Flat Roof Repair in Texas: Built-Up, Tar-and-Gravel, and Mod-Bit

If there is water on the ceiling below your flat section today, you are in the right place. The first thing to know about residential flat roofs is that most flat-roof leaks are a repair, not a replacement. A single soft spot, an open seam, or a tired flashing detail can let water in without meaning the whole roof has failed.

Get a bucket under the drip, pull anything valuable out from underneath, and photograph the stain before it spreads. Then let us trace it. On a built-up or modified-bitumen roof, the spot where water shows up inside is almost never the spot where it got in, so chasing the stain with a tube of sealant usually buys a few dry weeks and nothing more.

A flat roof does not shed water the way a pitched roof does. It holds it, moves it slowly to drains, and relies on a continuous membrane to stay watertight. That means the failure points are different: laps that opened as the asphalt aged, a blister that finally split, gravel that migrated and left a bare spot, or flashing at a wall or drain that pulled loose. Texas heat drives all of it, cycling the membrane hot and cold until the weakest detail gives up.

We keep the full catalog of what goes wrong on these roofs on the flat roof problems page. On this page the point is narrower: how we find the actual leak and match it to the right fix, so you pay for the repair the roof needs and not the one that is easiest to sell.

Most of the failures I've scoped after storms weren't storm damage. They were install failures that showed up two, three, five years later. That's the difference between a roof that was sold to you and a roof that was installed for you.

Once the leak is traced, almost every residential flat roof lands in one of five repairs. Here is what each one is, when it is the right call, and roughly what it runs.

Every one of these prices is a flat job total for the fix itself. A mod-bit cap-sheet patch is $150 to $1,500 whether your roof is 400 square feet or 4,000, because you are paying for the repair, not the roof. Ponding correction and coating restoration are the two that scale with area, and we quote both from the actual measured roof after inspection.

Updated July 2026, Texas residential flat and low-slope pricing. Ranges assume normal access and a membrane that is otherwise sound; hidden saturation found on inspection can move the number.

Cap-sheet patch. We cut back to sound material, prime the exposed asphalt, and set a new modified-bitumen cap sheet in matching adhesive with the laps rolled and sealed. On a granulated roof we finish so the patch sheds and drains like the field around it.

Seam and lap re-seal. Open laps get cleaned, re-adhered, and sealed along the full run, not just at the wet end. A seam that opened once will open again a foot down the line, so we re-seal the whole lap rather than dab the drip.

Flashing at walls and penetrations. This is where most flat roofs actually leak. We strip the failed flashing at the wall base, curb, drain, or pipe boot, rebuild the detail with new membrane and metal where it belongs, and tie it back into the field so water cannot track behind it.

Ponding correction. Standing water is a symptom of a low spot or a blocked path to the drain. We build the low area back up with tapered material so water moves off the roof instead of sitting on it and cooking the membrane.

Coating restoration. When the membrane is still watertight but sun-worn, a compatible restoration coating over a cleaned, sound roof adds years without a tear-off. We only recommend this when the roof underneath earns it, and we say so in writing when it does not.

The install crew we deploy and supervise does the work, and an ARP project manager inspects the detail before we call it done. You get before-and-after photos of the repair either way.

A well-made flat-roof repair on a membrane that still has life in it typically buys several more service years, and a coating restoration over a sound roof can add more. What a repair cannot do is outrun a membrane that has already failed end to end. When the field is saturated, the laps are opening faster than we can seal them, and water is standing over half the roof, patching becomes throwing good money after bad.

That is the honest line between repair and replacement. If your roof is past it, a full built-up or modified-bitumen replacement runs $6.00 to $8.00 per square foot of roof area, and that number is sized to your measured roof, not to any repair above. We walk through the full replacement math, market by market, on the flat roof cost page. For a leak or a few problem spots, though, start with a repair and a written inspection. You can always spend the replacement money later. You cannot get it back once it is spent.

Most Texas homes with a flat or low-slope section carry one of three systems, and knowing which you have tells you what a repair involves.

• Built-up roof (BUR), or tar-and-gravel. Layers of asphalt and reinforcing felt topped with a gravel surface. Repairs mean clearing the gravel back to the failure, patching the built-up plies, and re-graveling so the fix drains like the field around it. These are the roofs where migrated gravel and open laps drive most leaks.
• Modified bitumen (mod-bit). A rolled asphalt membrane with a granulated cap sheet. Think of it as built-up's modern cousin. It patches cleanly with a matching cap sheet set in adhesive, which is why a small mod-bit patch is the most affordable fix on the table above.
• Coated or restored membrane. Any of the above with a reflective coating over it. If the coating and the membrane below are sound, we spot-repair and re-coat so the surface stays continuous.

We repair all three. The one flat roof we do not cover here is a commercial single-ply system (TPO, PVC, or EPDM), which is a different crew and a different page. If you are not sure what is on your roof, the inspection identifies it before anyone quotes a repair.

We would rather tell you before the inspection than after.

We're a great fit if:

• Your flat or low-slope roof has a specific leak or a few problem spots, not whole-roof failure
• You have a built-up, tar-and-gravel, or modified-bitumen roof
• You want the leak traced and documented, not just sealed over
• Your membrane still has life left and you want to extend it with the right repair or a coating

We might not be the right fit if:

• Your membrane is saturated across the whole roof and holding water everywhere, which means a replacement, and the cost page is the honest next step
• You want the cheapest caulk-tube patch with no inspection and no photos
• You own a commercial building with a single-ply system, which is a different crew and a different page

The cheapest time to fix a flat roof is before the water reaches the decking. Book a free inspection and we will trace the leak, show you the detail that failed, and give you a flat-priced repair in writing.

Schedule Your Free Flat-Roof Inspection →