No Firewall in a Semi-Detached

3/20/2021 at 2:31:25 PM

There is a difference between a 'firewall' and a 'fire separation'. A firewall means a wall constructed of concrete or concrete block and has a higher rating (typically 2 hours).

What you require is a fire separation. If both units are on the same lot you are permitted to achieve the fire separation by applying a fire rating to the ceiling. If there is a property line separating them then you require a continuous vertical separation through to the underside of the roof.

Spray foam (referred to as 'foamed plastic' insulation in the Code) is combustible + hazardous and does not benefit a fire separation; in fact unless in a concealed space it also requires protection from exposure to fire.

What you need is a wall inside your attic together with 5/8" drywall. The wall needs to be constructed in such a way that a collapse on one side wont mean the wall is compromised (thus you may require 2 walls). Roxul or fiberglass insulation inside the wall benefits the fire resistance rating slightly.

3/20/2021 at 7:03:43 PM

spray foam has to be firer rated and you need 5/8 firer rate drywall on both side in the attic .you should take care this matter .

3/21/2021 at 12:35:34 PM

Irene, the previous two contractors have answered your question. So, the short answer is NO. Don't skimp on this one because fire limitation is a major safety concern. Have it done correctly.

3/21/2021 at 6:04:38 PM

Thank you Ian, Manny and Mark. I greatly appreciate your expertise on this matter. I will call a local contractor to have this resolved correctly.

3/22/2021 at 11:27:03 AM

Hello Irene,

Its odd that a semi of that age does not have a brick fire wall separation.

Every other one we have worked on for the last 40 years did.

Foam not recommended.

Better to get your neighbour on board with sharing costs (they will benefit as well) and just do it right.

Some sound separation can be had by using sound batt (the green insulation) plus resilient channel on entire wall, plus two layers of 5/8" drywall.

The second layer of drywall to have sound resistant glue on the back and very few crews in it.

Means disconnecting stairs if they are on party wall.

Best,

Andrew

PARTEX DESIGN BUILD LTD.

1/11/2023 at 10:38:44 PM

Rockwool for sound and firer proof.5/8Type X drywall has a firer rate.

1/21/2023 at 1:10:39 PM

Spray foam is not the right material.

There are specialized materials for that. Similar to fiberglass insulation plus concrete board each side of new attic stud wall.

Studs can be metal.

Best

Andrew