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Frequently Asked Questions
Why does a recessed box need a fire rating?
Because it is a hole in a rated wall.
The rating belongs to the built wall.
Cutting a void removes part of it.
A standard box does not replace that.
A plastic one softens and drops out.
Which walls does this apply to?
Any wall with a fire resistance rating.
Separating walls between dwellings.
Corridor walls on escape routes.
Compartment and shaft walls.
If in doubt, ask what the wall is rated at.
How does the box restore the rating?
By filling the void when heated.
Usually an intumescent lining that expands.
Sometimes mineral backing or a steel case.
Often a combination of those.
Tested as an assembly, like a fire door.
Does one product suit every wall?
No, and this is the usual mistake.
It is tested in a stated wall construction.
Single-layer board is not double-layer.
Nor is either one masonry or a shaft wall.
Match the certificate to the wall.
Is installation part of the rating?
Very much so.
Board around it made good and sealed.
As the certificate describes, not by eye.
Pipe penetrations need their own treatment.
A correct box fitted loosely is not rated.
Can boxes go back-to-back?
They should not, in the same stud bay.
Two recesses then meet in the middle.
Making one route through the wall.
Offset them into different bays.
Or check what the maker permits.
Where do the other firestopping products sit?
With the fire protection ranges.
Collars, wraps, batts and sealants.
This box is the plumbing termination.
The penetrations around it are theirs.
The two are specified together.