What happens during a roof replacement, step by step

Updated · KeystoneProGuide editorial team

What happens before work starts?

Paperwork, and Pennsylvania law sets much of it. In Pennsylvania a roofing contract over $500 must be in writing and signed by both of you, with a description of the work, approximate start and completion dates, the total price and notice of your right to cancel. The Attorney General says the contractor must give you a free copy and may not take any payment until the contract holds every required item and you have signed it.

The Insurance Institute for Business and Home Safety (IBHS) suggests the contract also cover cleanup and what happens if weather delays the job, and it says the contractor should obtain all required permits. The National Roofing Contractors Association (NRCA), the trade's association, adds one clause people forget: who is responsible if rain gets in while the roof is open and damages ceilings or walls. It says to make sure the contract addresses that before you sign.

Ask who will supervise and how many workers will be on site; NRCA suggests getting the supervisor's name. The contract's dates are approximate, and none of the authority sources read gives a standard length for a roof job, so ask the roofer for its own estimate in writing.

What happens to the old roof?

Usually it comes off. Under the 2021 International Residential Code, which Pennsylvania's building code adopts, a roof replacement means removing the existing layers down to the roof deck. A new covering may go over the old one only in limited cases, and never where the existing roof is water soaked or too deteriorated to be a base, is slate or tile, or already has two or more layers.

Tear-off is priced separately in many quotes. Fixr puts removal and disposal at about $50 a square, a square being 100 square feet of roof, and up to $150 a square for heavy materials or several layers.

If the house is old, the material coming off matters. The Environmental Protection Agency lists roofing shingles among products that may contain asbestos, and says that removing such material must be done only by trained and accredited professionals. Ask before the job whether the roofer has checked.

What happens once the deck is exposed?

This is where a quote can change. If boards in the deck have to be replaced, Fixr gives $2 to $8 a square foot for new decking. A good contract says how such extra work is priced and approved. If the job is on time and materials, the Attorney General says the cost may not go more than 10% over the written estimate unless you sign a change order.

The code also says the roof structure must be able to carry the new covering and the loads of the materials and equipment during installation. NRCA makes the same point about tile, which it says is heavy enough that you need to verify the house can support it before switching to it from a lighter material.

What goes on before the shingles?

Several layers you will not see afterwards:

  • Flashing. The code says existing flashings, edgings and vents that are rusted, damaged or deteriorated must be replaced, and that flashing is rebuilt to the manufacturer's instructions.
  • Ice barrier. Where the local code records a history of ice backing up at the eaves, the code requires an ice barrier from the roof edge to at least 24 inches inside the wall line.
  • Underlayment. NRCA recommends one layer of No. 15 asphalt-saturated underlayment on asphalt shingle roofs sloped 18 degrees or more, and two layers on slopes of 14 to 18 degrees. It says it does not recommend asphalt shingles at all below 18 degrees, though some manufacturers and model codes allow them.
  • Ventilation. NRCA suggests balancing attic ventilation between the eaves and the ridge, with about 50% of the vent area at or near the ridge, and notes that shingle warranties may require minimum ventilation.

If rain falls on the underlayment before the shingles go on and it wrinkles, NRCA says it can usually stay if the wrinkling is not bad enough to affect the shingles.

How are the shingles put on?

To the maker's instructions and the code. NRCA recommends galvanized steel or equivalent corrosion-resistant roofing nails for asphalt shingles and says to check the governing code and the manufacturer's requirements. The code requires asphalt shingles to be fastened to a solidly sheathed deck. In cold weather, NRCA says self-sealing strips may not bond until it warms up, and recommends hand-sealing shingles in windy areas.

Is the work inspected?

Where a permit was issued, yes. In Philadelphia, for example, the permit lists the inspections to be arranged, and L&I issues a Certificate of Approval once they are all passed. Elsewhere, ask your municipality what it inspects.

What should you check before the final payment?

  1. Walk the property for nails and debris, and look at the gutters and landscaping.
  2. Look at the ceilings and the attic for new stains after the first heavy rain.
  3. Get the manufacturer's warranty certificate; NRCA says to make sure the contractor provides one.
  4. Get the workmanship warranty in writing, and keep both with the receipt, as the Federal Trade Commission advises for any warranty and receipt.
  5. Get the permit's final approval where one was required.

Do not sign anything saying the work is complete, or pay the balance, until it is. The Pennsylvania Insurance Department gives that advice for storm repairs, and the FTC says never to make the final payment until the work is done and you are satisfied.

Questions to ask a roofer before you hire turns these stages into a checklist, and what Pennsylvania requires of roofers covers the contract rules in full. Roofers in the area are listed on the roofers directory page.

Sources

  1. AG Sunday Warns of Potential Scams Following Deadly Storms that Impacted Pittsburgh and Surrounding Areas, Pennsylvania Office of Attorney General
  2. Tips for Hiring a Roofing Contractor, Insurance Institute for Business & Home Safety (IBHS)
  3. Chapter 9 Roof Assemblies, 2021 International Residential Code, International Code Council
  4. How Much Does a Roof Replacement Cost? [2026 Data], Fixr
  5. Resources (frequently asked questions), National Roofing Contractors Association (NRCA)
  6. Get permits without plans (EZ permits), City of Philadelphia
  7. How To Avoid a Home Improvement Scam, Federal Trade Commission
  8. Shapiro Administration Provides Advice on Claims, Avoiding Scams Following Strong Storms and Flooding, Pennsylvania Insurance Department
  9. Selecting a Contractor, National Roofing Contractors Association (NRCA)
  10. Warranties, Federal Trade Commission
  11. Protect Your Family from Exposures to Asbestos, U.S. Environmental Protection Agency
  12. 34 Pa. Code § 403.21. Uniform Construction Code., Commonwealth of Pennsylvania (Pennsylvania Code)
  13. Frequently Asked Questions: Home Improvement Contractor Registration, Pennsylvania Office of Attorney General
  14. Roofing Materials, National Roofing Contractors Association (NRCA)

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