I plan to wire my house with CAT6 cables, running inside the walls (drywall, wood). I would have to drill through the floor and probably through fire blocks in between the studs.

Lot of guides advise to pull a string in addition to the cables, so that additional wires could be easily pulled later. I do want to do that, mostly for upgradability later on

However one guide mentioned to fill the fireblock/floor hole with fire retardant sealant.

If I fill with the sealant, there is no way I could pull anything else through it. So the question is: is it really necessary to fill these holes with fire retardant sealant, or is it safe to leave them as is?

If it matters, I am in Ontario, Canada.

  • Fire caulking may or may not be required if there is unfinished attic above. Ask your local jurisdiction.
    – Kris
    Commented Jul 27, 2015 at 21:46

2 Answers 2


If you don't run conduit, you won't be able to pull wires with a pull string going through holes in studs anyway. So you might as well firestop them (or run conduit and firestop around the outside of it.)

  • And if I have a fully enclosed conduit (like Smurf Tube), does that mean the cables inside of it don't need to be in-wall rated (CL2, Plenum, etc)?
    – Slav
    Commented Jul 28, 2015 at 14:01

Most current US building codes require filling all holes that penetrate floors with fireblock foam. Building inspectors routinely look for it. The purpose is to slow down the spread of fire from floor to floor, similar to the firebreak blocking required in many jurisdictions in every stud bay in framed walls.

This would preclude leaving pull holes and string.

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