STANDARDS OF PRACTICE
The International Standards of Practice for inspecting the roof system is located at www.nachi.org/sop.
MASTERING ROOF INSPECTIONS
To learn about inspecting roofs, please visit Mastering Roof Inspections.
STONE SLATE ROOF
Slate used for roofing is typically 400 to 600 million years old. Most of the quarries in the US are located in the Northeast; Maine, New Hampshire, Vermont, but also stretch as far south as Virginia. Slate may last anywhere from 50 to 200 years depending on quality.
Inadequate substrate: roof deck should be at least ¾”.
Inadequate overhang: Should be 1¼” minimum.
OBSERVATION
Inadequate sidelap: 3” minimum.
OBSERVATION
Inadequate headlap: 4” minimum.
- Headlap is the amount by which slates in alternate courses overlap;
- Headlap is reduced as roof pitch gets steeper and increases as pitch gets shallower. This is because steeper roofs shed water faster.
Under-driven nails.
Broken slates.
OBSERVATION
Broken slates can sometimes be identified when they slip downhill.
Fastened with 1 nail.
OBSERVATION
Visible fastener.
