Flat Roofing

Flat Roofing That Drains Right

Flat roofing is not truly flat — every low-slope roof has a slight pitch to move water toward drains and scuppers. The challenge is that water moves slowly on a low slope, so the roofing system must be continuously waterproof, fully adhered, and detailed carefully at every penetration, edge, and drain. A flat roof that drains well and is maintained properly can last 20 to 35 years; one that drains poorly will leak within a few seasons.

We install and repair flat roofing on commercial buildings, apartment complexes, garages, home additions, and modern residential homes with low-slope sections. Our crews work with TPO, EPDM, modified bitumen, and built-up roofing — choosing the system that matches the building’s use, climate, and budget.

Flat Roofing Systems Compared

Each flat roofing material has different strengths. The right choice depends on the building.

System	Material	Lifespan	Cost per square	Best for
TPO	Thermoplastic polyolefin	20 – 30 years	$500 – $900	Energy efficiency, commercial
EPDM	Synthetic rubber	25 – 35 years	$450 – $800	Flexibility, residential low-slope
Modified bitumen	Asphalt with modifiers	15 – 25 years	$400 – $700	Walkways, high-traffic roofs
Built-up (BUR)	Multiple asphalt layers	20 – 30 years	$500 – $900	Heavy-duty commercial
PVC	Polyvinyl chloride	25 – 35 years	$600 – $1,100	Restaurants, chemical exposure

TPO has become the most popular choice for new flat-roof installations. Its white reflective surface reduces cooling costs, the seams are heat-welded for a permanent bond, and the material resists UV degradation, punctures, and chemical damage.

How We Install a Flat Roof

Low-slope roofing demands meticulous preparation and detailing. There is no room for shortcuts when water does not shed quickly.

1. Deck inspection — we check the substrate for rot, delamination, and proper slope; add tapered insulation if the roof does not drain adequately
2. Old roofing removal — we strip existing layers down to the deck for a clean start; no layering over compromised material
3. Moisture barrier — self-adhering membrane or base sheet applied across the deck
4. Insulation — rigid foam insulation boards laid to build slope and improve energy performance
5. Membrane installation — TPO or EPDM laid out, seams heat-welded or adhered, edges secured with termination bars
6. Flashing and detailing — curbs, walls, skylights, pipes, and drains detailed with matching membrane and sealant
7. Drain and scupper installation — new drains where needed, scuppers cut and flashed properly
8. Walkway pads — placed at high-traffic areas like HVAC units and roof hatches to protect the membrane

Flat Roofing Costs

The total cost depends on membrane type, roof size, insulation requirements, and how many penetrations need detailing.

Component	Typical range
TPO membrane system	$5,000 – $15,000
EPDM membrane system	$4,500 – $12,000
Modified bitumen system	$4,000 – $10,000
Tapered insulation (per inch)	$1.50 – $3.00 per sq ft
Drain and scupper work	$500 – $2,000 per unit
Tear-off of existing layers	$1,000 – $3,000

Commercial flat-roof projects often include rooftop HVAC support, walkway pads, and parapet wall flashing — we price these as line items so you see exactly what you are paying for.

Flat Roof Maintenance

Flat roofs need more maintenance than steep-slope roofs because water and debris sit on the surface longer.

• Inspect after every rain — check for ponding water that does not drain within 48 hours
• Clear drains, scuppers, and gutters of leaves and debris before each season
• Walk the roof quarterly to check for punctures, loose seams, or bubbling membrane
• Repair any damage immediately — small punctures on a flat roof become big leaks fast
• Schedule a professional inspection annually
• Keep HVAC equipment pads clean and check that vibration does not damage the membrane

Common Flat Roof Problems

Understanding what goes wrong helps you prevent it.

• Ponding water — standing water for more than 48 hours accelerates membrane degradation; usually caused by poor slope or clogged drains
• Seam failure — heat-welded or adhesive seams that separate allow water intrusion
• Puncture damage — foot traffic, dropped tools, or falling branches damage the membrane surface
• Flashing detachment — edges and curbs where the membrane meets a wall or equipment curb can pull away over time
• UV degradation — prolonged sun exposure breaks down the membrane surface, especially on darker-colored roofs

Have a flat roof that is leaking or nearing the end of its life? Call us or request a free inspection online — we will assess the membrane, check drainage, and recommend the right system.

Flat Roof Drainage Design

Proper drainage is the most important factor in flat-roof performance. A flat roof without adequate drainage will leak regardless of the membrane quality.

Drainage type	How it works	Best for
Internal drains	Roof drains connected to building’s downspout system	Large commercial roofs, multi-story buildings
Scuppers	Openings in the parapet wall that drain to exterior downspouts	Smaller buildings, residential low-slope
Gutters	External gutters at the roof edge	Residential flat roofs, additions
Tapered insulation	Sloped insulation that directs water to drains or scuppers	Any flat roof with poor original slope

We design drainage systems that move water off the roof within 48 hours. Ponding water for more than 48 hours degrades every membrane type and voids most warranties. If your flat roof has standing water after rain, the drainage system needs evaluation — it may need re-sloping with tapered insulation, additional drains, or scupper upgrades.

Flat Roof Inspection Checklist

During a flat-roof inspection, we evaluate every component of the roofing system:

1. Membrane condition — cracks, blisters, punctures, seam integrity, UV degradation
2. Drainage — ponding water, drain flow, scupper function, gutter condition
3. Flashing — wall transitions, equipment curbs, skylight edges, pipe penetrations
4. Parapet walls — cap condition, sealant joints, weep holes
5. Rooftop equipment — HVAC units, exhaust fans, solar panels — vibration damage, sealant condition
6. Insulation — moisture detection via infrared scan, compression damage from foot traffic
7. Structural — deck deflection, sagging areas, evidence of structural movement

A comprehensive inspection catches problems early and gives you a clear picture of the remaining roof life. We provide a written report with photos and prioritized repair recommendations.

Flat Roof Warranties

Warranty type	What it covers	Typical term
Material warranty	Membrane defects and premature failure	15 – 30 years
Workmanship warranty	Installation quality and labor	5 – 15 years
System warranty	Material + labor as an integrated system	20 – 30 years
NDL (no dollar limit) warranty	Full replacement cost without cap	20 – 30 years

System and NDL warranties require the contractor to be certified by the membrane manufacturer. We hold certifications from major flat-roof membrane manufacturers, which allows us to offer extended warranty coverage that uncertified contractors cannot.