Whether a flat or low-slope roof is the right call for your house, how rubber and white membranes differ, what Pennsylvania's code and your town ask for, and how we repair and replace them.
A flat roof is never truly flat. It carries a slight pitch toward a drain, a scupper or an edge, and the membrane on top keeps water moving off. When that pitch is lost or a seam opens, the water has nowhere to go but down into your ceiling.
Around Harrisburg and Carlisle the houses are old. In Dauphin County 62% of the homes were built before 1980, and in Cumberland County 53% were. Many of them have a flat section over a porch, an addition or a row house. We get on the roof, look at the membrane, the seams and the deck, photograph what we find, and write the work into a scope you can read line by line.
A flat roof is a good idea when the shape of the house calls for it: a rear addition, a porch, a low row-house roof, a deck over a garage. It is a poor idea when you are picking it only to avoid a pitched roof on a house that already has one.
Our weather decides how well it works. This area sits in IECC climate zone 4A, with about 101.5 nights a year at or below 32F and 17 days a year when the high stays below freezing. Water that stands on a membrane freezes, thaws and freezes again. Snow also stays put on a low roof instead of sliding off a steep one. The ground snow load printed in Upper Allen Township's ordinance table is 30 psf, so the deck and framing under the membrane carry real weight in winter.
Summers are humid, and a damp deck under a sealed membrane grows mildew from below. That is why we check the framing and the deck first and the surface second. A flat roof with sound framing, working drains and a clean membrane does its job for a long time. One with soft decking is a replacement job, whatever the surface looks like.
Three membranes cover most flat roofs on houses. Each has its own way of making a seam, and the seam is where most leaks begin.
| Membrane | What it is | How the seams are made |
|---|---|---|
| EPDM | Black synthetic rubber sheet, sold in wide rolls | Seam tape or bonding adhesive, with a primer on the surfaces |
| TPO | White or light-gray single-ply sheet | Hot-air welding, which fuses the two sheets into one |
| Modified bitumen | Asphalt sheets reinforced with a mat, laid in layers | Heat, or a self-adhering backing, lapped and pressed |
EPDM is forgiving on small, oddly shaped roofs and easy to patch. TPO reflects sun, which helps in a humid summer, and its welded seams are strong when the welder keeps the heat and speed right. Modified bitumen holds up under foot traffic, which matters on a roof deck you use.
We pick by the roof, not by habit: its size, its edges, what sits on it, how much shade it gets, and what the framing can carry. The choice goes into the written scope with the reason beside it.
Winter on a flat roof is a drainage problem. Snow piles up, a warm day melts the top layer, and the meltwater runs to a drain or scupper that may still be frozen or packed with leaves. The water then backs up behind the low edge and finds every weak seam and flashing on the way.
Before cold weather we look at three things:
After a heavy snow, do not chip at the roof with a shovel or an ice pick. A cut membrane is a leak you will find in March. Clear the drain, leave the rest to melt, and call us if the ceiling below stains.
In shade, moss and roof algae can grow on a membrane that stays wet. We clean them with products the maker allows, because the wrong cleaner damages the sheet.
EPDM can be repaired well when the rubber around the damage is sound. A homeowner can patch a small cut, but the preparation matters more than the patch.
A patch does not cure a roof that is shrinking, cracking over a wide area or soaked underneath. When the rubber has gone hard and pulls away at the walls, repair after repair costs more than a new membrane, and we say so on the estimate. Our roof repair page explains how we decide.
TPO is repaired by welding, not by gluing. A patch of the same material is fused to the sheet with hot air, so the repair becomes part of the roof instead of a sticker on top of it.
The steps are close to those for rubber, with differences that matter:
Cold, damp days make this work hard to do right, so a repair may wait for a dry window when it is not an emergency. For a leak that cannot wait, we put on a temporary cover and photograph it, then do the permanent repair when the roof is dry.
If the seams are opening in many places, the problem is usually the installation or the age of the sheet, not one bad spot. That is a replacement conversation, and our roof replacement page goes through it.
Pennsylvania has one building code for the whole state. The Uniform Construction Code adopts the 2021 International Residential Code with Pennsylvania's changes, and that version took effect January 1, 2026 under 34 Pa. Code § 403.21. A town may adopt standards that equal or exceed it, but § 403.102 does not let any municipality adopt a lower or different edition. Our state code guide has the detail.
The permit step differs from town to town, so the borough's own rule is the one that counts:
| Town | What its records say |
|---|---|
| Harrisburg | The building permit application lists roofing. Contractors named on it must hold a valid Mercantile License, and the permit is void if no inspection happens within 6 months. |
| Mechanicsburg | Replacing a residential roof covering needs no building permit unless the structure is involved, such as sheathing, rafters or trusses. The owner is responsible for any permit that is required. |
| New Cumberland | Roof replacement is listed among projects that may need a permit. Work may not start until the borough issues it. |
| Camp Hill | The residential fee is $90.00 plus 1.2% of the estimated project value. Third-party review takes between 14 and 30 days, and inspections need 24 hours' notice. |
Where your town asks for a permit, we pull it. Flat roofs often involve the deck underneath, and a soft or replaced deck is the kind of structural work that can change the answer.
We do not print a price here, because a flat roof is priced by the roof in front of us. These are the things that move it:
Our free assessment at the house measures the roof, checks the deck and writes each of these into the estimate. You can also start on our free estimate page.
The first visit is a look at the roof and from inside. We check the ceiling below for stains, test the deck for soft spots, and photograph the membrane, seams, drains and flashing. You keep the photographs whether or not you hire us.
The written scope lists the work line by line: the tear-off, any deck repair, the insulation, the membrane, the flashing at every wall and penetration, and the drains. We ask for a start date only once the scope is agreed.
On the day, our crew covers what needs protecting, removes the old roof, repairs the deck and lays the new system the way the maker's instructions say. We do not leave a tear-off open overnight when rain is coming. Our crew cleans up with a magnet sweep for nails, and we take final photographs of the finished seams and flashing.
After a storm, our storm damage page explains what we inspect and what stays with you and your insurer. Our roof inspection page covers the check itself.
It is when the house shape calls for one, such as an addition, a porch or a row house. It needs working drains, a sound deck and a seam-tight membrane. Our freezing nights and snow make drainage the thing to get right, so we check that before we suggest a membrane.
We find the true source of the leak, clean and dry the rubber, prime it, and press on a rounded patch or seam tape that reaches well past the damage. The edges are rolled tight. If the rubber has hardened or shrunk across the roof, we recommend a new membrane instead.
TPO is fused, not glued. We clean the weathered skin, cut a round patch of the same material, and weld it with hot air and a roller. Then we probe the edge to test the weld. Many open seams usually mean the roof needs replacing.
It depends on your town. Harrisburg's application lists roofing, while Mechanicsburg says a roof-covering replacement needs none unless the structure is involved. Where the town asks for a permit, we pull it, and the scope tells you which case yours is.
Clear the drain or scupper so meltwater can leave, and keep sharp tools off the membrane. Shoveling and chipping cut the sheet. If the ceiling below stains or the roof sags, call us for an inspection before you climb up.
Usually a dip in the deck, a drain set too high, a clogged scupper or a roof that has lost its slope. Standing water wears seams out early. We measure where it collects and write the fix, whether that is drainage or tapered insulation, into the estimate.
Flat roofing across the Harrisburg-Carlisle, Pennsylvania metro. Each city has its own page with the permit rule and code edition that apply there:
Sources: Pennsylvania adopts the 2021 International Residential Code · Municipalities may not adopt a lower or different edition · Upper Allen Township's ground snow load and wind speed table · Harrisburg building permit information · Mechanicsburg roof-covering permit rule · New Cumberland roof replacement permits · Camp Hill building permit fees and review. Codes, programs and prices change; confirm the current rule with your city before you rely on it.
Free inspection, a written scope, and photos you keep either way.
Book my free inspection →