Replacement & Installation
Flat and low-slope roof replacement in San Jose
Flat roofs fail at the water they cannot shed. A replacement is the chance to fix that for good: new membrane, tapered insulation where the water sits, and clean edges at every drain and wall.
What we treat
- Concrete and clay tile
- Composition shingle
- Flat, torch-down and TPO
- Spray foam
- Standing seam metal
Quick answer. Flat roof replacement in San Jose removes the failed membrane down to a sound deck, adds tapered insulation or crickets where water ponds, and installs a new single-ply TPO or PVC membrane or a torch-down modified bitumen system, with new edge metal, scuppers and flashing, under a permit that documents the cool-roof rating.
Updated September 2026
The job
When a flat roof is past repair
A flat roof with a few blisters is a repair. A roof that ponds after every storm, has patches on its patches, or has wet insulation under large areas is a replacement. Wet insulation is the tell: it adds weight, rots the deck, and keeps leaking even after the membrane is patched.
Replacement is also when drainage gets fixed. Most ponding comes from a deck that sags or a roof that was never sloped to its drains.
Your options
TPO, PVC or torch-down?
All three work; the roof's use decides.
| Question | TPO | PVC | Torch-down |
|---|---|---|---|
| Best for | Homes and offices | Restaurants, chemical exposure | Foot traffic, many penetrations |
| Seams | Hot-air welded | Hot-air welded | Torched laps |
| Reflectivity | High (white) | High (white) | Good with cool cap sheet |
| Relative cost | Moderate | Higher | Moderate |
Jobs this page covers
TPO and PVC single-ply
Single-ply membranes come in wide sheets whose seams are welded with hot air, so the seam becomes as strong as the sheet. White TPO and PVC reflect most of the sun, which keeps the rooms below cooler and meets cool-roof rules without extra work. PVC handles grease and chemicals better, which is why it goes on restaurants; TPO is the usual choice on homes and offices. Both are fastened or fully adhered to suit the deck, and both flash cleanly around the curbs flat roofs always have.
Torch-down modified bitumen
Torch-down builds a two or three ply system from a base sheet and a granulated cap sheet heated into place. It is tough underfoot, which suits roofs with decks, equipment or frequent foot traffic, and it bonds well around the many small penetrations older buildings have. Cap sheets come in cool-rated white granules. Torch work is done with a fire watch and never near dry wood without protection. It is also the easiest system for a future repair, since heat and a new ply are all a patch takes.
Tapered insulation for drainage
Tapered boards are cut so the roof falls toward its drains and scuppers even when the framing is dead flat. Crickets between drains split the flow so water never sits in the middle of a run. Getting the slope right costs a little more in material and saves years of ponding, which is what breaks down membranes and rots decks. Where headroom at a door threshold is tight, we slope around it. The drainage layout is drawn on the scope before installation.
Parapet and scupper details
Most flat roof leaks start at the edges: parapet walls, scuppers, drains and the curbs of HVAC units. On a replacement we carry the membrane up and over the parapet, add coping or counterflashing on top, size scuppers and collector boxes for storm flow, and rebuild every curb flashing. Those details take longer than the field of the roof and are what makes it last. Drains get new clamping rings and strainers so leaves stop at the grate instead of in the pipe.
Cost
What sets the price of a flat roof replacement
Flat roofs are priced by area, system and how much wet material comes off.
- Wet insulation Saturated insulation has to come out and be replaced; a moisture scan tells us how much.
- Membrane system PVC costs more than TPO; torch-down sits in between depending on plies.
- Tapered insulation Correcting drainage adds material and labor, and saves the roof.
- Edges and parapets Coping, scuppers and curb flashing are detailed work.
- Deck repairs Soft sheathing under ponding areas is replaced.
- Access Tight lots and equipment on the roof add setup time.
What we see on San Jose roofs
A lot of the low-slope work we do in Willow Glen traces back to its mid-century tracts, including roughly 350 Eichler homes in Fairglen and the neighboring pockets, built between 1957 and 1962 with flat and barely pitched roofs over post-and-beam framing. On those roofs, and on any permitted flat re-roof in the city, Title 24's cool-roof rules apply once more than half the roof is replaced, so the new membrane has to carry a CRRC rating. White single-ply and cool-rated cap sheets meet that without changing the low profile.
Scope
What the replacement includes
Every flat roof scope we write lists these lines.
- Moisture survey of the existing roof
- Removal of membrane and wet insulation
- Deck repairs where soft
- Tapered insulation or crickets to the drains
- New membrane with welded or torched seams
- Parapet, coping, scupper and curb flashing
- Flood test of drains before sign-off
What happens after you call
How a flat roof replacement runs
- 1
Moisture check
We map wet insulation and soft decking before quoting.
- 2
Drainage plan
Tapered layout and crickets drawn around the drains.
- 3
Permit
Filed with the membrane's cool-roof rating.
- 4
Tear-off
Membrane and wet insulation removed, deck repaired.
- 5
Install
Insulation, membrane, edges, scuppers and curbs.
- 6
Water test
Drains flooded and checked before we leave.
Brands we install and service
FAQ
Questions we get asked
Sometimes, if the old roof is dry and a single layer. A moisture scan decides; wet insulation always comes out.
A well-drained single-ply or torch-down roof commonly runs twenty years or more. Ponding cuts that sharply.
Low-slope roofs are mostly invisible from the street and from neighboring yards.
Yes, with single-ply, torch-down or spray foam depending on the house and the owner's priorities.
Yes, above 25 percent of the roof. We file it and document the cool-roof rating.
Same category
Related roofing work
Roof Replacement
Composition shingle re-roofs with Class A and cool-roof options, permitted and inspected.
Learn moreTile Roof Replacement
Concrete and clay tile re-roofs, including lift-and-relay with new underlayment.
Learn moreMetal Roof Installation
Standing seam and stone-coated steel, including over existing shingles.
Learn moreSpray Foam Roofing
New foam roofs and recoats for Eichler and other low-slope homes.
Learn moreGet the flat roof scanned and priced
We check for wet insulation, plan the drainage, and price the membrane options side by side.