How do you guys keep your interior casing mitres from opening up? I trimmed out a house last winter and was in there today and a lot of the mitres had opened up. Its quite unfortunate because they were all very tight to begin with, and all were glued and nailed together.
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voodoo magic.
Over the years I've glued (Titebond I, II and III) and nailed, bisquited, pocket screwed and splined mitres. One common thing was outside of a few, they have stayed together. A couple things might have helped. Good fitting to begin with (no forcing or stress on the joint). Wait to nail off the perimeter until mitre's are dry. Back up gaps behind the jambs/wall surface or take care of it b/4 timming out When mitres are good, but there's space behind them and the wall-never leave them just flopping around. Shim behind and nail only one side of the mitre. Good nailing along the jambs, spot nailing at the perimeter-enough to keep it from moving around, but not so much as to want to change the fit of the mitre.
What kind of trim/style are you working with.
Another point is to keep nails in the outside edge of the trim to a minimum and avoid nails generally (especially on the outside) within 4-6 inches of the corners (so that the trim can flex).