What Is Built-In Cubby Concealment Geometry? (Stud Spacing)
Built-in cubby geometry is the set of dimensions and clearances that let a recessed cabinet fit inside a stud bay without cutting the studs. At 16 inches on center, the nominal opening is 14.5 inches wide; at 24 inches on center, it is 22.5 inches. Measure the actual bay, check the wall’s purpose and services, then size and finish the cubby to suit.
Could you make a recess that fits neatly between studs and still preserve the wall’s structure, wiring access, and fire protection? The key is to treat stud spacing as a starting point, not a finished measurement. I plan a cubby around the real opening and the wall’s function, then verify every clearance before cutting the wall finish.
Plan the Stud Bay and Wall Function
Stud-bay geometry describes the usable space between framing members, plus the depth available behind the wall finish. The nominal spacing helps locate a possible opening, but does not set the cubby’s final size. Before planning the box, identify the wall type, its purpose, and what may occupy the cavity.
“On center,” or OC, is the distance from the center of one stud to the center of the next. A common stud is 1.5 inches wide, so a typical bay at 16 inches OC has a nominal clear width of 14.5 inches. At 24 inches OC, the nominal clear width is 22.5 inches.
Those figures are useful for rough planning, not fabrication. Studs may be bowed, doubled, irregularly spaced, or covered by layers of finish. Measure the clear opening at the intended height and at more than one point. If the studs lean or the opening narrows, use the tightest measurement when sizing the cubby.
First establish what the wall does. It may be load-bearing, part of a braced-wall panel, a fire-resistance-rated assembly, or a wall that separates spaces with special requirements. A recess can affect these functions even when it fits between studs. If you cannot confirm the wall’s role from plans or site records, ask the local building official or a qualified design professional before proceeding.
I use a simple rule during layout: the wall function sets the limits; the measured bay sets the cubby size. Do not plan to notch, cut, or drill a stud just to gain a little more width. That changes the framing design and may require approved structural details.
Check Depth, Services, and Required Clearances
Wall depth means the framing depth, not the guaranteed storage depth. A standard 2×4 has an actual depth of 3.5 inches, while a 2×6 is 5.5 inches deep. Drywall, backing, uneven surfaces, wires, pipes, and other items reduce the space a cubby can safely use.
| Framing | Actual framing depth | What the figure tells you |
|---|---|---|
| 2×4 | 3.5 in. | Maximum framing depth before finishes and obstructions |
| 2×6 | 5.5 in. | Greater nominal depth, still subject to services and finishes |
Check both sides of the wall before opening it. Look for electrical devices, plumbing fixtures, vents, ducts, and signs of repair. Use suitable detection tools, but do not treat a scanner as proof that a bay is empty. If the location is uncertain, inspect through a small opening in a safe, suitable spot or have a qualified trade professional assess it.
Map the location of wires and pipes before setting the cubby depth. The box must not pinch, damage, or trap a service. Keep junction and device boxes accessible. NEC 314.29 requires covered boxes to remain accessible; a cubby, fixed panel, or stored contents must not make a box inaccessible. Confirm the locally adopted NEC edition and the exact conditions with the authority having jurisdiction.
There is no universal airflow rating for an unvented storage cubby. That does not make every location suitable. Do not cover HVAC supply registers, return grilles, or required ventilation openings. Check the mechanical design and the instructions for nearby appliances before choosing a location or adding a door.
Fit and Finish Without Cutting Studs
A fit allowance is the small gap between the cubby’s outside edges and the measured opening. It gives room to position the box and account for finish variation. As a practical installation allowance, make the cubby at least 1/8 inch narrower on each side than the measured opening. This is a fitting guideline, not a code rule.
Use the smallest reliable opening measurement for the calculation:
Cubby outside width = measured clear width − 1/4 inch minimum
For example, if the narrowest measured opening is 14 3/8 inches, subtract 1/4 inch. The cubby’s outside width should be no more than 14 1/8 inches under this allowance. Check the top, middle, and bottom; do not assume the bay is square.
| Bay or condition | Nominal clear width | Example cubby outside width* | Next check |
|---|---|---|---|
| 16 in. OC, 1.5-in. studs | 14.5 in. | 14.25 in. | Measure the actual opening |
| 24 in. OC, 1.5-in. studs | 22.5 in. | 22.25 in. | Confirm stud type and finish |
| Measured opening of 14.375 in. | 14.375 in. | 14.125 in. | Use the narrowest measurement |
*Examples subtract 1/4 inch total, or 1/8 inch per side. Actual dimensions govern.
Measure the usable depth from the finished wall face to the nearest obstruction, not from the stud face alone. Then subtract the material needed for the cubby’s back and any planned door or trim. Keep the box within the clear cavity; do not force it into contact with wiring or plumbing to gain depth.
Retain the existing studs. Fit the cubby to the bay and add only the backing or top and bottom blocking needed for the box and its expected load. Choose attachment methods that suit the materials and load. Do not assume the drywall alone can support a loaded box. Where the proposed blocking or attachment could affect framing, confirm an acceptable detail before installation.
Finish the opening so joints are neat and edges are secure, but do not assume trim or a patch restores a wall’s original rating. The correct finish depends on the wall assembly and its listed details.
Verify Access, Fireblocking, and Wall Performance
Fireblocking limits the movement of fire and smoke through concealed spaces. A cubby can interrupt existing fireblocking or alter a rated wall, even when it occupies only one stud bay. Before closing the opening, check the assembly requirements and restore any affected protection using an approved detail.
IRC R302.11 addresses fireblocking, and IRC R302.4 addresses penetrations of fire-resistance-rated assemblies. The relevant requirements depend on the locally adopted code and the specific wall assembly. Ordinary drywall patching is not proof that a rated assembly has been restored. Follow the assembly listing or obtain an approved repair detail.
Also check whether the wall is a braced-wall panel. A recess may affect the panel’s required construction or performance. Do not rely on the fact that the studs remain uncut as proof that the wall is unaffected. If the wall’s bracing role or rating is unclear, pause and seek review from the building official or a qualified design professional.
Before closing the wall, verify these points:
- Existing studs remain uncut and unnotched.
- Wires, pipes, ducts, and boxes are undamaged and remain accessible where required.
- HVAC and required ventilation openings remain unobstructed.
- Fireblocking and any rated-assembly details are preserved or restored as approved.
- The cubby and its support are suitable for the expected load.
- The completed work complies with locally adopted building and electrical codes.
Worked stud-bay examples
These examples show how I apply the measurements; they are planning scenarios, not claims about a specific completed installation. In each case, the measured opening and wall function matter more than the nominal spacing. A good fit does not by itself establish code compliance.
Example 1: A clear 16-inch-OC bay. The nominal opening is 14.5 inches, but the actual gap measures 14 3/8 inches at its narrowest point. Subtracting 1/4 inch gives an outside cubby width of 14 1/8 inches. Before building, verify the opposite side, check the cavity for services, and confirm that the wall is not part of a rated or braced assembly.
Example 2: A 2×6 wall with a device box. The framing depth is 5.5 inches, but a device box occupies part of the planned recess. The box must remain accessible under NEC 314.29. The cubby cannot cover it or leave it reachable only by removing fixed construction. A different bay or location may be needed.
Example 3: A rated or braced wall. The measured bay is wide enough, yet the wall has a required fire or bracing function. In this case, the fit calculation is not permission to proceed. Get the applicable assembly detail or professional review before opening or altering the wall.
Frequently Asked Questions
These answers summarize the basic geometry and the checks that control a safe installation. Local code adoption, wall design, and site conditions can change what is allowed. Treat the measurements below as planning guidance, then verify the actual bay and applicable requirements.
How wide is a stud bay at 16 inches on center?
The nominal clear width is 14.5 inches when studs are 1.5 inches wide. Measure the actual opening before sizing a cubby.
How wide is a stud bay at 24 inches on center?
The nominal clear width is 22.5 inches with 1.5-inch-wide studs. Actual framing may differ, so measure the bay.
How much fitting clearance should I allow?
As a practical allowance, make the cubby at least 1/8 inch narrower on each side than the measured opening. This is not a code-mandated tolerance.
How deep is a 2×4 wall cavity?
A standard 2×4 has an actual framing depth of 3.5 inches. The usable cubby depth is less after finishes, the box back, and any services or obstructions are considered.
Can I cut a stud to make a cubby wider?
Do not cut, notch, or drill studs to enlarge the opening without an approved structural design and code-compliant detail. The guidance here is for a cubby that fits between existing studs.
Can a cubby cover an electrical box?
No. NEC 314.29 requires covered junction and device boxes to remain accessible. Confirm the locally adopted code and ensure the cubby does not block access.
Does every storage cubby need ventilation?
There is no universal airflow requirement for an unvented storage cubby. It must not obstruct HVAC registers, returns, or required ventilation openings.
Can I install one in a rated wall?
Only if the work follows the applicable listed assembly or an approved detail. A standard drywall patch should not be assumed to restore a fire-resistance rating.
Does leaving the studs intact guarantee the wall is safe?
No. The wall may have fireblocking, a bracing function, or other requirements that a recess can affect. Confirm its role before work.
What is the safest first measurement?
Measure the clear space between the studs at the top, middle, and bottom of the proposed cubby. Use the narrowest reliable measurement for the outside width.
(This article was written by one of our staff writers, Garrett Vance. Visit our Meet the Team page.)
