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Q. Does a cathedral shed roof addition need collar ties to restrain the outward thrust of the rafters?

A. A shed roof with a proper shear connection at the ridge has no lateral thrust. Think of a ladder leaning against a building. Imagine the ladder has wheels at the bottom. With no restraint at the top, the ladder will roll away from the building. Attach the ladder to the building at the top, however, and it stays put. A shed roof is similar; as long as it’s properly attached at the top, the bottom can’t move. "Collar ties" are an exercise in futility. Use them as ceiling joists if needed; otherwise, leave them out.

—R.R.

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