A roof replacement is more than a new outer layer. On a Philadelphia house it runs from a City permit to a signed certificate, and the steps between are partly set by L&I's EZ re-roofing standard and partly by the estimate you agree to. This list follows the job in order; "standard" marks what the City requires.
1. Permit and, if needed, historic approval
- EZ permit for a roof covering replacement, with the manufacturer's complete installation instructions filed (standard). $69 on a one- or two-family house plus surcharges.
- Historical Commission approval first if the house is designated (standard). See historic districts.
2. Tear-off
- Removal of every existing layer where the roof is deteriorated, slate or tile, or already has two coverings (standard).
- Disposal of debris at the end of each working day (standard).
- Protection of the house and the sidewalk while material comes down.
3. The deck
- Replacement of rotted deck boards or sheets. Planned replacement over 10% of the sheathing is outside the EZ permit, and damage found during tear-off must be reported to the inspector (standard). Ask for a unit price.
- Slope corrections on a flat roof so water reaches the drain: the code minimum is 1/4 inch per foot for membranes (IRC 2021 R905).
4. Insulation
- Optional, but if insulation is altered it must reach R-49 under the 2021 energy code (standard). On a rowhouse with no attic, the Rowhouse Manual notes, rigid insulation can go "between the decking and beneath the roofing material."
5. The covering
- Flat roof: modified bitumen, EPDM, TPO or built-up, per the maker's instructions (standard). See flat roof systems.
- Pitched roof: asphalt shingles only at 2 in 12 or steeper, in a listed wind class, with drip edge at eaves and gables; double underlayment between 2 in 12 and 4 in 12 (standard; IRC R905.2.2).
- Slate: new or sound salvaged slate (standard allows reinstalling sound slate).
- Fire class B or better for most houses (standard).
6. Edges, flashing and drains
- Membrane run up the parapet and over or under the coping.
- Joints with the neighbors' roofs along the party walls.
- Flashing rebuilt to the maker's instructions; metal primed where bitumen is adhered; rusted or damaged vent flashing, edgings, drain outlets, drain collars and counter-flashing replaced, not reused (standard).
- Roof drain, scupper or gutter and the downspout connection. Storm water must end up on your property (Rowhouse Manual).
7. Rooftop items
- Hatch, vent stacks and existing skylights flashed into the new roof. New skylights and moved equipment need a different permit (standard).
- A roof deck has to come off and go back, or be built on its own structure; zoning and building permits apply to a new one (Rowhouse Manual).
8. Inspection and the certificate
- City inspection under the permit.
- Form TP_019_F, the Roof Replacement Certification, filed by the contractor and "presented by the Contractor to the building owner/owner's agent upon completion."
- The manufacturer's warranty and the contractor's own workmanship terms, in writing.
What an estimate leaves out of this list is a question to ask before signing; see what sets the cost and contract and cancellation.