, lined box gutters and downspouts on rowhouses, twins and suburban homes across the service area.
Stripping and rebuilding a low-slope roof on a rowhouse, twin or loft conversion, with the drainage and parapet details redesigned rather than reused.
Not sure if you're covered? Check your ZIP code.
Most Philadelphia rowhouse roofs look flat but slope toward a drain, with a minimum fall of a quarter inch for every foot.
Clearing leaf litter off a strainer from a safe standing position on a dry roof is reasonable. Anything that involves reaching over a parapet, working on a ponded surface or going into the pipe is not, and a blocked roof under water is the worst time to learn that.
Usually the scupper or the spout head is blocked, or a joint at the top of the downspout has opened. It can also be an overflow doing its job, which is a sign that the main outlet is restricted and needs looking at.
The strainer keeps debris out of the pipe so a blockage stays on the roof where it can be seen and cleared. A missing or crushed one is worth replacing, because a blockage inside an internal drain pipe is a far more expensive problem.
Yes, particularly with an internal drain, where the pipe runs inside the building and a failed joint can wet a wall or ceiling well away from the roof outlet. It is one of the reasons a leak is traced rather than patched where the stain is.
Only if capacity is the real limit. If the fall across the roof has gone or the deck has dished, water will not reach a larger opening any faster. The survey looks at the fall and the outlet together.
The principle is, but the scale is not. A wide membrane deck may have several drains, different ages of detail around each and rooftop equipment nearby, so each outlet is assessed in its own right rather than as one job repeated.