Flat Roof Repair Methods Used on Low Slope Homes in New Orleans

No flat roof is actually flat. Every one of them is built to drain, and most low slope roofing problems trace back to the point where that drainage stopped working.

That’s why a flat roof repair looks nothing like patching shingles. You’re fixing a continuous waterproof membrane, its seams and its terminations, and the method depends entirely on which membrane is up there. Our flat roof page covers the systems we work on, and the TurnKey Roofers homepage has the rest.

If yours is leaking now, call (504) 732-0336 or send photos through the contact page.

Key takeaways

• Identify the membrane first. EPDM, TPO, PVC, modified bitumen and built up all repair differently.
• Most leaks are at seams, terminations, penetrations and drains, not in the open field of the membrane.
• Water standing longer than 48 hours after rain is ponding, and it’s a defect rather than a quirk.
• Model codes require a minimum 1/4 inch per foot slope on new low slope roofs and positive drainage on reroofs.
• Flat, rolled and single ply repairs run $200 to $500 for minor work and $250 to $1,000 per square.
• A wet low slope assembly usually needs an infrared scan, at $400 to $600, before anyone can scope the repair.

Know what you’re standing on

The membrane sets the repair method, the materials and the price. These are the systems you’ll find on New Orleans houses and small commercial buildings.

HomeGuide notes that TPO, built up and PVC suit hot climates, while EPDM and modified bitumen do better in cold ones. That’s worth knowing before anyone recommends a full replacement in a material that isn’t matched to a Gulf Coast summer.

Where low slope roofs actually fail

A Carlisle SynTec field service representative with 25 years of rooftop inspections lists the defects he finds most often on EPDM. Every one of them is at a joint or an edge rather than in the middle of a sheet.

• Fishmouths in field seams. A wrinkle at the seam edge that opens a channel, commonly at deck flange splices on curb and wall flashings.
• Missing lap sealant. The cut edges of reinforced membrane and uncured flashing need sealant, and it gets skipped.
• Loose or missing drain bolts. The clamping ring is what holds the membrane into the drain, and a loose one leaks straight into the building.
• Membrane cut too tight at the drain. The hole has to be cut larger than the drain pipe diameter, not fitted to it.
• Incomplete edge metal. Carlisle’s representative calls edge metal one of the most critical parts of the system, because many uplift failures start at the roof edge.

Add mechanical damage to that list. Foot traffic around rooftop equipment, dropped tools and storm debris all puncture membrane, and on a ballasted or gravel surface the puncture can hide under the surfacing for a long time.

How each system gets repaired

The principle is the same across all of them: clean the area, prepare the surface as the manufacturer requires, and bond compatible material over it. The technique differs by chemistry.

Two rules apply to all of them. Use material from the same family as the existing membrane, since a TPO patch won’t bond to EPDM. And repair to the manufacturer’s written method, because the code requires roof assemblies to be installed in accordance with the approved manufacturer’s instructions.

Ponding water is a defect, not a feature

The Asphalt Roofing Manufacturers Association defines ponding water as water that remains on a roof 48 hours or longer. Short term puddling after heavy rain is normal. Water that’s still there two days later is not.

ARMA lists what ponding does: it increases the load on the deck, which increases deflection, which collects more water. It grows algae and vegetation that damage the membrane and clog drains. It accumulates dirt and debris that degrade the surface.

ARMA recommends a minimum slope of 1/4 inch per foot so a roof drains freely, and notes that model building codes require that same minimum on new construction and positive drainage on reroofing projects. Where the deck itself can’t provide that, a tapered insulation system builds the slope above it, with crickets upslope of rooftop equipment and saddles between drains.

Drains, scuppers and the overflow nobody checks

Louisiana’s 2021 International Residential Code requires roof drains at each low point where the roof isn’t sloped to drain over its edges. That’s the easy part.

The part people miss is secondary drainage. Where the roof perimeter is built up in a way that traps water if the primary drains block, the code requires overflow drains or scuppers. Overflow drains match the primary drain size with the inlet flow line 2 inches above the low point, or scuppers three times the drain size with a minimum opening height of 4 inches, set at the same 2 inch height in the adjacent parapet.

Clearing debris off a low slope roof is the cheapest maintenance there is. A blocked drain turns a rainstorm into a structural load, and the overflow is the only thing standing between that and the ceiling below.

What low slope repairs cost

HomeGuide puts flat, rolled and single ply repairs at $200 to $500 for minor work and $250 to $1,000 per square, which is 100 square feet. Larger numbers come from what’s underneath rather than the membrane itself.

• Replacing wet insulation runs $100 to $450 per 100 square feet.
• Roof deck repair runs $200 to $500 per 100 square feet.
• Flashing repair runs $200 to $500, and replacing and resealing all flashing $400 to $1,000.
• A roof drain costs $70 to $340 installed.
• An infrared inspection to map trapped moisture runs $400 to $600.
• Full replacement runs $3 to $11 per square foot, or $4,000 to $16,800 for a typical roof.

The infrared scan is the one people skip and shouldn’t. Patching the membrane over saturated insulation seals the water in, and the deck underneath keeps deteriorating with no visible symptom until it sags. Our residential roof repair page and commercial roof repair page both cover that assessment step.

Repair, coat or replace

Three options sit on the table once a low slope roof starts giving trouble, and the deciding factor is usually how much water is already inside the assembly.

1. Repair when the damage is local, the insulation under it is dry, and the membrane still has years left. This is patching seams, terminations and punctures.
2. Coat when the membrane is sound but tired. The code permits a new protective roof coating over an existing coating as a recover rather than a replacement, so it avoids a tear off.
3. Replace when the insulation is saturated across a large area, the deck is deteriorating, or the membrane has reached the end of its service life.

A coating won’t rescue wet insulation. It seals the top, and everything under it stays wet, which is why the moisture survey comes before the decision rather than after it.

Staying off a wet membrane

Low slope roofs feel safe because they’re close to level, which is exactly what makes people careless on them. A wet single ply membrane is genuinely slick, and the edge has no shingle line to warn you where it is.

OSHA requires fall protection for construction work at six feet and above, which covers most residential low slope roofs. Leave the inspection and the repair to someone with the right anchorage, and do your own looking from a window, a neighboring building or the ground.

Frequently asked questions

How much does it cost to have a flat roof repaired?

Minor single ply and rolled roofing repairs run $200 to $500, and larger sectional work runs $250 to $1,000 per 100 square feet. Costs climb once wet insulation or decking is involved, at $100 to $450 and $200 to $500 per 100 square feet respectively. Most roofers also apply a $150 to $300 minimum fee for the visit.

What is best to repair a flat roof?

Material that matches what’s already there, installed the way its manufacturer specifies. A TPO or PVC roof gets a hot air welded patch of the same membrane, EPDM gets a primed and bonded EPDM patch with lap sealant at the cut edges, and modified bitumen gets a torched or self adhered cap sheet patch. Universal sealants and roof cement smeared over a seam are a short term measure at best.

What is the cheapest way to cover a flat roof?

Rolled asphalt is the lowest cost option at $2.00 to $5.00 per square foot installed, and it also has the shortest life of any flat roof material. Built up tar and gravel at $3.50 to $7.50 and fiberglass at the same range sit slightly above it with far better longevity. On a roof you plan to keep, the cheapest material per square foot rarely stays the cheapest per year.

Why does my flat roof leak only in heavy rain?

Because the drainage is marginal and the rain is outrunning it. Water backs up behind a blocked drain or a low spot, rises above a flashing termination or a seam edge, and finds a path that a normal shower never reaches. That points at drains, scuppers and terminations rather than at the field of the membrane.

Get the membrane identified and the leak found

Half the bad flat roof repairs we see are the right technique applied to the wrong membrane. Identify the system, find the actual entry point, and the fix tends to be small.

We’ll do both and quote it in writing. Call (504) 732-0336 or use the contact page.

Related reading

• How to Identify and Fix Common Roof Leaks
• How to Manage a Roof Upgrade Without Interrupting Your Tenants
• How Weather Affects Your Roof and What You Can Do About It

Sources

• HomeGuide, Flat Roof Replacement Cost (2026)
• HomeGuide, Roof Repair Cost (2026)
• HomeGuide, Roof Inspection Cost (2026)
• ARMA, Ponding Water Basics: Proper Drainage Design and Low-Slope Roofs
• Carlisle SynTec, Voice of an FSR: Inspecting EPDM Roofs
• Louisiana Residential Code 2021, Chapter 9 Roof Assemblies
• OSHA, Fall Protection Overview