Just realized I was drilling into fire blocks wrong for years

A fire marshal came by a job site last month and pointed out I was putting my sensor screws right through fire blocking without sealing them. He said that basically ruins the whole fire stop system. Has anyone else had to go back and redo their installs after getting this kind of feedback?

2 comments

2 Comments

alice_hart9d ago

Idk how many guys actually think about the thermal envelope side of it. You mentioned ruining the fire stop but that screw hole is also a straight path for conditioned air to leak into the attic or outside. I've seen it cause ice dams in cold climates because the warm air hits the roof deck right above the fire block. The caulk or sealant has to be fire rated too, not just regular silicone or the marshal will flag it anyway.

jordan_webb9d ago

The Building Science guys at BS+ Beer did a whole breakdown on this. They had thermal imaging showing a row of lights in a ceiling where every single fixture was bleeding warm air into the attic, and the fire blocking was basically worthless once you put a hole in it. @alice_hart you're right about the ice dams - I've seen that exact thing happen on a house in Minnesota where the owner added recessed lights and a few months later had water dripping from the soffits. The marshal here checks for that fire-rated caulk too, they'll make you rip out whatever non-rated stuff you used. I've been using Hilti firestop caulk for years, it costs more but I never have to worry about a callback or a failed inspection. What do you use for sealing those penetrations?