Flat & Low-Slope Roofing
Membrane, welded and detailed properly. Not a coating over a bad roof.
1,200+ reviews · 4.8★ on Google Licensed & insured · CSLB #1030917
Serving Fresno, Clovis, Visalia, Sacramento and Bakersfield.
Free for homeowners. $299 for real estate transaction inspections.
- $5.75–12Per sq ft,
membrane systems - WeldedSeams, not
glued or taped - Homes tooCommercial-grade
on residential - FreeInspection with
video proof
- Units, curbs and drains handled as part of the job
- We’ll tell you when a coating is the wrong answer
Flat roof leaking?
Two minutes, three questions. House or commercial building — we’ll come look.
Free · No obligation · We route you to the nearest crew
Why flat is different
On a pitched roof, water leaves. On a flat roof, it waits.
A sloped roof sheds. Water hits it and it is gone in seconds, so a small defect gets a few seconds of exposure per storm.
A flat roof holds. Water sits on the surface until it drains or evaporates, which means every seam, every penetration and every edge detail is under standing water for hours at a time. A defect that would never matter on a pitched roof becomes a leak here.
Which is why the surface material matters far less than people assume, and the seams, the curbs, the drains and the edge metal matter far more. Anybody can roll out a membrane. The job is what happens where that membrane stops.
What we install
Single-ply membrane, heat welded
Single-ply membrane over the appropriate insulation, with the seams heat welded rather than glued or taped. A welded seam fuses the sheets into one piece of material. Adhesive gets old, gives up and lets go — and it does it at exactly the point water sits longest.
Edges and terminations are done in clad metal. The perimeter is where wind gets underneath a flat roof and where most failures start, so it is not a place to improvise.
Yes, on houses too
Plenty of homes around here have a flat or low-slope section — a patio cover, an addition, a porch roof, a section tied into the main pitched roof. Those get treated as an afterthought by most residential roofers, which is why so many of them leak at the transition.
We put commercial-grade membrane on residential low-slope, and we do it because it is more durable, not because it sounds impressive. The same product handling a shopping center holds up fine over your back patio.
Where we say no
We won’t coat a roof that’s too far gone
Coatings get sold hard on flat roofs, because they are quick, cheap on the day and look like a finished job the moment they dry.
Here is our position, and we would rather lose the sale than dress it up.
If a roof is old enough or damaged enough that a membrane is the right answer, a coating over the top of it does not deliver value. You spend money, the underlying roof keeps failing, and in a few years you pay for the removal of both. The coating did not fix the problem — it hid it, and it charged you for the privilege.
Same with foam. It goes on fast, it looks impressive, and when it fails there is nothing to repair, only something to remove.
So we will tell you plainly which one you are looking at. If the roof genuinely supports a coating and it makes sense for your building, that is a real conversation. If it does not, we will say so and quote the job that actually solves it.
The details
Everything sitting on the roof is part of the roof
Rooftop units. Curbs. Ductwork. Drains, scuppers, vents, conduit. On a flat roof there is usually a lot of it, and every single item is a hole through the waterproofing that somebody has to detail correctly.
They also have to move before a new roof can go underneath them. Units come off, ductwork comes out, the roof goes on, new curbs go in where the old ones were too low, and everything goes back. We handle that ourselves rather than working around it or leaving the customer to coordinate three trades.
Drainage gets the same attention. A flat roof that ponds was either built without enough fall or has drains that stopped working, and putting a new membrane over standing water just buys you a newer roof with the same problem.
That work belongs in the bid. When it is left out, the number you were quoted was never the number.
Straight numbers
What a membrane roof costs
Per square foot, installed. The range is wide for a reason, and the reason is insulation.
| System | Per sq ft |
|---|---|
| TPO / single-ply membrane | $5.75–$12 |
Where a job lands in that range depends mainly on insulation requirements and Title 24 compliance, which vary by building and by scope. That is why we estimate flat roofs per job rather than publishing one number and adjusting it later. Deck condition, the amount of rooftop equipment, drainage corrections and access all move it too. Every price is written and flat-rate before work begins.
Verified reviews
What customers say
More than a thousand Google reviews across four California markets, averaging 4.8 stars. Read them →
“After having repeat issues with the previous roofing contractor, we reached out to Grandmark based on online reviews and we were not disappointed. The diagnosis and solution were better.”
“Angel and Antonio are efficient with a great work ethic. Antonio the project manager is communicative and you are given frequent updates until completion of job.”
“Carlos came out and gave us a detailed on site estimate with clear pricing and explanations… I’m so grateful to have a company that didn’t take the check then not communicate or show up for days.”
Related
Depending on the building
Straight answers
Frequently asked questions
Somebody quoted me a coating. Should I take it?
It depends entirely on the condition of what is under it. On a roof with life left, a coating can be a reasonable maintenance decision. On an old or failing roof it is a band-aid that costs more over time, because you eventually pay to remove both the coating and the roof beneath it. We will tell you honestly which situation yours is.
What about spray foam?
Same reasoning. It goes on quickly and looks impressive, but when it fails there is nothing to repair — only something to remove, and removal is not cheap. We would rather install a system that can be maintained and repaired.
My patio roof leaks where it meets the house. Is that this?
Almost certainly. Low-slope sections tied into a pitched roof are one of the most common leak points on a house, and they are usually done badly because the roofer treated it as an add-on. That transition needs a proper membrane and a proper detail where the two systems meet.
Why is the price range so wide?
Insulation. Requirements vary by building and by scope, and Title 24 compliance affects what has to go under the membrane. That single factor moves the number more than anything else, which is why we quote per job rather than per square foot from a website.
Do the air conditioning units have to come off?
Usually, yes, for a full replacement. We handle removal and reset ourselves, including new curbs where the existing ones sit too low, so you are not coordinating between a roofer and another trade.
Do you do repairs on flat roofs, or only replacements?
Both. If a membrane roof has life left and is failing at a specific detail, repairing that detail is the right answer and we will quote it. Replacement is for when there is nothing sound left to repair against.
Find out whether your flat roof needs a repair, a membrane, or neither.
Free inspection, video proof, and a written flat-rate price for the work that actually solves it.