Divider strips do three jobs at once: they create the panel grid that controls shrinkage cracking, they hide the slab's existing control and expansion joints, and they define the color fields the designer intends. Specifying them well is mostly about material and layout — not about price.
Material options
| Material | Use case | Notes |
|---|---|---|
| White alloy zinc | Default for epoxy and cementitious | Corrosion-resistant, takes polish flush with terrazzo |
| Brass (architectural) | Premium aesthetic, donor-recognition fields | Develops patina; can be lacquered to hold finish |
| Aluminum | Restoration matching only | Will oxidize and turn dark under standard polish — not for new work |
| Plastic/PVC | Not recommended for commercial | Fails under thermal cycling, loses bond |
| Heavy zinc bar | Over slab expansion joints (3/8" wide) | Acts as the terrazzo expansion joint above the slab joint |
White alloy zinc is the right answer for over 90% of projects. The metal is corrosion-resistant, takes the grinding polish flush, and disappears visually into a typical aggregate field. Brass is appropriate when the design calls attention to the divider — donor walls, brand logos, accent lines through a lobby.
Gauge selection
- 14-gauge (0.078" thick): default for epoxy terrazzo and cementitious commercial fields.
- 16-gauge (0.062" thick): acceptable for light commercial and residential.
- 12-gauge (0.105" thick): heavy traffic, industrial settings, or where dividers carry mechanical impact.
- Heavy bar (3/8" thick × full depth): expansion joints over slab expansion joints.
Going below 14-gauge in a commercial environment is false economy. Thinner strips can bow under the grinding load and need replacement during repair — and replacement means cutting them out and patching the field, which is far more expensive than the gauge upgrade would have been.
Depth and anchorage
Strip depth must match the system thickness:
- Epoxy terrazzo (3/8" system): 3/8" strips with L-leg anchor.
- Bonded cementitious (5/8" system): 5/8" strips with L-leg anchor.
- Sand-cushion (2-1/2" system): 2-1/2" strips, full-depth, with engineered anchor.
- Monolithic (1/2" system): 1/2" strips.
Strips include an L-shape anchor leg at the base that sets into the underlayment adhesive. On bonded systems the leg is bedded in epoxy adhesive applied to the substrate; on sand-cushion the leg sits in the underbed mortar.
The three layout rules
Rule 1 — Over every slab control and construction joint
The terrazzo cannot bridge a slab joint that is going to move. Any control joint, construction joint, or expansion joint in the substrate must have a divider strip directly above it, isolated from the field on both sides. For expansion joints, use a heavy bar strip with a sealant reservoir — not a standard divider.
Rule 2 — At every column line
Columns are structural movement points. The strip pattern should run through each column line, with the column itself treated as an interrupting element, sleeved with a divider strip around its base.
Rule 3 — Subdivide fields larger than 6'×6'
For epoxy systems, panels larger than 6'×6' will shrinkage-crack across the field. The grid spacing is part of how the system works, not an aesthetic add-on. For cementitious systems the limit is more generous (10'×10') but the principle holds.
Design layouts that work
The divider grid is the floor's organizing logic. Three patterns recur across well-designed terrazzo projects:
- Orthogonal grid aligned to architecture — strips run parallel and perpendicular to the building's primary axes, with grid lines passing through columns and dropped ceiling reveals.
- Radial layout from a center point — appropriate for rotundas, lobbies with a feature drum ceiling, and circular brand graphics.
- Designed-pattern layout — strips form a pattern (logo, geometric motif, wayfinding lines) that is itself the design statement, with field color fills between the lines.
Mistakes to avoid
- Specifying a divider layout that ignores the slab's existing joints. The terrazzo will crack along the slab joints regardless.
- Using PVC or plastic strips in a commercial environment. They fail under thermal cycling and don't hold paint or polish.
- Random divider layout that's neither orthogonal nor designed. Reads as accidental and ages poorly.
- Sub-6' panels at building entries where stretchers and luggage carts hit the strip edges repeatedly. Plan the entry zone with a heavier-gauge divider.
- Brass strips in a wet zone without lacquer or wax protection. They tarnish unevenly.
Frequently asked
Can divider strips be added after the pour to mask cracks?
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No. Strips are installed before the field pour and the terrazzo is poured against them. Retrofitting strips means cutting out a strip of terrazzo and re-pouring — typically more expensive than just patching the crack.
Are brass strips worth the upgrade?
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On floors where the divider is a design feature, yes. On a hospital corridor where the divider is a service necessity, no. Brass typically adds 10–15% to material cost on the strip line item; expect 1–3% impact on the total system cost.
Do divider strips affect the floor's slip resistance?
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Minimally. The strip is only 1/8" wide at the exposed face, and the surrounding terrazzo carries the foot's contact area. Slip ratings are measured on the terrazzo field, not at the strip line.