Timber Gate Sag: Diagonal Brace Angle and the Widest Gate That Still Latches After Five Summers

A timber garden gate that sags drops at its latch edge until the latch misses its keep, at which point the gate stops performing any security function at all. This study models sag from stated assumptions: an unbraced ledged gate drops 4.5 W^3 millimetres at width W metres after five seasons, a correctly fitted diagonal brace removes a fraction of that drop peaking at a brace angle of 45 degrees, and a latch tolerates 10 mm of drop. Unbraced, the widest gate that still latches is 1.3 m; braced, it is 1.96 m. At the common width of 1.5 m the brace angle is 35.0 degrees, the unbraced drop is 15.2 mm, and bracing reduces it to 3.1 mm. The brace must run from the lower hinge corner toward the upper latch corner; a brace fitted the other way assists the sag it was meant to prevent. The rule is to brace every ledged gate wider than about a metre and to check the brace direction before checking anything else. SIMULATED, NOT MEASURED.