Sunset
Give me a museum and I'll fill it. (Picasso) Give me a forum ...
It's a 1956 house and when they removed the 2 layers of comp shingles on top and the layer of original wood shingles, all that was left was narrow boards with spaces between them. So, no choice but to do plywood first. The roof was I think 24 squares. Hard to believe they built it that way, but from what I have seen it was typical back then.
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I have a 100+ yr old summer house, it's roof is the board roof. Standard in the old days especially prior to plywood.
It has one advantage: Should a board rot, it means replacement of very little wood which is cheaper.
But it has a big disadvantage, it provides little diagonal stability to the roof, so the plywood replacement will make the roof and building stronger in terms of twisting.
There is also the issue of when nailing, one has to be very concious of the gaps between boards, not something a person with a power stapler/nailer wishes to do.