I am planning to glaze an old diamond oak mullion window in my house and want to do it in such a way that it is as waterproof as possible and as attractive as possible which calls for a compromise
Most waterproof is one sheet of glass on the exterior of the mullions
Prettiest is glass between the mullions but I have been warned off this option by several people cos it tends to leak
So what I shall do is have several panes of glass, set into a new oak frame which is external to the mullions but as close to it as possible. The division between the panes of glass will be a shaped oak bar which lines up with a mullion, so from the outside it looks somewhat like a new mullion (luckily its at first floor level)
Cue ascii art of exploded cross section of mullion and bar ...
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