Low-slope & flat roof systems
Flat roof installation contractor in Austin — because flat roofs fail at the drainage
Hiring a flat roof installation contractor in Austin is mostly a decision about water movement. Membranes rarely fail because the material was wrong. They fail because water sat somewhere it should not have, for longer than it should have, season after season, until the seam or the flashing gave up. Slope and drainage are the job.
- Tapered insulation designed to move water, not just fill space
- Drain and scupper capacity checked against the roof area they serve
- Crickets behind every curb wide enough to dam water
- Ponding corrected during installation, not noted and left
SERVING AUSTIN SINCE 2008 · 500+ COMMERCIAL PROPERTIES
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Free flat roof inspection
We check slope, drain placement and capacity, ponding areas and where water is actually going — then send a written report with photographs and a planning range. One visit, no obligation.
THAN THIS IS PONDING
IS ACTUALLY FLAT
PER SQUARE FOOT
INSPECTION
The thing the name gets wrong
No commercial flat roof is actually flat
A properly built low-slope roof is pitched — typically a quarter inch of fall per foot of run — toward drains or scuppers. It reads as flat from the parking lot and it is anything but at the deck. When someone says a building has a flat roof, what they usually mean is that it has a roof whose slope you cannot see, and sometimes what they actually mean is that the slope was never built.
SCHEMATIC — NOT TO SCALE. Slope is achieved with tapered insulation, a sloped structural deck, or both.
Where a dead-flat deck cannot be re-pitched structurally, tapered insulation builds the fall into the assembly above it.
This matters more in Austin than the annual rainfall figure suggests, because our rain does not arrive politely spread across the year. It arrives in short, violent downpours that dump more water in an hour than a marginally sized drain can move — and then the sun comes out and bakes whatever is left standing. A roof that copes with a steady drizzle can fail on the first genuine Central Texas storm.
The failure mode
What standing water actually does to a roof
The working definition used across the industry is straightforward: water still standing forty-eight hours after rain stops, in weather that should have dried it, is ponding. Not a puddle. A defect. Here is why it is treated that way rather than tolerated.
Weight the deck was not designed for
Water weighs a bit over five pounds per square foot per inch of depth. A two-inch pond across a thousand square feet is more than ten thousand pounds of live load sitting in one place. Deflection makes the low spot lower, which collects more water, which deflects further.
Accelerated membrane aging
Constant saturation degrades membranes and adhesives faster than dry exposure does, and it concentrates the damage exactly where seams and laps sit. The rest of the roof can be in fine condition while the ponded area is finished.
Any breach becomes a reservoir
A pinhole on a sloped area sheds most water past it. The same pinhole under standing water is fed continuously, which is how a defect the size of a pencil tip saturates a wide area of insulation.
It can void the warranty
Many manufacturer warranties exclude damage caused by ponding water. So the roof most likely to fail early is also the roof least likely to be covered when it does — which is why correcting slope during installation is not an upsell.
Show a contractor the standing-water marks on your roof — the dark rings, the dirt lines, the algae — and ask a single question: "what are you doing about that?"
An answer about the new membrane being more durable is the wrong answer. The right answer involves tapered insulation, a relocated or added drain, or a cricket — something that changes where the water goes. A new membrane over an uncorrected low spot is a new membrane that will fail in the same place.
The installation
How we build slope into a flat roof
As commercial roofers in Austin TX working almost entirely on low-slope buildings, this is the sequence on every flat roof we install.
Map where water actually goes
Before any design work, we find the low spots — from staining, debris lines and where ponding marks sit relative to the drains. On an existing roof this is visible evidence, and it frequently shows that a drain was placed where the plans said rather than where the deck actually falls.
Check drain capacity against roof area
Drains and scuppers are sized for the area they serve and the rainfall intensity they have to handle. Undersized or too few is one of the most common inherited problems on older Austin buildings, and no membrane compensates for it. Overflow provision matters too — when a primary drain blocks, water has to have somewhere to go that is not the interior.
Design the tapered insulation layout
Where the structural deck cannot be re-pitched, slope gets built above it with tapered insulation — a designed layout of panels that falls toward each drain. This is done as a drawn plan, not improvised on the roof, because a taper layout that is wrong at the edges creates the exact low spots it was meant to eliminate.
Crickets and saddles behind every obstruction
Any curb, wall or wide unit sitting across the flow path dams water behind it. Crickets divert flow around the obstruction. Skipping them is cheap and invisible on the day, and it is where a large share of flat roof leaks begin two years later.
Drain sumps, clamping rings and strainers
The membrane has to be brought down into a sump and clamped properly at each drain, with a strainer fitted. A drain detail done casually leaks directly into the building interior rather than into insulation, which makes it the fastest-appearing failure on this list.
Membrane, edge metal and a flood test where warranted
System installed to manufacturer specification with hot-air welded seams and properly detailed perimeter metal — wind uplift starts at the edge. On critical areas the drainage can be verified with water before the job is called complete. More on installation methods and attachment.
Systems for low slope
What goes on a flat roof, and what it costs
Five systems suit low-slope work. We install all of them, which is the point of our commercial roofing operation in Austin being certified with three manufacturers rather than tied to one.
| System | Suits | Planning range | Service life |
|---|---|---|---|
| TPO membrane | The default for most Austin low-slope buildings. Reflective white surface, heat-welded seams, strong value. | $5.50–9.50 / sq ft | 20–30 yrs |
| EPDM membrane | Forgiving around complex penetrations, long track record, excellent flexibility. | $5.50–9.00 / sq ft | 20–30 yrs |
| PVC membrane | Grease and chemical resistance. The right call where kitchen exhaust discharges onto the roof. | $7.00–12.00 / sq ft | 20–30 yrs |
| Built-up roofing | Multi-ply redundancy where rooftop traffic and equipment service are heavy. | $5.50–9.00 / sq ft | 20–30 yrs |
| Modified bitumen | Durable underfoot, common on smaller commercial and mixed-use low-slope roofs. | $5.00–8.50 / sq ft | 15–25 yrs |
PLANNING RANGES ONLY — and note that TAPERED INSULATION IS A SEPARATE LINE. A bid that corrects slope will read higher
than one that does not, for the same membrane. That difference is the whole reason one roof lasts and the other ponds again.
Actual cost depends on deck condition, tear-off vs recover, insulation thickness and R-value, penetration count and access.
Comparing bids
Four line items that explain a cheaper number
When one flat roof bid comes in noticeably under the others, it is almost never a better price for the same work. It is usually one of these four things missing.
Tapered insulation
The single largest legitimate cost difference between two flat roof bids. Without it, the existing low spots stay exactly where they are.
Crickets and saddles
Small, invisible from the ground, and the reason water dams behind curbs. Easy to leave out of a number and hard to add later.
Cover board
The layer between insulation and membrane that resists hail and foot traffic. Among the most commonly value-engineered-out components.
Deck repair allowance
A bid assuming the deck is sound will change-order when it is not. An allowance makes the number honest up front rather than surprising later.
Texas does not license roofing contractors. There is no state licence to check, so the verification is on you: insurance certificates sent directly by the insurer, workers' compensation, manufacturer certification for the specific system, and references from low-slope commercial buildings rather than houses.
Ask to see a tapered insulation layout from a previous job. A contractor who does this work properly will have one to hand; one who does not will change the subject. The six-point checklist →
Related services
Where to go next
Commercial roof inspection Austin
Free. Slope, drainage and ponding assessed with a written report and photographs.
Commercial roof installation Austin
Attachment methods, seam welding and the detail work a warranty depends on.
White membrane installation
What a reflective surface buys you, aged versus initial reflectance, and where it stops helping.
Commercial roof maintenance in Austin
Drain clearing and the scheduled work that keeps a correctly sloped roof draining.
Commercial roof replacement in Austin
Tear-off versus recover, and how the two approaches compare on a low-slope roof.
ATX Commercial Roofing →
Serving Austin since 2008 — certifications, coverage, warranties and service areas.
Common questions
Flat roof installation — straight answers
How much slope should a flat roof have?
A quarter inch of fall per foot of run is the standard target for low-slope commercial roofing, pitched toward drains or scuppers. Some older buildings were built dead flat and some have settled out of pitch. Where the structural deck cannot be re-pitched, tapered insulation builds the fall into the assembly above it, which is the normal solution rather than an exotic one.
Is standing water on my flat roof a problem?
If it is still there forty-eight hours after the rain stopped, in weather that should have dried it, yes. That is the working industry definition of ponding, and it matters because of weight on the deck, accelerated membrane aging in exactly the spot the seams sit, and the fact that many manufacturer warranties exclude ponding damage. A brief puddle that clears is normal.
Can you fix ponding without replacing the whole roof?
Sometimes. Adding a drain, correcting a blocked one, or building up a localised area can resolve a single low spot on an otherwise sound roof. Widespread ponding across a roof usually means the slope was never right, and that is corrected properly during a replacement with a tapered layout. The inspection tells you which situation you have.
Why is one flat roof bid so much cheaper?
Usually because something is not in it. The four common omissions are tapered insulation, crickets behind curbs, a cover board, and a deck repair allowance. Compare the scopes line by line before the totals — a bid that corrects slope will read higher than one that just re-covers the existing low spots, and that difference is the entire point.
How long does a flat roof installation take?
It depends on square footage, tear-off versus recover, and how much taper work is involved. A straightforward recover on a modest building can be a matter of days; a full tear-off with a tapered insulation layout on a large roof runs considerably longer. The schedule is confirmed in writing before mobilisation, and on an occupied building each day ends with the roof dried in.
Do you install flat roofs on new construction?
Yes, and it is the ideal time to get slope right, because drainage can be designed into the deck rather than corrected above it later. See roof construction for ground-up work coordinated with a GC schedule.
Free flat roof slope & drainage inspection
We map where water is actually going on your roof, check drain capacity against the area it serves, and send a written report with photographs and a planning range. No charge, no obligation.
Request inspectionPRICING & TECHNICAL DISCLOSURE — per-square-foot figures are PLANNING RANGES for budgeting, not quotations; tapered insulation, cover board and deck repair are separate line items not included in those ranges. Actual cost depends on deck condition, tear-off versus recover, insulation thickness and R-value, taper complexity, penetration count, access and current material pricing. A firm price requires a physical inspection. The slope diagram is a SCHEMATIC and is not to scale. Slope targets, ponding definitions and drainage requirements described here are general industry practice; applicable building code, manufacturer specification and the requirements of your specific warranty govern any actual installation. Service-life spans are typical expectations under normal maintenance. The State of Texas does not issue roofing contractor licences; verify insurance, manufacturer certification and references directly.
Commercial Flat Roof Repair Austin: Fix the Drainage, Not Just the Leak
Most commercial flat roof repair in Austin starts with a leak and ends with a patch. The patch holds until the next storm, because the water that found the weak spot is still sitting in the same place. A flat roof repair that lasts changes where the water goes. That's the work we focus on, and it's the same thinking we use as a flat roof installation contractor in Austin, applied to a roof that's already on the building.
| The problem | What you see | The geometry repair |
|---|---|---|
| Ponding in the field | Standing water 48 hours after rain, dirt rings, algae, a low spot that grows each year | A tapered insulation saddle built into the low area so water runs to the nearest drain |
| Water trapped behind curbs | Ponding on the uphill side of rooftop units, hatches and skylights | A cricket on the upslope side that splits the water around the curb |
| Drains sitting high | A ring of standing water around the drain, with the drain itself above the low point | Resetting the drain lower or building a sump, so the roof's lowest point is the drain |
| Not enough drains | Water that has nowhere to go on a large section, often after an addition or a re-roof | Adding a drain or relocating one to where the roof actually falls |
| Parapet walls holding water | Water lines on the inside of parapets after storms | Adding or enlarging scuppers, plus overflow scuppers above the primary drains |
| Clogged outlets | Overflow at one edge while the rest of the roof drains | Clearing drains and scuppers, fitting strainers, and matching downspouts to the outlet |
Where the leak is a puncture, a split seam or failed flashing on an otherwise well-draining roof, that is a membrane repair rather than a drainage problem. Those repairs are covered by system on our Commercial roof repair Austin page. Edge drainage that runs into gutters and downspouts is covered on our Commercial gutters Austin page.
Flat Roof Repair Austin: Patch, Re-Slope or Replace?
Every flat roof repair in Austin lands in one of three places, and the right one depends on how much of the roof holds water and what's underneath. Most of the commercial flat roof repair Austin buildings need sits in the middle column.
Isolated leak, good drainage
The roof drains well and the leak is one failure point. Repair the membrane or flashing and keep the roof on maintenance.
Localized ponding
One or a few areas hold water but the insulation is dry and the roof has life left. Saddles, crickets or a reset drain fix the cause, and the membrane over them is replaced in that area only.
Widespread ponding or wet insulation
Water sits across much of the roof, or core cuts show wet insulation in many areas. A new roof with full tapered insulation is the lasting fix. See Commercial roof replacement in Austin.
What a Flat Roof Installation Contractor in Austin Checks First
A good flat roof installation contractor in Austin approaches a repair the same way as a new roof: by finding out where the water wants to go before deciding what to fix. These are the checks that come before a repair price.
Water marks and dirt rings
Where water has stood shows up as staining, debris rings and algae, even on a dry day. Photos after rain are even better.
Drain elevations
Whether each drain is actually the low point of its area, or sits higher than the roof around it.
Slope check
Measuring fall across the roof to find dead-flat areas and reverse slopes, especially near additions and old repairs.
Core cuts
Small samples through the roof to check whether insulation is dry, damp or saturated. Wet insulation changes a repair into a bigger job.
Deck condition
Sagging between supports can create the low spot in the first place. If the deck is deflecting, re-sloping on top won't hold.
All of this is part of a Commercial roof inspection Austin visit, and it goes into the written scope.
Why Flat Roof Installation in Austin Has to Plan for Downpours
Any flat roof installation Austin buildings get has to deal with rain that comes in short, heavy bursts. A roof can drain a light shower perfectly and still flood its low spots in a 20-minute storm. That's why the same problems keep showing up on repair calls here:
Hail on ponded areas. Membrane that sits under water ages faster, and hail fractures it more easily. After a hail storm, the leaks often show up first where the roof ponds. See Hail damage roof repair Austin.
Freezes. Rare hard freezes turn standing water into ice that pushes on seams and flashing, and the leaks appear in the thaw.
Additions and rooftop equipment. New HVAC units, curbs and building additions often block the original drainage paths. Crickets behind new curbs are one of the most common repairs we do.
For the details that keep water out where the roof meets walls, curbs and penetrations, see our page on Austin commercial roof waterproofing.
Flat Roof Repair Questions
Can a ponding flat roof be fixed without replacing it?
Often, yes. If the ponding is limited to a few areas and the insulation is dry, tapered saddles, crickets or a lowered drain can fix it, with new membrane only over the repaired area.
How much water on a flat roof is normal?
Some water right after rain is normal. Water still standing 48 hours later is the industry definition of ponding, and it should be fixed.
Why does my flat roof keep leaking in the same place after repairs?
Usually because water keeps sitting there. A patch fixes the hole but not the reason water collects. Until the drainage changes, the same spot keeps failing.
Is commercial flat roof repair in Austin covered by insurance?
Damage from a covered event, like hail, often is. Ponding from poor slope or drainage is usually treated as wear or a design issue, and many warranties exclude it. Your policy and carrier decide.
Flat roof holding water?
Send us photos after rain, or tell us where it leaks. We'll find where the water goes and give you a written repair or re-slope scope. Austin flat and commercial roofing since 2008.