Find rafters from the roof without guessing

A lag screw that misses the rafter holds almost nothing, and it leaves a hole in your roof. Finding framing is the first skill of a good installer.

1. Measure in the attic. Find a reference both inside and out (a vent pipe or the gable wall) and measure to the first rafter. Rafters are usually 16 or 24 in on center.
2. Read the nail lines. On many roofs you can see slight bumps or rows where sheathing nails hit framing.
3. Use a deep-scan finder designed for roofs, then confirm.
4. Confirm with a pilot hole. A small bit that suddenly bites into solid wood tells you you’re on the rafter. Probe side to side to find its edges and mark the center.

Once you’ve found two, snap chalk lines along the rafter centers across the whole array area. Everything else follows those lines.

Quick answers

What if I miss the rafter?

Seal the hole with the manufacturer-approved sealant, move over, and never leave an open hole under a shingle.