Gap in fire stop

[Marc M]

Hey Bob,
In reference to the gap in the fire stop; just wondering if you feel this is somewhat excessive?
I though i remember Dale F. saying that the largst gap between the flue and the firestop should be around 1/8-3/16"...did I remember that correct?

[Bob Harper]

From UL 127 7.3.2 Firestop spacers
"...The inside diameter of the firestop opening shall not be more than 1/8 inch greater than the outside diameter of the chimney pipe, including chimney joints and raised projections."

If you measure the chimney at its widest point, which is usually the outer female hub of the section above, it should not be less than 1/8 inch than the actual diameter of the FS opening. You cannot go by crude meansurements in the field but moreover, unless there are signs of someone enlarging this hole then verification of a listing sticker to match that fireplace make and model is all a HI should concern themselves with.

hth

[Marc M]

Very good Bob, excellent info, thank you.