Fire extinguisher cabinet installation comes down to three decisions made before anyone cuts drywall: which mounting type the wall can take, what rough opening to frame, and how the tub is fixed. Recessed and semi-recessed cabinets are framed into the wall much like a small window, while surface cabinets simply fix to the face of it.
The order of work matters. On most projects the cabinets are bought while the walls are still open studs, and the openings are framed long before the cabinets arrive. Get the opening wrong at that stage and the choice later is between cutting studs and patching drywall, or sending the cabinets back.
Typical US Sizes and Wall Openings
US practice quotes cabinet sizes in inches, width first. The rough opening runs about 1 in larger than the tub in width and height. Its depth depends on the trim, because the trim decides how much of the cabinet stands proud of the wall.
| Extinguisher | Tub inside (W x H x D) | Wall opening (W x H) | Opening depth by trim |
|---|---|---|---|
| 5 lb | 9-1/2 x 24 x 5 in | 10-1/2 x 25 in | 5-1/4 in fully recessed; 4 in with 1-1/2 in trim; 3 in with 2-1/2 in trim |
| 10 lb | 9-1/2 x 24 x 6 in | 10-1/2 x 25 in | 6-1/4 in fully recessed; 5 in with 1-1/2 in trim; 4 in with 2-1/2 in trim; 2-1/2 in with 4 in trim |
| 20 lb | 12 x 27 x 8 in | 13 x 28 in | 8-1/4 in fully recessed; 7-1/4 in with 1-1/4 in trim; 6 in with 2-1/2 in trim; 4-1/2 in with 4 in trim |
| Two 20 lb side by side | 20 x 27 x 8 in | 21 x 28 in | Same depths as the 20 lb cabinet |
These are the sizes on our fire extinguisher cabinet page and drawings. Other makers' tubs can differ by half an inch or so, so always frame to the figure on the submittal for the cabinet you are actually buying, never smaller.
Match the Cabinet to the Wall Depth
A cabinet can only recess as far as the wall allows. Interior partitions in commercial buildings are often framed with 3-5/8 in steel studs, and smaller buildings with 2x4 wood studs, which measure 3-1/2 in. With one layer of 5/8 in drywall on the face, that leaves roughly 4-1/4 in from the finished face to the back of the stud cavity.
- A thin partition takes a 10 lb cabinet with 2-1/2 in trim (4 in deep opening) or with 4 in trim (2-1/2 in), but not a fully recessed 10 lb cabinet, which needs 6-1/4 in.
- A 6 in stud wall gives about 6-5/8 in, enough for a fully recessed 5 lb or 10 lb cabinet, or a 20 lb cabinet with 2-1/2 in trim.
- A fully recessed 20 lb cabinet needs 8-1/4 in, deeper than either wall, so it needs a furred-out wall, a chase behind it, or a semi-recessed trim.
Measure the actual wall build-up before ordering. Two layers of board, a fire-rated assembly or services inside the wall all change the depth available.
Framing and Fixing the Tub
Manufacturers' installation sheets set out the basics, and they are worth following exactly:
- Frame in above, below and at both sides of the opening while the studs are exposed.
- On a load-bearing wall, double the studs on each side of the tub. If a stud has to be cut to fit the cabinet, install a load-bearing header above the opening.
- Set the tub in the opening, centred and level both ways, and mark the fixing points through the holes in the tub sides.
- Fix the tub at no fewer than four points, at least two of them into framing members. One common specification is #10 x 2-1/2 in self-drilling screws; in masonry, use expansion anchors instead.
- Tighten evenly so the tub is not pulled out of square, then check that the door swings freely. If it binds, shim the tub.
- Fit the glazing clips without over-tightening them, then the handle, the catch and finally the extinguisher.
Trimless cabinets are different: their plaster stops sit behind the board, so they must go in before the drywall. And a cabinet in a fire-rated wall has to be a fire-rated cabinet with its own larger opening and its own instructions. We do not make fire-rated cabinets, and we say so rather than quote one.
Stay Inside the 4 in Corridor Limit
In a corridor or any other circulation path, the ADA Standards limit anything with a leading edge between 27 in and 80 in above the floor to a projection of 4 in. Fully recessed cabinets and most semi-recessed trims pass comfortably. A 4 in trim only passes with a recessed handle, because a standard pull handle adds to the projection, and 4-1/2 in trims and surface cabinets do not pass at all. The same standards keep the handle within reach, no higher than 48 in above the floor.
Set the mounting height from the extinguisher, not the cabinet: NFPA 10 governs where the top and bottom of the extinguisher may sit, and our fire extinguisher cabinet page gives the figures. Our fire extinguisher cabinet CAD drawings show the wall opening, trim projection and mounting height on every sheet, so the framing crew and the fire engineer work from the same numbers.
A fire extinguisher cabinet that is framed to the right opening, fixed into framing and kept within the corridor limit goes in quickly and passes inspection. One that arrives before anyone has checked the wall depth tends to end in cut studs and a patched wall.