That being the case, perhaps having the sheeting covering the joists would be better as it leaves a larger air-gap to the tiles for them to continue to dry out as before. Hoovering isn't the point. First off it's dangerous and difficult to hoover up there right now and secondly no room in my house has an open ceiling allowing the wind and rain to blow in! There's a difference between dust and dirt. The attic gets both!
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