Chalk a Line So Finish Fascia Installs Straight Over Imperfect Framing

The Problem

Finish fascia goes on last, over sub-fascia and framing that are never perfect — truss ends wander, sub-fascia dips and humps. Nail the finish fascia to whatever's behind it and it faithfully copies every one of those errors onto the most visible straight line on the building.

The Technique

Give the fascia its own reference instead of trusting the framing.

1. Establish where the top of the finish fascia should land — here, planed out flush with the underside of the roof deck.
2. Mark that spot at both ends of the run.
3. Snap a chalk line between the two marks.
4. Install the finish fascia to the line, not to the sub-fascia behind it. The line is straight even where the framing isn't, so the fascia comes out perfectly straight — and hides every inconsistency behind it.

Everyone does this differently for their own reasons; this is the shed-to-house habit of a carpenter who does it the same way every time, because a two-mark chalk line costs a minute and buys a straight eave.