Roofing cost · Roof Replacement
Flat Roof Replacement Cost
The answer: Replacing a residential flat roof costs $3 to $11 per square foot installed, or $4,000 to $16,800 on average, according to HomeGuide. EPDM rubber and built-up roofs sit at the low end, while PVC costs the most. Tear-off adds $1 to $2 per square foot. Repairing a flat roof costs $300 to $1,100 on average.
| Flat roof replacement | $4,000–$16,800 |
|---|---|
| Sources checked | 3 |
Flat and low-slope roofs use membranes or layered coatings instead of shingles. HomeGuide puts residential replacement at $3 to $11 per square foot installed, or $4,000 to $16,800 on average.
Cost by material
| Material | Per sq ft installed | Total installed |
|---|---|---|
| Built-up (tar and gravel) | $3.50 – $7.50 | $4,500 – $12,600 |
| EPDM (rubber) | $3.50 – $10.00 | $6,200 – $16,000 |
| Spray foam | $3.50 – $7.00 | – |
| Modified bitumen | $4.00 – $7.50 | $4,900 – $14,600 |
| TPO | $4.00 – $10.00 | $7,700 – $14,000 |
| PVC | $5.00 – $12.00 | – |
Source: HomeGuide.
EPDM is a rubber membrane. TPO and PVC are single-ply membranes. Modified bitumen is rolled asphalt, and built-up roofs layer tar and felt topped with gravel.
Tear-off and other costs
HomeGuide lists tear-off of a flat roof at $1 to $2 per square foot, including disposal. New decking, if the old one is rotted, costs $2 to $5 per square foot (HomeGuide roof replacement guide).
Repair instead
HomeGuide puts flat roof repair at $2.50 to $10.00 per square foot, or $300 to $1,100 on average. Angi's average repair cost for a flat, foam or single-ply roof is $400.
See roof repair cost and roof replacement cost.
Cost by roof size
| Size | Cost (HomeGuide) |
|---|---|
| 800 sq ft | $2,400 – $8,800 |
| 1,000 sq ft | $3,000 – $11,000 |
| 1,500 sq ft | $4,500 – $16,500 |
| 2,000 sq ft | $6,000 – $22,000 |
| 3,000 sq ft | $9,000 – $33,000 |
HomeGuide's national average is $10,800. Labor runs $2.00 to $4.50 per sq ft.
Garage flat roofs
| Garage | Cost (HomeGuide) |
|---|---|
| 1-car | $850 – $3,100 |
| 2-car | $1,200 – $4,400 |
| 3-car | $2,500 – $9,200 |
Other materials (installed per sq ft)
Rolled asphalt $2.00 – $5.00, fiberglass $3.50 – $7.50, metal $5.00 – $16.00, concrete $4.00 – $15.00.
Add-ons
| Item | Cost (HomeGuide) |
|---|---|
| Insulation, polyiso boards | $0.50 – $3.00 per sq ft |
| Insulation, spray foam | $1.50 – $5.00 per sq ft |
| Roof coating | $1 – $4 per sq ft |
| Roof drain | $70 – $340 |
| Roof vent | $200 – $700 |
| Permit | $150 – $500 |
Converting to a pitched roof costs $9,000 to $37,500 for framing alone (HomeGuide).
Common flat roof materials
- TPO: a white or light single-ply membrane, often heat-welded at the seams.
- EPDM: a rubber membrane, usually black, glued or ballasted in place.
- Modified bitumen: rolled asphalt sheets, applied with torch, cold adhesive or self-adhesive.
- Built-up roofing (BUR): layers of asphalt and felt with a gravel top.
- Coatings: liquid-applied coatings that can extend the life of some existing roofs.
Why flat roofs leak
Flat roofs are not perfectly flat; they need a slight slope to drain. Problems start when water ponds on the surface, seams open up, or flashing at walls and roof edges fails. Drains and scuppers clogged with leaves are a common cause of standing water.
What affects the price
- Roof size and material.
- Insulation added under the new membrane.
- Removing the old roof and replacing wet insulation or decking.
- Drains, edges, curbs and rooftop equipment.
- Access to the roof.
Replace or coat?
A coating can buy time on a roof that is still dry underneath. If the insulation or deck is wet, or the roof is near the end of its life, replacement is the better choice.
Questions to ask
- Will you check for wet insulation before quoting?
- How will you improve drainage?
- What does the warranty cover: materials, labor or both?
In Texas
Strong sun and heat are hard on flat roofs. Light-colored membranes, such as white TPO, reflect sunlight and can reduce heat gain in hot Texas summers.
Comparing flat roof materials
TPO is a single-ply white membrane that reflects sunlight, which helps keep buildings cooler. Seams are heat-welded. It is a popular choice for homes and commercial buildings.
EPDM is a black rubber membrane known for durability and flexibility. Seams are glued or taped. It absorbs heat, though white versions exist.
PVC is a single-ply membrane with heat-welded seams that resists chemicals, grease and fire. It costs more than TPO.
Modified bitumen is an asphalt-based roll roofing applied with heat, adhesive or self-adhering backing. It is tough and easy to repair.
Built-up roofing (BUR) uses layers of asphalt and felt topped with gravel. It is durable but heavy and less common on homes today.
Coatings like silicone and acrylic can be applied over some existing roofs to extend their life, if the roof is in good condition.
Ponding water
Flat roofs are not completely flat. They should slope slightly to drains, scuppers or gutters. Water that stays on the roof for more than a couple of days after rain, called ponding, can break down the membrane, add weight and find its way through small defects. Fixing slope problems with tapered insulation or additional drains is often part of a replacement.
Insulation
Flat roof replacement is a good time to add insulation on top of the deck. Rigid insulation boards improve energy efficiency, and tapered boards can correct slope at the same time. Energy codes may require a minimum insulation level when a roof is replaced.
Maintaining a flat roof
Inspect the roof twice a year and after storms. Keep drains and scuppers clear of leaves and debris, check seams and flashing around equipment and walls, and look for blisters, cracks and punctures. Limit foot traffic on the roof, since walking can damage some membranes.
Choosing a flat roof contractor
Flat roofing is a specialty. Ask whether the contractor is certified by the membrane manufacturer, how many flat roofs they install each year and whether they offer a manufacturer warranty. Ask how they will handle drainage, insulation and flashing at walls and equipment.
Many residential flat roofs are replaced in a day or two. Larger roofs and those needing insulation or drainage changes take longer.
Equipment on the roof
Air conditioners, vents and skylights on flat roofs need careful flashing. Equipment may need to be lifted during replacement, which can add cost. Walkway pads around equipment protect the membrane from service traffic. Ask whether the new roof will include tapered insulation where water now ponds. Tapered boards slope water toward drains and often solve ponding for good. Ask also whether the drains, scuppers and overflow outlets will be replaced or resized, since undersized drains are a common reason water sits on flat roofs after storms.
Sources
Roofing contractors in Texas
Our Texas business directory lists 1,413 roofing contractors across 6 major cities. The ratings below are the average Google rating of the listed businesses in each city, and the review counts are the total number of Google reviews they have received.
| City | Businesses listed | Avg. Google rating | Total reviews |
|---|---|---|---|
| Houston | 458 | 4.8 | 30,851 |
| Dallas | 221 | 4.6 | 16,129 |
| San Antonio | 249 | 4.6 | 22,474 |
| Austin | 200 | 4.8 | 17,830 |
| Fort Worth | 189 | 4.8 | 11,127 |
| El Paso | 96 | 4.4 | 4,730 |
Source: twupro Texas business directory, built from public Google Maps listings.
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