Flat Roof Replacement by System
Modified bitumen
Fixr calls modified bitumen the most affordable flat roofing material. Guides put it at $4 to $7.50 a square foot, about $4,900 to $14,600 installed, with 10 to 20 years of life. The rolls are heat-welded with a torch, or come as self-adhesive sheets. A granulated cap sheet needs no added surfacing under the HVHZ code. On a wood deck, the base sheet is nailed with:
- 12-gage annular ring-shank nails with at least 20 rings per inch
- heads at least 3/8 inch across, through tin caps
- the spacing pattern printed in the system's product approval
Built-up and hot-mopped roofs
Built-up roofing is layers of felt and asphalt topped with gravel, or with a coating on a smooth roof. It costs $3.50 to $7.50 a square foot and lasts 20 to 30 years by guide figures, but takes longer to install than single-ply. The HVHZ code is specific about the top: at least 400 pounds of gravel per 100 square feet on slopes of 3:12 or less, with at least half of it bedded in the flood coat. A smooth-surfaced roof needs an approved aluminized or emulsion coating instead.
Single-ply TPO and PVC
Single-ply sheets go on fastest of the three groups. PVC runs $5 to $12 a square foot with 20 to 30 years of expected life, and EPDM rubber $4 to $10 with 15 to 20. TPO falls between EPDM and PVC on price and durability; its attachment methods and thicknesses are on the TPO roofing page.
Tapered insulation and drainage
Tapered boards build fall into a roof that was framed dead flat. In new construction the HVHZ minimum is 1/4 inch per foot. Before work starts, the code makes the contractor tell the owner if ponding is possible and recommend a structural review when it is. Two more limits apply. Lightweight concrete can't be poured over an existing deck without an engineer's sign-off on the extra weight, and insulation boards need their own product approval within the roof system.
Tear-off or recover
A recover keeps the old roof in place as the base for the new one. In the HVHZ that's allowed once, and only after the old roof passes these tests:
- moisture survey (TAS 126): no more than 5% moisture in the membrane, 8% in board insulation
- bonded recover: uplift test of the old membrane (TAS 124)
- fastened recover: field pull test of the fasteners (TAS 105), and every bit of gravel removed first
- all blisters cut and repaired before the new layer goes on
Tear-off adds $1 to $2 a square foot but answers every one of those questions by removing them.
Why Pompano Beach homeowners call Pompano Beach Roofers
- Calling or sending the form costs you nothing
- Your request goes to one roofer, not a list of bidders
- Ask for tear-off, deck work and the permit on one itemized quote
- Get the roofer's CC or RC license number and check it yourself
What Changes a Flat Roof Replacement Price
Deck type
Lightweight insulating concrete, gypsum and wood-fiber decks need a fastener pull test, and steel decks thinner than 22 gage must be field tested before a new system goes on. A failed test adds an engineer's attachment design.Wet insulation
Anything that fails the moisture survey comes off and gets replaced.Drains and penetrations
Each curb, drain or skylight adds work at the flashing; on TPO jobs, guides add $200 to $500 for them.Permit paperwork
Low-slope roofs have their own sections on the city's HVHZ permit form; roof replacement walks through the permit and inspections.
See flat roof repair if the roof might have a few more years in it.