Why a Roof Inspection Waits for a Dry Day, and What Wet Shingles Hide

A roof inspection is set for a Tuesday morning, and the sky over St. Louis is clear, but the shingles still hold last night's rain in the shaded rows and the valleys. Many homeowners wonder why the inspector does not simply climb up and start. The short answer is that wet asphalt shingles are slippery, and a wet surface hides the small signs the walk is meant to find. A careful inspection waits until the roof has had enough sun and air to dry, or it splits into parts that can be checked safely on different days.

Why wet shingles are a safety question first

Asphalt shingles with water on them lose grip quickly, and the pitch of a typical residential slope makes a slip more serious than it would be on a flat driveway. Ladders wet from the rain are a separate hazard at the eave, where the inspector has to step from the ladder onto the roof. An inspector working on a steep slope needs steady footing and a clear view of the next step, and a surface with water sheeting across it takes both away. A walk that is safe for the person doing it is the first condition for the walk to happen at all.

What the wet surface hides

Water changes the look of a shingle. A wet granule surface is darker and shinier, and the sheen of moisture can flatten the texture that shows loss of granules. Hairline cracks along the tab line close up when they are soaked and open again as they dry, so a crack that is easy to see on a dry afternoon can disappear in the middle of a wet morning. A blister can look different when it is damp than when it is dry, and a tab that is curled at the edge may lie down on a wet surface and rise again later. None of these are reasons to skip the walk. They are reasons to schedule it for a dry day and to ask whether the report notes the moisture condition at the time of the visit.

What a dry day lets the inspector check

A dry roof gives the inspector the full picture of the surface. Shingle tabs can be lifted gently to look at the sealant strip and the nail placement. The valleys can be followed without stepping through pooled water. The flashing at chimneys, vent pipes and wall intersections can be read closely, and the photographs come out with the true color of the metal and the sealant instead of a reflection off standing water. Photographs taken on a dry day are also easier to compare with the set from the last visit, because the surfaces show the same color and texture from one year to the next.

The attic is different. An attic check can happen whenever the crew can reach the hatch safely, and it is where wet decking shows itself. A damp spot on the underside of the sheathing that is still wet after a storm is information the roof surface does not give. An inspector may therefore look at the attic first on a wet morning and return to the roof when it dries. Ask whether the plan works that way, and ask who will be in the attic and at what time.

What still gets checked on a wet day

Some of the inspection does not depend on the roof being dry. The gutters and downspouts can be looked at from the ground, including the granule sediment that collects in the trough and the fascia board for paint failure or rot near the joints. The yard can be walked for loose shingle pieces and for the line where water runs off the eave and lands on the soil or the patio. The chimney can be photographed from the ground, and the siding and window trim below the roof edge can be checked closely for staining. A homeowner waiting for a dry day can use the time to walk the yard with a phone and note what the ground shows, which gives the inspector something to compare against when the roof is finally reached.

How to tell a dry roof from a roof that only looks dry

A roof can look dry from the ground after a few hours of sun while the north slope and the valleys stay damp. The shaded side of a house holds moisture longer than the sunny side, and the lower rows of shingles near the eave can still be damp when the upper slope has dried. Valleys, where two slopes meet, often stay wet after the open field of the roof is dry, because water collects there and the sun reaches the bottom of the valley last. Moss and algae growth on a shaded slope also stays damp, and an inspector may choose to avoid those areas until they dry. Ask the inspector which slopes were dry at the time of the walk, and check that the report says so slope by slope.

Winter mornings add a different risk

In a St. Louis winter, a damp morning can turn into a glazed surface when the temperature drops after sunrise. Frost on the shingles or a thin skin of ice at the eave can make the walk unsafe even when the rain has stopped the night before. The freeze and thaw cycle that moves water in and out of the upper layers of the shingle also means that a surface that looked sound on a dry October afternoon may show different wear after a wet January. An inspection scheduled in cold weather should be treated as a walk that may be split, with the attic and the ground checked first and the roof checked when the surface is safe to stand on.

What it costs, and what to ask

The visit itself is the first cost, and the cost of a second trip is the one that surprises people. If the walk is postponed because of rain or frost, the homeowner should know whether the rescheduled visit carries a fee and whether the first visit was counted as complete. Ask whether the first visit is free and what a rescheduled visit costs, and get both answers in writing before the day is set. Call (314) 220-2333 before the appointment and ask what changes if the morning is wet.

• Will the walk wait for a dry roof, and what counts as dry for each of your slopes?
• If the morning is wet, will the inspector check the attic and the ground first?
• Will the report record the surface condition at the time of the visit?
• Which slopes will be skipped if they are still damp, and when will they be checked?
• What does a return visit cost, who schedules it, and is it in writing?

When the report comes back

A report written after a damp walk should say which areas were not walked and why. A blank line where a slope should be is a gap, not a clean result, and it should be read as one. Compare the photographs with the last set you have on file, and look for the same detail on the same slope. Read the report line by line and ask about any area marked as not checked. The report is the record you keep for years, and an honest note about what could not be seen on a wet day is part of that record. If a slope was left for a later visit, the report should name the date that visit was set, and you should write that date down before the inspector leaves.