Nail Tips in the Attic Tell You Something About the Roof Above

Most homeowners never see the underside of their own roof. The attic is the one place where the roof deck is visible from below, and if you have a hatch or a pull-down stair, it can show you something the shingles hide. Nail tips poking up through the sheathing are one of the most common findings in St. Louis attics, and they are easy to misread. A few tips are normal. A pattern of them is worth asking about.

What the nail tips are

When a crew fastens shingles, each nail goes through the shingle, the underlayment and the roof deck. Most of the time the nail is long enough to bite into the deck and stop there. A tip that shows through into the attic means the nail was longer than the deck thickness plus the bite it needed, or that the deck shifted or shrank around it. In older houses with board sheathing, the tips are often the shank of a nail driven through a board that has since dried and split. In houses with plywood or oriented strand board, the tips usually come from a nail that was driven at the wrong depth or a fastener that was too long for the panel.

The tip itself matters less than what surrounds it. A tip with a little rust or a dark ring around it has been wet at some point. Frost forms on cold metal, and in an attic with weak ventilation, warm moist air from the house meets the cold tip and frost builds up on it. When the weather turns, that frost melts and the sheathing around the nail darkens. After several winters you may see a patch of staining that runs from one nail to the next, which is a different finding from a single tip with no stain at all.

What an inspector looks for

An inspector who goes into the attic will walk the rafters or trusses with a flashlight and look at the underside of the deck in the same order as the roof itself. That means starting near the eave, working up the slope toward the ridge, and noting where the tips cluster. A scattered handful across a large field of sheathing is usually an installation detail that does not need action on its own. A tight group of tips near a ridge vent, a valley or a plumbing vent deserves a closer look, because those spots tend to see the most movement and the most condensation.

Three kinds of photos belong in the record. The first is a wide shot showing the slope and where the tips sit relative to the rafter or truss lines. The second is a close shot of a few tips with a ruler or a pen laid alongside for scale. The third is a shot of any staining, taken so that you can tell whether it is fresh or old. Fresh staining has a softer edge and may still feel damp to the touch. Old staining is dark and dry, and it often has a clear outline that has stopped growing. If the report does not include these three views, ask for them before you make any decision about the roof.

The inspector should also check the sheathing for softness. Press a screwdriver tip gently into the board near a stained area. Sound wood resists. Wood that has been wet through several freeze-thaw cycles will give slightly, or it will crumble at the edge. St. Louis winters swing between thaw and hard freeze several times a season, so a deck can take on water and dry out many times before any shingle on top shows damage. That is why the attic check and the surface check belong in the same visit, and why a clean-looking shingle field does not settle the question by itself.

Ventilation is part of this check too. Look at the soffit intake and the ridge exhaust while you are in the attic. If the soffit vents are blocked by insulation, or if the ridge vent is missing or painted over, the attic will hold more moisture and frost will form on the nails sooner. An inspector who notes the nail tips without noting the vent condition has given you half of the answer.

What it costs

Checking the attic can be part of the same visit as the roof inspection, so it does not always need its own trip. A homeowner who wants the attic checked should ask whether it is included, because some inspections only cover the roof surface. If the attic check is priced as an extra, ask for that price in writing before the inspector arrives. Keys can tell you what the visit includes, and the written scope should list the attic as its own line so you can see whether it was done.

If the sheathing needs replacement, the cost depends on how many sheets are affected and whether the damaged area sits under a slope that is also getting new shingles. Replacing a few sheets during a reroof is a small line item when the crew is already on the roof. Replacing them on a separate day means a second mobilization, and that adds to the bill. Ask the roofer to mark the damaged sheets in the photo set so the cost can be tied to specific boards rather than a general allowance.

What to ask

• Did the inspector go into the attic, and which slopes did they check?
• Are the nail tips in a pattern, or scattered across the field?
• Where is the staining, and is any of it fresh?
• Was the deck pressed for softness, and at which spots?
• Will each stained area be photographed with a scale reference?
• Is replacing damaged sheathing included, or priced as a separate line?
• Who will be in the attic when the new shingles go on, and will they check the tips again?

Ask for the answers in writing and keep them with the rest of the inspection report. If the report says the nail tips are normal and notes nothing else, that is worth confirming with a second look before you decide the roof is sound. If you plan to send the roof report to your insurer, that step is yours to take with your own company. A roofing contractor can document what they see and put a written scope with photos and measurements in your hands, and the conversation with your insurer stays between you and your insurer. To ask about the attic check or the sheathing, call Keys at (314) 220-2333.