We are having a new woodburning stove and the HETAS fitters have belatedly discovered that the existing twin-wall flue passes only 10mm away from the gable end rafters. Having installed the stove they are now refusing to issue a certificate since Approved Document J and the Selkirk twin-wall instructions both specify a 50mm air gap.
They have proposed fitting a smaller diameter flue (6in ID in place of the 9in flue for the original open hearth) but this including storm collar, rain cap and flashing will be a lot of expense.
Is there a fire resistant board which will provide adequate fire protection in a 10mm thickness? As it will only touch the curved outer surface of the flue in one place common sense suggests this is the way to go, but I cannot fiind anything with formal approval for this application.
All suggestions gratefully received!
They have proposed fitting a smaller diameter flue (6in ID in place of the 9in flue for the original open hearth) but this including storm collar, rain cap and flashing will be a lot of expense.
Is there a fire resistant board which will provide adequate fire protection in a 10mm thickness? As it will only touch the curved outer surface of the flue in one place common sense suggests this is the way to go, but I cannot fiind anything with formal approval for this application.
All suggestions gratefully received!