Roof Condition Assessment Before an Array Goes On

Purpose

A module carries a performance warranty measured in decades and the roof under it does not. This procedure answers one question with evidence: will this roof outlive the array, and if not, is the customer deciding that now or in year eight, when the answer costs them a full removal and reinstall on top of the roofing itself.

It answers the crew's question at the same time: what does the array attach to. Rafter size and spacing, sheathing type and thickness, and stick-built versus trussed framing decide the attachment layout, and getting that wrong produces the two worst outcomes in residential solar - a lag that missed the rafter and holds nothing, and a leak under an array a roofer will not warrant.

Scope

Covers pre-install condition and structural reconnaissance on existing residential and light commercial roofs of any covering: asphalt shingle, tile, standing seam and exposed-fastener metal, and low-slope membrane.

Does not cover the shading and geometry survey, which is the site assessment SOP, usually run on the same visit with a separate sign-off. Does not select the flashing method - that is the flashing decision matrix reference. Does not produce a stamped structural calculation; where this finds an undersized or modified framing member, the output is a referral to a licensed structural engineer, not a call made on the roof.

Roles and responsibilities

Procedure

1. Pull the roof's history before the visit. Search the permit record for the last re-roof, ask the customer for the roofing invoice or warranty, and ask directly whether there has ever been a leak, an insurance claim, or a layer added over the old one. Acceptance: an installation year from a document, or an explicit "unknown" written in the record. Wrong looks like a homeowner's estimate recorded as a fact, which is how a 22-year-old roof gets logged as 12. Stop rule: no document and no memory means the roof enters the assessment as unknown age and the physical evidence carries the whole verdict.

2. Survey from the ground before you climb. Walk the full perimeter with binoculars or fly the roof, and photograph each plane. Look for lifted or missing tabs, a visible sag between rafters, moss on the north-facing planes, and the gutters, which hold the granule evidence. Acceptance: every plane photographed from at least two angles, plus one gutter photo showing accumulated granule or the absence of it. Wrong looks like starting on the ladder, which commits you to a roof you have not yet judged. Stop rule: a visible sag, a wave in the deck line, or daylight at the eaves means the roof is not walked at all until the attic has been inspected from inside.

3. Walk each plane and grade the covering. On asphalt, check for granule loss down to exposed fiberglass mat, curled or cupped tab edges, blistering, and nail pops standing proud of the surface. On tile, count cracked and slipped pieces and check whether the underlayment is visible anywhere. On metal, check fastener gaskets and seam integrity. Acceptance: a per-plane grade with a photograph of the worst square yard on that plane. Wrong looks like a single grade for the whole roof, when the south plane weathers years ahead of the north. Hazard: do not walk a tile roof except on the lower third of the pans over battens, because a cracked tile under a boot is both a leak and a fall, and stay off any covering wet with dew until it dries.

4. Probe the deck for soundness at the points that fail first. Press with a flat boot at valleys, at the low course above every penetration, along the eave line, and anywhere the ground survey showed a stain. Acceptance: the deck feels uniformly firm with no give beyond the normal flex between rafters. Wrong is a spongy or dished feel, which is delaminated sheathing under an intact-looking shingle and is the single finding most often ignored because the surface still looks fine. Stop rule: any soft area is marked, photographed, dimensioned off two fixed features, and that plane is red-tagged pending a roofer's opinion; no array is designed onto a plane with an unresolved soft area. Hazard: probe from a position where a foot going through the deck would not carry you off the roof, meaning above the soft spot rather than below it, and with fall protection already connected.

5. Inspect every penetration and flashing detail. Photograph each vent, stack, chimney, skylight and valley, and note the flashing type, its condition, and whether sealant is doing work that flashing should be doing. Acceptance: each penetration photographed and graded, with any inside the planned array footprint listed separately. Wrong looks like grading only the obviously bad ones, when the one that matters is the mediocre one that ends up under 40 modules and unreachable for two decades. Stop rule: a penetration inside the footprint relying on sealant gets corrected before the array goes on, or the footprint moves.

6. Get into the attic. Measure rafter or truss member depth and width and the on-center spacing at three locations, measure sheathing thickness at a vent penetration or cut edge, and identify the framing type. Photograph every water stain, every cut or notched member, and any daylight through the deck. Acceptance: dimensions and spacing recorded from a tape at three points, sheathing thickness measured rather than assumed, framing named as stick-built rafters, engineered trusses, or spaced skip sheathing. Wrong looks like "2x6 at 24 in" written from the first bay. Stop rule: trusses that have been cut or modified, or skip sheathing under the covering, both stop the standard attachment layout and route to engineering, because a truss is a designed assembly and skip sheathing gives a lag nothing continuous to seal against. Hazard: work the attic early, carry water, and put weight only on framing or laid boards; where loose-fill insulation of unknown vintage will be disturbed, that is a respiratory route, so wear a respirator selected under your employer's program per 29 CFR 1910.134 rather than a nuisance dust mask.

7. Establish the attachment and load basis. Record the racking system and pull its engineering letter for this site's design wind speed and exposure category per ASCE 7 in the edition your building department has adopted. Note the required lag diameter, the required thread embedment into the framing member, the pilot hole size, and the maximum attachment spacing allowed. Acceptance: those four values transcribed from the letter for the specific rail and foot being installed, not from a previous job. Wrong looks like carrying last month's spacing onto a house with 24 in framing when the letter's spacing was derived at 16 in. Know which load governs: a flush roof-mount array adds a few pounds per square foot of dead load, which almost never controls, while wind uplift is what sizes the attachment and what the letter is actually about.

8. Give the verdict in bands, then hold the customer conversation. Assign remaining covering life as a range from the evidence in steps 1 through 5, then apply the shop bands: under 10 years remaining, re-roof before the array goes on; 10 to 15 years, present both paths with the removal-and-reinstall labor stated plainly as crew-days that buy the customer nothing new; over 15 years, proceed. Where the range straddles a band edge, take the lower bound, because rounding toward the answer the customer prefers is how a shop ends up removing an array it installed. Acceptance: a written band, a written range, and a dated customer decision. Stop rule: a customer who insists on proceeding under 10 years signs an acknowledgment that removal and reinstall will be at their cost, or the shop declines the work.

The record this produces

One roof assessment sheet per address, attached to the same customer record as the site assessment packet:

• Per plane: covering type, grade, worst-condition photograph, soft-area map with dimensions, red-tag flag.
• Penetrations: type, condition grade, inside or outside the planned footprint, correction required.
• Attic: framing type, member depth and width, on-center spacing at three points, sheathing thickness, stain and daylight photographs.
• Attachment basis: racking system, engineering letter revision, lag diameter, thread embedment, pilot size, maximum spacing, design wind speed and exposure used.
• Verdict: remaining-life range, band, customer decision, date, and any signed acknowledgment.

Design lays out attachments from the framing spacing. The crew lead works from the attachment basis on install day and reports back if the framing does not match. Two years later, if a leak is claimed, the penetration photographs and the deck map say what the roof was before anyone touched it, which is worth more than any argument made from memory.

A worked pass, including the step that failed

Single-story ranch, architectural asphalt shingle, two planes.

Step 1: the permit record shows a re-roof 14 years ago and the customer produces the invoice, one layer, documented. Step 2: perimeter photographs show no sag, moderate granule accumulation in the north gutter, moss on the north plane only. Step 3: the south plane grades fair, even granule loss and no exposed mat; the north plane grades good with moss along the lower two courses.

Step 4 fails. Probing the south plane's valley finds a dished, spongy area roughly 3 ft by 2 ft, centered about 6 ft up from the eave and 18 in off the valley centerline, under shingles that look no worse than their neighbors. The stop rule runs: marked, photographed, dimensioned off the valley and the eave, and the south plane red-tagged pending a roofer's opinion. The assessor finishes the remaining steps, but that plane is out of design until the opinion comes back.

Step 5: three penetrations, two outside the planned footprint and sound; a plumbing vent inside the footprint is sealed with mastic over a failed boot, listed for correction before any array goes on. Step 6: 2x6 rafters, on-center measured at 24, 24 and 24-1/4 in across three bays, sheathing 7/16 in OSB measured at a vent cut, stick-built, and one old stain under the same valley that failed step 4, which corroborates the probe. Step 7: the racking letter for this site's design wind speed calls for a 5/16 in lag with a stated thread embedment and a stated maximum spacing at 24 in framing, all four values transcribed. Dead load runs a few pounds per square foot over roughly 460 sq ft across 20 attachment points, which is not what governs; the uplift case in the letter is.

Step 8: the evidence puts remaining life at 8 to 12 years. The range straddles the 10-year band edge, so the lower bound governs and the verdict is re-roof first. The customer is shown the valley photograph and the attic stain together and agrees to re-roof both planes before install.

Outcome: no array designed onto a red-tagged plane, a leak found before it was covered by 20 modules, and a re-roof sold on evidence rather than argument.

References

• 29 CFR 1926.501, OSHA construction fall protection; 29 CFR 1910.134 for respirator selection under a written program where attic insulation is disturbed.
• ASCE 7, in the edition adopted by your building department, for design wind speed and exposure category feeding the racking manufacturer's engineering.
• Racking manufacturer engineering letter for the specific rail and foot: lag diameter, thread embedment, pilot size, attachment spacing.
• See related: the site assessment and shading survey SOP, and the tile versus asphalt versus metal flashing decision matrix.