What Is In-Wall Rough-In Masonry Concealment? (Brick Chase Specs)
An in-wall rough-in masonry concealment is a nonstructural, brick-faced service chase planned before finish work to route approved wiring, piping, or other services. It must preserve access to boxes and equipment, maintain required clearances and fireblocking, and match local code and approved plans. It is not a hidden storage cavity, and brick dimensions must be verified before layout.
A brick chase can fit a range of home layouts, from a shallow route for approved wiring to a deeper enclosure around services that need more room. The key is to treat it as part of the building system, not as a decorative box added after the fact. I start by identifying what will run inside, what must remain accessible, and which wall, fire, and equipment rules apply.
This guide covers a service chase only. Do not use a chase to hide a storage cavity, bury junction boxes, or cover a service point that needs access. Local code, approved plans, the authority having jurisdiction (AHJ), and the equipment’s listing and instructions control the final design. Rules and adopted code editions vary by location.
Planning the Brick Service Chase
A brick service chase is a nonstructural enclosure that provides a planned route for approved building services. Before setting out brick, confirm the wall’s role, the services’ route, access needs, fire rating, and applicable permits. The approved design must leave enough space for the services and preserve every required clearance and inspection point.
Survey the wall and services
Before construction, identify whether the wall is load-bearing, part of a rated assembly, or both. A chase can add weight, change wall thickness, and affect finishes or openings. Do not cut, notch, or load a structural wall based on a visual guess; get approved details and qualified review where required.
List each service, its actual dimensions, fittings, and likely access points. Include bends, valves, junction boxes, cleanouts, and equipment connections in the layout. Confirm service routes with the relevant trade before closing the wall. A straight pipe or cable may fit on paper, while a coupling, bend, or access panel does not.
Set out brick dimensions accurately
ASTM C216 standard modular brick is nominally 3⅝ × 2¼ × 7⅝ inches. These are reference dimensions, not guaranteed layout dimensions. Actual sizes and tolerances depend on the unit classification and manufacturer, so use the product submittal and a sample brick to set out the work.
A ⅜-inch mortar joint is a conventional modular-brick reference, not a universal code requirement. Brick and joint dimensions affect the layout module: nominal brick length plus a joint is about 8 inches, and nominal brick height plus a joint is about 2⅝ inches. Treat those figures as planning aids only. Confirm actual dimensions and the specified masonry system before laying out the chase.
| Planning item | Reference figure or rule | What to verify |
|---|---|---|
| Modular brick | 3⅝ × 2¼ × 7⅝ in. nominal | Product submittal, classification, and actual unit size |
| Mortar joint | ⅜ in. nominal reference | Specified masonry system and applicable standard |
| Horizontal planning module | About 8 in. using nominal brick and joint | Actual brick length, joint, bond, and end conditions |
| Vertical planning module | About 2⅝ in. using nominal brick and joint | Actual brick height, joint, and course layout |
| Chase depth and clearance | No universal value | Service size, fittings, listing, instructions, and approved drawings |
Do not use a nominal brick measurement as the finished inside dimension of the chase. Allow for the support, mortar, service protection, bends, and any required clearance. Next step: finalize a dimensioned drawing from verified materials and service data before building.
Access, Service Clearances, and Fireblocking
Access and fire protection are design requirements, not finish details. A chase must not make a box, valve, or service point unreachable, and it must not create an unprotected concealed path. Check the adopted code and the equipment’s instructions; there is no single clearance or airflow figure that applies to every chase.
Keep boxes and service points accessible
NEC 314.29 requires outlet, junction, and device boxes to remain accessible without removing part of the building or structure. If a box or service point is inside the chase, provide a suitable access panel at that location. A mortar patch or decorative cover that must be broken or removed to reach the box does not provide practical access.
Plan the opening before laying brick. Check that a person can reach and work on the service point through it, and that the panel does not conflict with trim, fixtures, or nearby equipment. The appropriate panel type depends on the location and wall assembly. Where the assembly is fire-resistance-rated, the access solution must be approved for that construction.
Preserve clearances and fireblocking
There is no universal chase clearance or CFM value. Maintain the clearances and ventilation required by the installed appliance, vent, or equipment listing and manufacturer’s instructions. A passive chase holding ordinary wiring or piping does not gain a generic ventilation requirement just because it is enclosed.
IRC R302.11 requires fireblocking at specified concealed-space locations, including applicable floor and ceiling areas and wall-to-ceiling transitions. The exact detail depends on the adopted code and construction. Check how the chase intersects floors, ceilings, and other concealed spaces; do not assume a masonry face alone closes every path.
A rated wall creates a special design check. An access door or service penetration can affect the rating, while covering a junction box can violate access rules. Use an access assembly and penetration or firestop detail approved for the specific rated construction. Next step: have the access and fireblocking details reviewed before covering the chase.
Chase Support, Masonry, and Finish Execution
A brick face needs an approved support system and a stable base; it should not be assumed to support itself or the services behind it. Keep services protected from mortar, abrasion, fasteners, and incompatible materials. Build to the approved details and applicable masonry standard, rather than relying on a generic wall recipe.
Support the face without changing the structure
Confirm the proposed support, anchorage, base, and added load with the approved plans. The right detail depends on the existing wall, floor, chase height, brick type, and whether the wall is rated. Do not attach masonry to a surface or framing member unless the design allows it. Seek structural review before changing a load-bearing or rated assembly.
Set out the chase from the verified brick and service dimensions. Dry-lay or mark key courses and openings first, especially around access panels and corners. This helps reveal conflicts before mortar makes changes harder. Keep access openings square and sized for the selected panel and the work it must allow.
Protect services during installation
Keep wiring, pipes, and fittings clear of mortar and sharp edges. Use protection and supports required for the service type and installation. Do not fasten through a concealed service route, and do not use the service itself as support for brickwork. Coordinate the sequence with the trade responsible for each system.
| Situation | Design check | Common correction |
|---|---|---|
| Junction box inside chase | Access without removing building material | Place a suitable access panel over the box |
| Rated wall or ceiling | Approved access and penetration details | Use assemblies approved for that rated construction |
| Equipment or vent in chase | Listed clearances and instructions | Revise chase size or route to meet the stated requirements |
| Brick facing at existing wall | Support and added load in approved design | Obtain a reviewed support detail before building |
| Chase crossing floor or ceiling | Fireblocking at required locations | Add the approved fireblocking detail before closure |
These are planning checks, not substitutes for plans, permits, or inspection. Next step: protect and inspect services while visible, then complete the masonry only after required rough inspections.
Inspection and Final Verification
Rough inspection checks work before it becomes hidden by masonry or finish. Confirm required permits and inspections with the local building department, then verify access, service clearances, fireblocking, and penetrations against approved plans. Keep records of concealed work so later repairs do not depend on guesswork.
Use a closeout checklist
Before closure, compare the installed route with the approved drawings and check that each panel opens and provides usable access. Verify that fireblocking and penetrations match the approved details, and that equipment clearances follow the listing and manufacturer’s instructions. Confirm that services operate as intended and that no mortar or debris has entered them.
Photograph concealed routes, supports, fireblocking, and service points before they are covered. Keep product submittals, equipment instructions, permit records, and inspection approvals with the building documents. If a field change affects structure, fire rating, access, or listed clearance, pause and obtain approval before proceeding.
Illustrative installation scenarios
These examples are planning scenarios, not reports of specific completed jobs. They show how the same brick-facing approach can require different details based on the service and the wall.
Scenario 1: A shallow chase for a service route. A homeowner plans a brick-faced route for approved wiring along an interior wall. The installer confirms the cable path and box locations, lays out the brick from the actual product, and puts an access panel at each enclosed box. The route is checked for fireblocking and inspected before closure.
Scenario 2: A chase near listed equipment. A proposed brick enclosure approaches an appliance vent or other heat-producing equipment. The installer does not choose a convenient gap by eye. They check the equipment listing and instructions, revise the chase dimensions as needed, and obtain the required review for any rated-wall or penetration detail.
Scenario 3: A chase crossing a floor line. A route continues through a concealed floor or ceiling area. The design checks where fireblocking is required under the locally adopted code and specifies the detail before the chase is closed. The inspection confirms the work while it remains visible.
The practical lesson is to resolve access, support, rating, and clearance questions on paper first. Next step: request inspection at the required stage and keep the approved details with the project record.
Frequently Asked Questions
These answers give general planning guidance for a brick-faced service chase. They do not replace the locally adopted code, approved plans, equipment instructions, or AHJ direction. When those sources differ from a general reference, the project’s approved requirements govern.
What is an in-wall rough-in masonry concealment?
It is a nonstructural, brick-faced service chase built to route approved building services while preserving required access, clearances, and fireblocking.
Is a brick chase a storage compartment?
No. This guide covers service routing only. Do not use the chase to create a hidden storage cavity or conceal items from required inspection.
What size should a brick service chase be?
There is no universal size. Calculate it from verified service dimensions, fittings, support details, access needs, and any listing or manufacturer clearance requirements.
Are modular brick dimensions exact?
No. ASTM C216 modular brick has nominal reference dimensions of 3⅝ × 2¼ × 7⅝ inches, but actual dimensions and tolerances depend on the specified unit and manufacturer. Check the product submittal.
Is a ⅜-inch mortar joint required by code?
Not universally. It is a conventional modular-brick reference. Follow the specified masonry system and applicable standard, and verify the selected units before layout.
Can a junction box be covered by brick?
Not if that makes it inaccessible. NEC 314.29 requires access without removing part of the building or structure. Provide a suitable access panel at an enclosed box.
Does every chase need ventilation?
No universal airflow or CFM value applies. Follow the listing and instructions for any appliance, vent, or equipment in the chase. Ordinary wiring or piping does not create a generic ventilation rule.
Can I build a chase against a rated wall?
Only with details that preserve the rating, including approved access and penetration or firestop assemblies where required. Confirm the design with the AHJ and approved plans.
What code applies to fireblocking?
IRC R302.11 is a relevant reference for fireblocking in applicable concealed spaces, but the locally adopted code and amendments control. Confirm the required locations and details for the project.
When should the chase be inspected?
Before concealed work is covered, at the stages required by the permit and local building department. Confirm inspection timing with the AHJ and retain photos and approvals.
(This article was written by one of our staff writers, Garrett Vance. Visit our Meet the Team page.)
