3.7 Sleeves, Cores, Slots & Surface Raceways

Sleeves, Cores, Slots & Surface Raceways

Backbone cable has to get from floor to floor and from room to room, and horizontal cable has to reach outlets on surfaces with no cavity behind them. Two blueprint tasks cover that work: install sleeves, cores, and slots and install raceways. Both are pathway-forming activities, and both are heavily inspected because both create openings in the building.

1. Sleeves, Cores, and Slots Defined

+-----------------------------------------------------------------------------+
|                 PENETRATION TYPES THROUGH WALLS AND FLOORS                  |
|                                                                             |
|  [CORE]   A round hole drilled or cast through a wall or slab. By itself it |
|           is just a hole - it has no lining and no fire rating.             |
|                                                                             |
|  [SLEEVE] A short section of conduit (commonly 4 in EMT or RMC) set in a    |
|           core, with bushings on both ends. Lines the opening, protects the |
|           cable, and gives the firestop system something to seal against.   |
|                                                                             |
|  [SLOT]   A rectangular framed opening through a floor or wall, used where  |
|           cable volume is too high for round sleeves - typically at the TR  |
|           riser wall. Fitted with a curb and a listed firestop system.      |
+-----------------------------------------------------------------------------+

Sleeve Construction Rules

1. Material and size. Riser and wall sleeves are typically 4 in (103 mm) trade size rigid metal conduit or EMT, though 2 in and 3 in sleeves are common for smaller pathways.
2. Extend above the finished floor. A sleeve through a floor is extended above the finished floor — commonly 1 to 3 in (25 to 75 mm) — so that mopping water, a spilled drink, or a sprinkler discharge cannot run straight down the sleeve into the room below. The same principle drives the curb around a floor slot.
3. Bushings on every end. An unbushed conduit end is a knife. Fit an insulating bushing, grommet, or a listed bell end on both ends of every sleeve before a single cable is pulled. This is the same requirement stated for conduit stubs in Section 5.1.
4. Fill and bend radius. Sleeve fill follows the conduit rules from Section 3.2 — 53% for one cable, 31% for two, 40% for three or more — and the cable's bend radius as it enters and leaves the sleeve still governs.
5. Firestop after cabling, and after every change. A sleeve through a rated assembly is a through-penetration. It gets a listed firestop system per Section 4.1, and that system is re-established every time cable is added or removed.
6. Bond metallic sleeves. A metallic sleeve is a conductive pathway component and is bonded to the telecommunications grounding system per Section 4.3.

Sizing the Penetrations

ANSI/TIA-569-E sizes backbone penetrations from the usable floor area served and the projected cable volume, not from the number of drops on day one. A widely used commercial design baseline provides three 4 in (103 mm) sleeves per telecommunications room, with additional sleeves or a floor slot added as the served area and cable count grow. Always confirm the count against the project's Division 27 specification and the engineer's riser diagram before ordering.

[!TIP] Install spare capacity while the hole is open. The labor and the permitting to core a slab is the expensive part; the sleeve itself is inexpensive. Installing a spare sleeve during rough-in, capped and firestopped, is the single highest-value future-proofing decision on a riser.

2. Surface Raceway (Surface Metal and Nonmetallic Raceway)

When a wall has no cavity — masonry, poured concrete, structural glass, historic plaster, or an existing finished wall the owner will not let you cut — the pathway goes on the surface.

+-----------------------------------------------------------------------------+
|                   SURFACE RACEWAY SYSTEM COMPONENTS                         |
|                                                                             |
|   [BASE CHANNEL]     Screwed or adhered to the wall; holds the cable        |
|   [SNAP-ON COVER]    Removable; allows adds and moves without re-pulling    |
|   [DIVIDED BASE]     Fixed barrier separating power from telecommunications |
|   [INTERNAL ELBOW]   Direction change INTO the wall plane                   |
|   [EXTERNAL ELBOW]   Direction change OUT of the wall plane                 |
|   [FLAT ELBOW]       Direction change WITHIN the wall plane                 |
|   [RADIUS FITTING]   Large-sweep fitting that preserves cable bend radius   |
|   [DEVICE BRACKET]   Holds keystone jacks or receptacles in the raceway     |
|   [ENTRANCE END FITTING] Bushed transition into a wall, box, or conduit     |
+-----------------------------------------------------------------------------+

Selection and Installation Rules

• Use the system's own fittings. Surface raceway is listed as a system. Mixing manufacturers, or field-cutting a miter instead of using an elbow, voids the listing and — more practically — produces a sharp interior corner that violates the cable's bend radius. Category 6 and 6A runs specifically require the radius or large-capacity fittings, not the shallow decorative elbows sized for telephone wire.
• Size for growth. Fill the raceway to the 40% design target discussed in Section 3.2, leaving room for future adds. Manufacturer capacity charts state cable counts by category directly — use them, because a 0.30 in Category 6A cable eats a raceway far faster than a 0.20 in Category 5e cable.
• Divide power from telecommunications. Where a raceway carries both, use a factory-divided two-channel base with a fixed barrier. Do not run power and communications loose in a single undivided channel.
• Mount to the structure, level and continuous. Fasten at the manufacturer's stated interval into anchors appropriate to the substrate. Keep the base tight to the wall; a gap lets the cover pop and pinches cable at the joint.
• Bond metallic raceway. Surface metal raceway is bonded and made electrically continuous across every joint, exactly as cable tray is in Section 3.4.
• Respect the raceway's listing at penetrations. Surface raceway is not a substitute for a sleeve. Where the pathway must pass through a wall or floor, transition into a bushed sleeve or conduit stub and firestop the penetration.
• Multi-outlet assemblies (raceway with integral outlets at fixed intervals) follow the same rules and are common along laboratory benches and classroom perimeters.

3. Field Scenario: Historic Masonry Retrofit

[!NOTE] Scenario: A tenant is fitting out the ground floor of a 1920s masonry building. The perimeter walls are solid brick with plaster applied directly to the masonry — there is no stud cavity anywhere on the exterior wall. Twelve Category 6A work area outlets are required along that wall, fed from a new TR at the center of the floor plate. The 2-hour rated corridor wall separates the TR from the tenant space.

Execution:

1. Riser and wall penetration: A single 4 in (103 mm) RMC sleeve is cored through the rated corridor wall at ceiling height, bushed on both ends, and left uncabled until the pull is complete.
2. Pathway to the wall: Cable is routed overhead on wire basket tray to a drop point at the end of the masonry wall, per Section 3.3.
3. Surface raceway selection: Twelve Category 6A cables at 0.30 in OD are counted against the manufacturer's capacity chart. A divided-base surface metal raceway sized for a 40% design fill is selected, with radius internal and external elbows at every direction change rather than standard elbows.
4. Transition: A bushed entrance end fitting takes the bundle from the ceiling drop into the raceway base. Device brackets hold keystone jacks at 18 in AFF, matching the electrical datum on the adjacent wall.
5. Bonding: The metallic raceway is made continuous across every coupling and bonded to the TR secondary bonding busbar with a 6 AWG conductor.
6. Firestopping: After the pull, the corridor wall sleeve is packed with compressed mineral wool and sealed with a listed intumescent sealant to the depth stated in the UL system, and the penetration is tagged with the system number.
7. Certification: All twelve permanent links certify with margin. The radius fittings, not luck, are why the Return Loss results are clean at the direction changes.