Request a free quote using the quote button on this page.
What this job is
Flat roof replacement is a full re-roof for a low slope roof. The old system is removed or prepared as the scope requires. A new waterproof membrane system is installed as a complete system.
A flat roof is not truly flat. It has a low slope that should move water to drains, scuppers, or gutters. When that slope or drainage fails, water sits. That is a core issue this job must solve.
This page covers replacement only. It is for roofs where the membrane, seams, insulation, or deck have reached the end of their useful life. Related pages include roof tear off and re-deck and gutter replacement with a new roof.
Signs you need flat roof replacement
Look for patterns, not just one spot.
- Leaks in several places, or leaks that return after prior work.
- Seams that are open, cracked, or lifting.
- Membrane that is blistered, split, or worn thin.
- Pools of water that stay long after rain has stopped.
- Soft spots when the roof is walked on, which can point to wet insulation or deck damage.
- Stains, mold smell, or wet ceiling tiles below the roof.
- Edges and flashing that have pulled away from walls or curbs.
A single seam flaw is a small issue. Wide seam failure, wet insulation across large areas, and chronic ponding point to system failure. At that stage, a full replacement gives you new seams, new flashing, and a chance to fix drainage in one job.
Process step by step
- First review. The provider checks the roof surface, seams, drains, edges, and access points. They may check below the deck for signs of water.
- Core and layer check. They confirm how many old layers exist and if insulation is wet. This decides if tear off is needed.
- Scope and quote. The written scope should list tear off, deck work, insulation, membrane type, seam method, flashing, drains, and clean up.
- Tear off. Old membrane and wet or damaged insulation are removed as scoped. Debris is taken down in a planned way.
- Deck check. The deck is checked for rot, rust, or weak sections. Bad areas are replaced as agreed.
- Insulation and slope. New insulation is set. Tapered pieces may be used to guide water to drains and cut ponding.
- Membrane install. Rolls or sheets are laid out, secured, and joined at seams by the method for that material.
- Flashing and edges. Walls, curbs, vents, drains, and roof edges are flashed and sealed as a system.
- Drainage check. Drains and scuppers are tested. The crew checks that water flows where it should.
- Final walk. Seams, edges, and details are inspected. You walk the job with the provider and review the scope.
Materials and options
Four common options are used for low slope replacement. Your provider should explain them in plain terms.
TPO. A light colored single ply membrane. Seams are heat welded. It reflects sun well and is widely used on homes and commercial buildings with low slope roofs.
PVC. Also a single ply membrane with heat welded seams. It holds up well to standing water risk and to some chemicals that can harm other membranes. Seams are a key strength when done well.
EPDM. A rubber single ply membrane, often black. Sheets are large, so there can be fewer seams. Seams are taped or glued, so seam care and edge details matter a lot.
Modified bitumen. An asphalt based system, often installed in layers. It can be torch applied, cold applied, or self adhered based on the product. Multiple plies can add toughness under foot traffic.
No membrane works if seams, flashing, or drainage are poor. Ask how seams will be made, how edges will be finished, and how ponding will be reduced. Also ask about insulation type and thickness, and whether a cover board will be used to protect the membrane.
Cost factors
We do not list price ranges on this page. Cost is set by the facts of your roof. Key factors include:
- Roof size, height, and access for crews and materials.
- Number of old layers and amount of tear off and disposal.
- Amount of wet insulation or deck work found.
- Membrane type, thickness, and seam method.
- Insulation type, thickness, and use of tapered pieces for drainage.
- Number of drains, curbs, vents, walls, and other details.
- Edge metal, flashing, and gutter or scupper work in the scope.
Ask for a written quote that lists these items. Compare quotes only when the membrane, insulation, and drainage work match.
How to choose a provider
- Ask which membrane systems they install most often, and why they propose one for your roof.
- Ask how they will handle ponding, drains, and slope.
- Ask how seams will be made and checked.
- Ask what happens if wet insulation or deck damage is found, and how changes will be approved and priced.
- Ask for proof of licensing and insurance that the provider is required to show in your area, and check it yourself.
- Ask for a schedule that notes weather limits for install.
How the referral works
Request a free quote using the quote button on this page. Share your city and roof details, and get connected to a local provider who offers flat roof replacement. You then deal direct with that provider for quotes, contracts, and work.
FAQ
What counts as a flat roof?
A flat roof is a low slope roof. It looks flat, but it should have a slight slope so water can drain. If water sits in pools for a long time after rain, drainage needs work. A full replacement is a chance to fix slope, drains, and edges as part of one system.
Which flat roof membrane should I choose?
There is no single best choice for every building. TPO, PVC, EPDM, and modified bitumen each suit different roofs, budgets, and weather. What matters is correct seams, good drainage, and a crew that installs that system often. Ask your provider why they recommend one system for your roof and what the seams and edges will be.
Why does ponding water matter so much?
Standing water adds weight and works on seams and edges day after day. It can shorten the life of the roof and raise leak risk. A replacement should address why water ponds, not just cover it. That may mean tapered insulation, new drains, or changes to scuppers and edge details.
How long does flat roof replacement take?
Timing depends on roof size, access, number of layers to remove, and weather. A small simple roof may take a few days. A large or complex roof can take longer. Your provider should give a schedule that covers tear off, deck checks, insulation, membrane work, and final checks for seams and drainage.
Can a new flat roof go over the old one?
In some cases a cover board and new membrane go over an old roof, but it is not always wise. If the old roof is wet, damaged, or has too many layers, full tear off is the sound path. A provider should check the old system and explain the choice in writing before work starts.
Areas we connect
We connect homeowners in these areas with local providers:
You can also review tile roof replacement for pitched tile roofs.
Common questions
What counts as a flat roof?
A flat roof is a low slope roof. It looks flat, but it should have a slight slope so water can drain. If water sits in pools for a long time after rain, drainage needs work. A full replacement is a chance to fix slope, drains, and edges as part of one system.
Which flat roof membrane should I choose?
There is no single best choice for every building. TPO, PVC, EPDM, and modified bitumen each suit different roofs, budgets, and weather. What matters is correct seams, good drainage, and a crew that installs that system often. Ask your provider why they recommend one system for your roof and what the seams and edges will be.
Why does ponding water matter so much?
Standing water adds weight and works on seams and edges day after day. It can shorten the life of the roof and raise leak risk. A replacement should address why water ponds, not just cover it. That may mean tapered insulation, new drains, or changes to scuppers and edge details.
How long does flat roof replacement take?
Timing depends on roof size, access, number of layers to remove, and weather. A small simple roof may take a few days. A large or complex roof can take longer. Your provider should give a schedule that covers tear off, deck checks, insulation, membrane work, and final checks for seams and drainage.
Can a new flat roof go over the old one?
In some cases a cover board and new membrane go over an old roof, but it is not always wise. If the old roof is wet, damaged, or has too many layers, full tear off is the sound path. A provider should check the old system and explain the choice in writing before work starts.