National Home Inspector Exam (NHIE) Roof Systems Summary

The granules on asphalt shingles protect the asphalt from the sun's UV rays. As a roof ages, granules wash off and collect in gutters and at downspouts. Bare or smooth patches mean the shingles are wearing out and may need replacing soon.

Wrong choices

• The roof was installed very recently: A new roof may shed a few loose granules, but heavy loss means wear.
• The attic is too cold: Attic temperature does not knock granules off shingles.
• The flashing was installed too tightly: Flashing has nothing to do with granule loss.

Where a sloped roof runs up against a wall, short L-shaped pieces of metal are woven in with each course of shingles. This is step flashing. The siding or counterflashing laps over it. Missing or poorly installed step flashing is a common source of leaks.

Wrong choices

• Drip edge: Drip edge goes along the eaves and rakes, not along a sidewall.
• Ridge cap: Ridge cap shingles cover the peak of the roof.
• Gutter apron: A gutter apron directs water into the gutter at the eave.

Standards of practice let inspectors decide not to walk a roof that is steep, wet, fragile, or otherwise unsafe. The roof can be viewed from the ground (often with binoculars), from a ladder, or by other safe means. The report should state how the roof was inspected and any limits.

Wrong choices

• Walk the roof anyway, because walking is always required: Standards do not require unsafe actions.
• Skip the roof and leave it out of the report: The report should say how the roof was inspected or why it was not.
• Remove shingles to look at the roof deck: Inspections are non-invasive; removing shingles is not required.

As asphalt shingles age, they dry out and shrink, so edges cup up or tabs curl. Heat build-up from a poorly ventilated attic speeds this up. Curled shingles can blow off and let water get under them.

Wrong choices

• Correct nailing on a new roof: Correct installation should give flat shingles, not curling ones.
• A roof that is well ventilated and new: A new, well-ventilated roof should lie flat.
• Gutters that are too large: Gutter size does not make shingles curl.

Drip edge is a bent metal strip at the eaves and rakes. It carries water past the edge of the roof sheathing and fascia so the wood does not wick up water and rot. It also helps water drop into the gutter.

Wrong choices

• To hold the gutters up: Gutters are held by hangers or straps.
• To ventilate the attic: Drip edge is not a vent.
• To keep snow on the roof: Snow guards do that, not drip edge.

Where a lower roof edge ends against a wall that continues past it, water running down the step flashing can pour behind the siding. A kickout (diverter) flashing at the bottom turns this water out into the gutter. Missing kickouts often cause hidden rot in the wall below.

Wrong choices

• Seals around a plumbing vent pipe: That is a pipe boot or vent flashing.
• Holds the ridge cap shingles in place: Ridge caps are nailed; kickout flashing has nothing to do with them.
• Connects the bathroom fan duct to the roof: That is a roof jack or vent cap.

When gutters fill with leaves, water spills over the edge. It can rot fascia and roof edges, stain siding, form ice in winter, and soak the soil next to the foundation. Gutters should be cleaned regularly.

Wrong choices

• Better drainage because water spreads out: Overflow puts water where it causes damage.
• Lower attic temperatures: Gutters do not cool the attic.
• Stronger shingles: Gutters have no effect on shingle strength.

Warm air leaking into the attic heats the roof deck and melts snow. The water runs down to the cold overhang and freezes, forming a dam. Water then backs up under the shingles and leaks inside. Air sealing, insulation, and ventilation help prevent this.

Wrong choices

• Too much attic insulation: Good insulation helps prevent ice dams by keeping heat out of the attic.
• Gutters that are too large: Gutter size does not cause ice dams.
• Shingles installed in summer: Installation season does not cause ice dams.

Rubber collars on plumbing vent flashings dry out and crack from sunlight, often before the shingles wear out. Rain then runs down the pipe into the attic. Look for stains on the roof deck around the pipe from inside the attic.

Wrong choices

• Sewer gas will enter the kitchen: The collar keeps out rain; it does not seal the drain system.
• It will block the vent pipe: A cracked collar does not block the pipe.
• It lowers the water pressure: Vent flashings have nothing to do with water pressure.

Asphalt shingles shed water by gravity and overlap. Under common model codes, they are typically allowed on slopes of 2:12 or steeper, and slopes from 2:12 up to 4:12 need double underlayment. On flatter roofs, water backs up under the shingles and leaks.

Wrong choices

• 4 in 12 (4:12): Shingles can typically go on slopes from 2:12 up to 4:12 with extra (double) underlayment.
• 1/4 in 12: 1/4:12 is a typical minimum for some low-slope membrane roofs, not shingles.
• 6 in 12: Shingles are commonly used on slopes much lower than 6:12.