Flat Roof Patch in San Antonio, TX

Flat Roof Patch in San Antonio, TX

A flat roof patch in San Antonio typically costs between $350 and $850 for a standard repair, and most small to mid-sized patches can be completed in a single visit. The final price depends on what the membrane is made of, how large the damaged area is, and whether the underlying decking has rotted. At Mercer Roofing Co San Antonio, we send a technician’s name and photo before they arrive, and you get a written price before any work starts. Call us at (254) 276-4369 to schedule a free estimate.

Flat roofs are everywhere in San Antonio. You see them on mid-century ranches in Jefferson and Monticello Park, on modern builds in Alamo Heights and Stone Oak, and on commercial strip centers up and down Blanco Road. They work well in our climate until they don’t. When a flat roof leaks, water pools and finds its way into places you won’t notice for weeks. That’s why we take a patch seriously: it’s a small repair that prevents a large one. If you’re looking for a Roof Repair in San Antonio team that treats a small patch with the same care as a full replacement, we’re the crew to call.

We’re part of the home services family at Threshold Group, founded in 2000. Every Mercer Roofing technician is background-checked, identity-verified, and arrives in a clean, marked uniform with a photo ID badge. We call that the Threshold Standard, and it means you always know exactly who is walking up your driveway.

When You Need Flat Roof Patch

Flat roofs fail differently than pitched roofs. Instead of shingles lifting or cracking, you get membrane splits, ponding water, and flashing that pulls away from parapet walls. Here are the signs we see most often in San Antonio, especially after our August heat and our occasional hailstorms:

• Water stains on your ceiling or interior walls. With a flat roof, the leak is rarely directly above the stain. Water travels along the decking before it finds a seam to drip through. That’s why we inspect the whole roof surface, not just the obvious spot.
• Ponding water that’s still there 48 hours after rain. Flat roofs are rarely perfectly flat. They’re supposed to have a slight slope toward drains or scuppers. When that slope settles over time, water collects. Standing water accelerates membrane breakdown, which is a common reason Alamo Heights homeowners call us after spring storms.
• Visible cracks, blisters, or alligatoring on the membrane surface. Modified bitumen and rolled roofing surfaces, common on older San Antonio homes, develop cracks after years of UV exposure. Blisters form when moisture gets trapped under the membrane. Both are signs the roof needs patching before a full failure.
• Flashing pulling away from parapet walls or vents. The metal flashing where the flat roof meets vertical surfaces is a frequent leak point. San Antonio’s heat expands and contracts metal, loosening the sealant over several seasons. When the flashing separates, water gets behind the membrane.
• Granule loss from a modified bitumen roof. If you look up and see bare, black spots where the surface coating used to be, the protective top layer is wearing away. That exposed membrane is now vulnerable to UV damage and direct impact from hail.
• Previous patch is failing. Not all patch jobs hold. If a prior company slapped tar or a mismatched membrane over a problem area, the patch can separate within months. Mercer Roofing matches the existing membrane so the repair bonds correctly.

If any of these sound familiar, a Roof Repair services call for a flat roof patch may be the right move, and the sooner it’s done the smaller the bill.

Our Flat Roof Patch Process

We follow a set process on every flat roof patch so there are no surprises on the invoice and no question about who is doing the work.

1. You schedule the estimate. Call (254) 276-4369. A live person answers, 24/7. We ask a few questions about the roof and set a time that works for you.
2. You know who’s coming before they arrive. We send the technician’s name and photo ahead of the visit. When they knock, they’ll be in a clean Mercer uniform with a photo ID badge. Check it against the name we sent.
3. The inspection. The technician examines the damaged area, checks for signs of hidden water damage around the leak, and takes photos. If it’s safe and accessible, they’ll inspect the roof surface directly. If the area looks like it has decking damage underneath, we’ll talk through what that means before any work is proposed.
4. You get a written price. Before any work starts, you receive a written estimate that covers the patch cost, materials, labor, and any disposal. No work begins without your approval, and the number on the estimate is the number on the invoice.
5. The patch work. Our crew cleans the repair area, cuts away the damaged membrane, addresses any wet or rotted decking if approved, and installs a patch using material matched to your existing roof system. For modified bitumen, that means heat-welded or cold-applied material. For TPO or PVC, it means compatible membrane and proper adhesives.
6. You get the written guarantee. Every patch includes our 365-Day Done Right Promise. If the repair fails within a year, Mercer makes it right, and a second visit is free. The guarantee is written, not verbal.

Every step is designed to give you certainty. You know who’s coming, you know what it will cost, and you have the repair in writing.

Flat Roof Patch Pricing in San Antonio

Here’s How Much Does Roof Repair Cost? (2026 Price Guide) - San Antonio, TX for a flat roof patch based on the work involved. These are honest ranges, not teaser prices that balloon once a crew is on the roof.

Repair Type	Typical Cost Range	What’s Included
Small puncture or blister repair (under 10 sq ft)	$350 – $500	Surface prep, membrane patch, sealant, cleanup
Flashing reseal at vent or pipe boot	$250 – $400	Removal of old sealant, new flashing or sealant, water test
Mid-size patch (10 – 25 sq ft) with ponding correction	$500 – $850	Membrane repair, minor slope correction, surface coating
Parapet wall cracking repair	$450 – $700	Crack sealing, membrane patch at wall junction, flashing re-adhesion
Decking replacement (if water damage is found)	$150 – $300 per sheet	Rotted wood removal, new decking, membrane tie-in

Several things move the price one direction or another. The type of membrane matters: TPO and PVC patch materials cost more than modified bitumen, but they’re what you need if your roof is a single-ply system. Roof accessibility plays a role too; a second-story flat roof with limited access takes more time to set up safely. The biggest unknown is always what’s underneath. We won’t know if the decking is rotted until we open the membrane, but we’ll tell you what we find and get your approval before any extra work proceeds.

Mercer Roofing does not charge for estimates. You’ll get a written price before any work starts. Call (254) 276-4369 to schedule yours.

The Materials We Use for Flat Roof Patches

The key to a lasting flat roof patch is matching the membrane. Patching a TPO roof with modified bitumen is a shortcut that fails quickly because the materials expand and contract at different rates in Texas heat. We use the right material for your existing roof system.

Modified Bitumen

Common on older San Antonio homes, modified bitumen is an asphalt-based membrane that comes in rolls. We patch it with heat-welded or cold-applied material so the repair bonds into the existing surface. When the top coating has granule loss, we include a UV-protective coating so the patch doesn’t become the next weak spot.

TPO and PVC

These white, reflective single-ply membranes are common on newer builds and commercial roofs in San Antonio. We patch them with compatible material from manufacturers like GAF, CertainTeed, and Owens Corning. The adhesives and welding methods differ from modified bitumen, and using the right system is what keeps a TPO patch watertight for years.

Built-Up Roofs (BUR)

Older built-up roofs, with alternating layers of tar and gravel, need careful patching that respects the existing layers. We cut back the damaged section, replace the deteriorated plies, and re-seal the surface to match the original system.

For homes with shingle sections adjacent to flat roof areas, we also work with manufacturer-recognized shingle brands including GAF and CertainTeed when tie-ins are needed.

Why San Antonio Homeowners Choose Mercer Roofing

There are a lot of roofing companies in San Antonio. Here’s what Mercer Roofing does differently, in plain terms.

• You know who’s coming. Every technician is background-checked, identity-verified, and we send their name and photo before they arrive. They wear a photo ID badge at your door. If the person who shows up doesn’t match the photo we sent, you don’t have to open the door. That’s the Threshold Standard.
• Written price before work starts. Always. No exceptions. You approve the number before a single tool touches your roof.
• 365-Day Done Right Promise. If your flat roof patch fails within a year, we fix it at no charge. The guarantee is written and included with every repair, and it includes a free second visit if the repair fails.
• A live person answers the phone. Call at 2 a.m. during a storm, and a real human at Mercer Roofing picks up. Not a voicemail. Not a callback form. We’ve been answering this way since we joined the Threshold Group family, founded in 2000.
• We don’t upsell replacements when a patch works. If your flat roof only needs a patch, we’ll tell you that. If a larger repair or replacement makes more financial sense, we’ll show you the numbers and let you decide.

Grant Whitlock leads our San Antonio team with one standing rule: treat every roof as if it were on his own home. That rule shapes everything from the way our technicians introduce themselves to the way we leave your property when the job is done.

Flat Roof Patch vs. Replacement: How to Decide

This is the question every homeowner should ask, and the answer depends on the roof’s overall condition. A patch makes sense when the damage is isolated: one puncture, one section of failing flashing, one area of ponding that hasn’t yet compromised the decking. If the rest of the membrane is sound, a patch can add several years to the roof’s life at a fraction of replacement cost.

Replacement becomes the honest recommendation when the membrane is brittle across large areas, when decking has rotted in multiple places, or when the roof has been patched repeatedly and previous repairs are separating. We’ll show you photos of what we find and give you a straight comparison: what a patch will cost now, and what continued patching will likely cost over the next five years. The decision is always yours, and you’ll never be pressured into a replacement you don’t need.

FAQs – Flat Roof Patch

How much does a flat roof patch cost in San Antonio?

A flat roof patch in San Antonio typically runs between $350 and $850, with smaller punctures and flashing reseals landing at the lower end and mid-size patches with ponding correction at the upper end. Decking replacement, if needed, adds $150 to $300 per sheet. Call (254) 276-4369 for a free, written estimate that covers your specific roof.

Can you patch a flat roof the same day?

Yes, in most cases a flat roof patch can be completed the same day, especially if the membrane is accessible and there’s no hidden decking damage. We’ll confirm timing when you call, and we’ll give you a written price before any work begins.

How long does a flat roof patch last?

A properly matched flat roof patch can last 5 to 10 years when the surrounding membrane is in good condition. Mercer Roofing backs every patch with our 365-Day Done Right Promise, which covers a free second visit if the repair fails within a year.

Do you patch flat commercial roofs in San Antonio?

Yes, we patch flat roofs on both homes and small commercial buildings throughout San Antonio, including properties in Alamo Heights, Terrell Hills, Stone Oak, and downtown, for anyone searching Roof Repair Near Me in San Antonio, TX. The materials and process are the same approach: match the membrane, prep the surface, and provide a written guarantee.

Is it cheaper to patch or replace a flat roof?

Patching is always cheaper in the short term, typically $350 to $850 versus $8,000 to $15,000 for a full flat roof replacement in San Antonio. If the roof has multiple failing areas or widespread membrane deterioration, replacement can be the more cost-effective choice over five years. We’ll show you the numbers for both options during a free estimate so you can decide with real information.

Call Mercer Roofing Co San Antonio for Flat Roof Patch

If you’ve got a leak, a crack, or just a feeling that your flat roof isn’t quite right, call us at (254) 276-4369. A live person answers. You’ll get a written price before any work starts, and you’ll know exactly who is coming to your door before they get there. Grant Whitlock and the Mercer Roofing team serve San Antonio homeowners and businesses with flat roof patches that are done right, guaranteed in writing, and backed by the Threshold Standard.

Written by Grant Whitlock, Owner at Mercer Roofing Co San Antonio, serving San Antonio.