Roof replacement
A roof replacement is mostly the parts you will never see
The shingle is the part you choose and the part you look at. It is not the part that decides whether the roof leaks in year seven.
What actually gets installed
A replacement is an assembly, and it is built from the deck up. The roof anatomy drawing shows the whole stack in section, but the short version is six layers that each do one job.
- Decking
- Inspected once the old roof is off. Anything soft, delaminated or rotten is replaced by the sheet, because a nail in soft OSB is not holding anything.
- Ice and water shield
- Self-adhering membrane at the eaves, in the valleys and around penetrations. In a freeze-thaw climate this is the layer that stops an ice dam from pushing water backwards under the shingles.
- Synthetic underlayment
- Across the rest of the deck. It is the secondary barrier for the day a shingle goes missing, and it does not wrinkle when it gets wet the way felt does.
- Drip edge and starter
- Metal at the eaves and rakes, and a purpose-made starter course with the adhesive strip in the right place. This is the edge detail that decides how a roof behaves in a wind event.
- Field shingles
- Nailed in the manufacturer-specified pattern, in the nail line, at the specified count per shingle. Six nails where six are specified.
- Ventilation
- Ridge exhaust matched to soffit intake. A ridge vent with blocked intake pulls conditioned air out of the house instead of air out of the eaves.
What happens on the day
Protection first
Landscaping, air conditioning units, windows and driveways covered before anything comes off. Tear-off is a messy process and the mess is predictable.
Tear off to the deck
Every layer removed. If there are two or three old layers up there, that is found now rather than guessed at earlier.
Inspect and repair the deck
Walked, sounded and looked at from the attic side where access allows. Bad sheets come out. You get told about it while it is still visible, not afterwards.
Dry it in
Ice and water shield at the eaves and valleys, underlayment over the rest. At this point the house is weather-tight even if the day ends early.
Edge metal, then shingles
Drip edge, starter, then field courses running up to the ridge. Flashings at every wall, chimney and penetration — new metal, not the old metal reused.
Ventilation and clean-up
Ridge vent cut and installed, magnetic sweep over the whole property, and a walk-round with you before anyone leaves.
The decisions that actually matter
| Decision | What it changes | What to ask |
|---|---|---|
| Tear-off or overlay | An overlay hides the deck and traps heat against the new shingles. It also makes the next replacement harder. | Ask what the current layer count is, and whether the deck has ever been seen. |
| Ice and water coverage | How the roof behaves in a freeze-thaw winter, and whether an ice dam finds a way in. | Ask how far up from the eave it runs, and whether valleys and penetrations get it too. |
| Flashing: new or reused | Reused step flashing is the most common hidden shortcut on a replacement. | Ask directly whether the chimney and wall flashings are being replaced. |
| Ventilation | Whether the new roof runs at attic temperature or bakes from underneath. | Ask what the intake is, not just what the exhaust is. |
| Nailing | Uplift resistance at the edges, where wind damage starts. | Ask for the nail count per shingle and whether it is hand-nailed or gun-nailed to a set depth. |
A written scope that names the underlayment, the ice and water coverage, the flashing plan and the nail count is a scope you can compare. A scope that says "install new roof" is not.
How long it takes
Most single-family replacements in this market are a one-day or two-day job once the crew is on site, weather permitting. Steep roofs, cut-up roofs with a lot of valleys and dormers, and any roof where the deck turns out to be in poor condition take longer. Slate and tile are a different trade and a different timeline.
Want the deck condition and layer count established before you make a decision?
Request a free inspectionDo I need to be home?
Not for the whole job, but it helps to be there at the start and at the walk-round at the end. If the deck needs repair you will get a call and photographs while the deck is still open.
What happens to my gutters?
Gutters usually stay. Where drip edge has to go in behind the back of the gutter, the gutter is loosened and reset rather than replaced. If a gutter is already pulling away from a rotten fascia, that is a carpentry repair and it gets called out separately.
Can you replace just one slope?
Sometimes, on a roof with genuinely independent planes and a clear reason. It is worth knowing that a partial replacement will not match the weathered shingles next to it, and that the older section still ages on its own schedule.
Is a second layer ever acceptable?
It is legal in many jurisdictions within limits, and it is almost never the better decision. It hides the deck, it shortens the life of the new shingles by holding heat, and it doubles the tear-off on the next roof.
All work is performed by licensed and insured local roofing professionals.