Sheathing Strength Axis
Why a structural sheet's long dimension has to run across the rafters or joists it spans, and what happens to the deck when it doesn't.
Straighten Fascia on Raised-Heel Trusses With Offset Blocks and a Gauge Scrap
With no truss tails to cut to a line, get dead-straight fascia by setting offset blocks at each end, stretching a line between them, and checking the run with a scrap 2x gauge block — kickers hold what you've straightened.
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The Problem
On conventional roof framing you snap a line and cut the rafter tails, and the fascia follows straight. Raised-heel trusses take that away — there are no tails to cut and align, so the fascia lands on whatever the truss ends happen to do. Trusses are never perfect, and over a long run every wander telegraphs straight into the most visible line on the house.
The Technique
The reference has to come from a line, not from the trusses.
- Set an offset block at each end of the run and stretch a string line between them — the blocks hold the string a fixed distance off the fascia face so the fascia itself can't push into the line and lie to you.
- Cut a scrap of 2x stock to match the offset and use it as a gauge block: slide it between the string and the fascia along the run. Where it's tight, the fascia is proud; where it's loose, it's shy.
- Push or pull each spot to the gauge and lock it there with kickers — braces running back to solid framing that hold the adjustment.
- Work the run until the gauge just kisses everywhere. A 59-foot run of fascia can come in straight to a sixteenth this way.
Pro tip: The offset blocks are the insurance in this system. A string pulled tight against the fascia touches whatever bows out and reads as straight anyway — offsetting the line means every error, in or out, shows up as a gap difference you can measure with the gauge.
Safety note: This is eave work — you're moving along the roof edge repeatedly while pushing and prying on framing. Use proper fall protection or scaffolding, and set kickers so they can't spring loose while you're leaning on the run.
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