Why Is My Pool Screen Sagging?

Screen mesh does not stretch or sag on its own. What sags is the tension holding it in the frame, and that tension lives in the spline — the rubber cord wedged into a channel around the panel's perimeter, pinning the mesh edge in place. When spline hardens, shrinks, or backs partway out of its groove, the panel it was holding goes slack. That is what a sagging panel actually is: a spline failure wearing a mesh problem's clothes.

Three things make it happen faster:

• Old spline goes brittle. Rubber spline that has spent years in Florida sun hardens and shrinks rather than staying pliable, and a shrunk cord no longer fills its groove.
• A widened groove. On a cage that has already been rescreened once — common on anything built before the 1980 Casselberry median — an over-driven spline tool can permanently widen the channel, so even fresh spline sits loose in it.
• Roof panels sag under their own geometry. A roof panel has gravity working against the spline in a way a vertical wall panel does not, so the same groove wear shows up there first.

A single sagging panel is a spot repair. Sagging spread across several panels or more than one wall usually means the groove itself is worn out, in which case re-tensioning one panel at a time just moves the problem — see rescreen vs. repair.