I have to create a 75mm air gap between a joist and the twin walled flue which runs from the stove beneath it. The joist sits below a pitched roof which is made from cement fibre tiles in a single storey side extension. This air gap between the joist and flue is currently 25mm. The 1st photo is taken looking up at the ceiling from below and the second from standing in the room. They show the joist on the right which needs to be moved over to create the 75mm air gap. I've considered doubling up the adjacent joists and boxing the flue in. Would that be a reasonable solution and do you guys have any better ones please? Thanks.
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