Help! I am starting my second attempt at a redwood gate. Arched top rail (long grain) with rails & stiles that frame loose slats in a groove in the rails & stiles. The gate opening is 39”. Location Napa, CA. All the rain comes between Dec to March then dry for the rest of the year with very dry summers.
The 1st attempt was with horizontal long-grained arched top rail half-lap glued to long grain stiles = long-grain to cross grain. As I should have known the cross-grains split with swelling when soaked in winter rains. The next try will use full length stiles with mortise & tenon into the rails.
1. How much expansion should be expected for overall width with redwood, meaning how much gap is needed per side of the opening; 1/2” per side?
2. For the floating slats would opposing rabbit or tongue & groove joints work better to prevent warping?
3. How can the swelling for either junction be predicted? I am concerned about tongue swell splitting out grooves.
4. If I use 1×6 slats what width groove in stiles and rails would be needed when wet to prevent split out?
5. Are there tricks with glued exterior mortise & tenon joints to prevent split out when they expand in the rain, meaning just glue the ends or over size the mortise to some degree to allow it to swell?
6. Can all these expansion problems be taken care of with sealing?