Roof Replace - Before, During, or After Solar Decision Tree
Why this matters
A 25-year solar array on a 12-year-asphalt roof is a planning failure that gets paid back in 15 years when the panels come off, the roof gets replaced, and the panels go back on. The worst-case sequence is a full PV system, then a full reroof, then a detach-and-reset that adds roughly a third again on top of the reroof and buys the customer nothing. The order of roof and solar matters at the time of sale. This tree splits the call into "replace roof first," "do them together," "let the roof finish out and replace later," or "do nothing - this roof has runway." Wrong calls are expensive; defensible calls keep the customer trusting the contractor.
The decision flow at a glance:
Reroof before or after solar?
|
+-- 1. Adjusted roof life < 10 yr? --> REROOF FIRST
|
+-- 2. Adjusted life 20+ yr? --------> SOLAR FIRST
|
+-- 3. Adjusted 10-20 yr? -----------> CASE BY CASE
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+-- 4. 3-tab 10+ years old? ---------> REROOF. PERIOD.
|
+-- 5. 3-tab under 10 yr? -----------> SOLAR +
| DOCUMENT
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+-- 6. Architectural 10-15 yr? ------> CUSTOMER
| DECISION
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+-- 7. Tile, underlayment 20+? ------> REROOF
| UNDERLAYMENT
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+-- 8. Standing seam under 30 yr? ---> SOLAR (S-5
| CLAMPS)
|
+-- 9. Adjusted = life - 5yr? -------> USE THAT NUMBER
Symptom presentation
Three customer asks drive the diagnosis:
- New solar quote on a home with an existing roof.
- Existing solar that needs work and the roof underneath is aging.
- Solar plus reroof bundled by an integrated company.
The data needed in each case is roof type, age, condition, climate, and solar system life expectancy.
Quick checks - 20 minute pass
- Roof type and age. Asphalt 3-tab, asphalt architectural, tile (clay or concrete), metal standing seam, metal exposed-fastener, EPDM, TPO, slate, cedar shake.
- Roof age and condition. Walk it, document granule loss, missing tabs, soft spots, sealant failures at penetrations.
- Roof manufacturer warranty period and effective remaining years.
- Solar system expected life: panel warranty 25-30 years, inverter 10-15 years (string) or 20-25 (microinverter).
- Climate exposure - UV, hail, freeze-thaw, wildfire ember zone, salt aerosol.
Isolation tree
Step 1 - Roof type expected life
Asphalt 3-tab: 15-20 years total in moderate climate, 12-15 in hot or hail-prone. Confirm install date.
Asphalt architectural: 25-30 years in moderate climate, 20-25 in hot or hail-prone.
Concrete tile: 50-plus years, but underlayment fails at 25-30; the underlayment is the actual watertight membrane.
Clay tile: 75-100 years for tile; underlayment 25-30.
Standing seam metal: 40-50 years.
Exposed-fastener metal: 25-40, fastener seals fail at 15-20.
EPDM / TPO flat roof: 20-30 years.
Slate: 75-150 years.
Step 2 - Age vs solar life simple math
Work with ADJUSTED remaining life, meaning remaining roof life minus a 5 year buffer, because a roof that fails the year the buffer runs out still means panels come off. Use the adjusted number in every branch below:
- Adjusted remaining life under 10 years, against a solar expected life of 25-plus: reroof before solar.
- Adjusted remaining life 10 to 20 years: case-by-case, see below.
- Adjusted remaining life over 20 years: solar first or together; no reroof needed.
Step 3 - Specific routes by roof type
Asphalt 3-tab, 10-plus years old: reroof first. Period.
Asphalt 3-tab, less than 10 years old in moderate climate: solar over the existing roof; document expected detach-reset at year 15.
Asphalt architectural, less than 10 years old: solar.
Asphalt architectural, 10-15 years old: customer decision. If they intend to stay 20-plus years, reroof first. If they intend to sell within 5-7 years, solar over existing.
Tile roof (concrete or clay), tiles intact, underlayment age unknown: solar with caution. Reroof labor is a major project (panels off, tiles off, underlayment replace, tiles back, panels back). If underlayment is 20-plus years old, reroof or at least replace underlayment before solar.
Standing seam metal, less than 30 years old: solar with appropriate clamps (S-5! brackets or similar). No reroof needed for at least 15 years.
Exposed-fastener metal, age unknown: pull and inspect fasteners. If fastener seals are at end of life (cracked or chalking), reroof before solar; otherwise solar over.
EPDM/TPO flat, less than 10 years old: solar with ballast or proper penetration patching. Document membrane warranty for solar attachment.
Slate: most slate roofs are old enough to suspect the underlayment but the slate itself is fine for solar life. Hook installations (penetrate through slate) are specialty work; consult slate roofer.
Cedar shake: do not solar over cedar shake. Replace with asphalt or metal first.
Step 4 - Climate factors that shift the call
Hot desert (Phoenix, Las Vegas): UV degrades asphalt 30 percent faster than rated life. Subtract 5 years from manufacturer rating.
Hail country (Texas, Oklahoma, Colorado Front Range): hail damage is the most common roof-life shortening event. An older asphalt roof has not had hail tested; replace before solar.
Wildfire ember zone (CWPP-designated California, Oregon, Washington areas): Class A fire-rated roof underlayment is required for solar permitting in some AHJs. Confirm before quoting.
Salt aerosol coastal: corrodes metal, accelerates asphalt granule loss. Subtract 3-5 years.
Freeze-thaw heavy (Upper Midwest, Northeast): ice dam damage to asphalt is the main shortening event. Inspect carefully.
Step 5 - Customer scenario adjustments
Customer plans to sell within 3 years: solar over existing roof is acceptable; next owner inherits the planning issue. Disclose.
Customer plans to stay 10-20 years: reroof if existing has less than 10 years remaining.
Customer plans to stay 20-plus years: reroof anything below 15 years remaining.
Customer has solar quote in hand but installer did not address roof: red flag. Pause solar contract, get roof inspection.
Step 6 - Cost-of-bundling consideration
Reroofing while panels are off requires panel removal labor (a separate scope, roughly a crew-day plus electrical disconnect on an average residential system) and reinstall labor (similar again). Together the detach-and-reset commonly lands near a quarter of the reroof itself, pure waste against the alternative sequence. Doing the reroof BEFORE solar avoids this labor entirely. Doing it AFTER solar incurs the full detach-and-reset.
Reroofing simultaneously with solar (panels never go up over the old roof): the cleanest path, but only available if the customer has roof and solar contractors coordinated, which is rare outside integrated companies.
Confirming the diagnosis
Document roof age, current condition with photos, remaining warranty, and the chosen sequence in writing. The signed acknowledgement is the artifact that closes out a future "you should have told me" complaint when the panels come off at year 15 for the reroof.
Remediation routing
- Asphalt 3-tab, under 10 years: solar over, and document the detach-reset the customer should expect around the roof's year 15.
- Asphalt 3-tab, 10 years or more: reroof first. The short service life makes this the one branch with no case-by-case.
- Asphalt architectural, under 10 years: solar over, plan for detach-reset around year 18-22.
- Asphalt architectural, 10-15 years: case-by-case; reroof first if the customer plans long-term occupancy.
- Asphalt architectural, over 15 years: reroof first.
- Tile, underlayment over 20 years old: reroof underlayment first.
- Metal under 20 years: solar over.
- Flat roof under 10 years: solar over.
- Cedar shake: replace roof type entirely first.
- Slate: specialty consultation.
References
- NRCA Roofing Manual, Steep-Slope Roof Systems.
- SEIA Solar Roof Best Practices Guide.
- UL 2703, Mounting Systems, Mounting Devices, Clamping/Retention Devices, and Ground Lugs for Use with Flat-Plate Photovoltaic Modules.
- ASCE 7 Minimum Design Loads, attachment uplift for solar arrays.
- Manufacturer warranty terms for major asphalt brands (GAF Timberline HDZ, CertainTeed Landmark, Owens Corning Duration).