Truncated Domes
Best Truncated Domes for Retrofit in 2026
Cojo
May 7, 2026
7 min read
The best truncated dome for a retrofit installation is the system that bonds reliably to cured concrete, holds ADA Standards 705.1 dome geometry under traffic, and maintains 70 percent contrast through year 7 minimum. In practice that filter narrows the entire product universe to five families: surface-applied composite panels, surface-applied polymer-concrete panels, polymer mats, surface-installed replaceable cast-iron systems, and stamped truncated-dome retrofit overlays.
This guide ranks the five families by retrofit fit, ADA 705 compliance margin, and lifecycle cost. The list is product-family-level, not vendor-specific. Cojo specifies and installs all five depending on substrate condition and exposure profile.
A retrofit truncated dome has to meet four criteria before it earns consideration.
Cast-in-place panels need wet concrete and are off the table for retrofit. The remaining options either bond chemically (epoxy adhesive on cured concrete) or anchor mechanically (stainless-steel countersunk fasteners) or both. Surface prep matters more than product choice here. The substrate has to be clean, dry, level within manufacturer tolerance, and free of curing compound or sealer.
Dome base 0.9 to 1.4 inches, top 0.45 to 0.9 inches (50 to 65 percent of base), height 0.2 inches, center-to-center 1.6 to 2.4 inches, base-to-base 0.65 inches minimum. Manufacturers publish these dimensions on every spec sheet. Verify the published geometry, not the marketing claim.
Federal yellow on a UV-exposed surface fades. The retrofit market's hard floor is "still 70 percent at year 7," because anything sooner triggers an early ADA 705.5 wear failure and a re-replacement. Cast iron and polymer concrete clear that bar comfortably. Composite plastic clears it on most product lines but margin tightens at year 8 to 10.
Dynamic coefficient of friction at 0.42 minimum (wet) is the industry expectation. ASTM C1028 testing is voluntary on top of ADA 705 but a published number signals a serious manufacturer.
Polymer-concrete panels are the safest all-around retrofit pick. The aggregate-and-resin matrix delivers compressive strength close to portland-cement concrete with the color-fast pigment of a thermoset resin. Panels arrive in 24-inch by 24-inch up through 36-inch by 60-inch sizes and bond with ASTM C881 epoxy plus stainless countersunk anchors at 6-inch on-center perimeter spacing.
Lifespan is 10 to 18 years. Snowplow tolerance is fair to good. Color-fast contrast holds through year 12. The cost-per-square-foot installed sits in the middle of the retrofit range.
Best fit: any concrete-substrate retrofit with a 12 plus year hold horizon and moderate snow exposure.
Replaceable cast-iron systems anchor a permanent stainless-steel-coated frame to cured concrete with mechanical fasteners and seal the perimeter against water intrusion. The cast-iron dome plate bolts into the frame and unbolts for replacement at year 18 to 25.
Lifespan is the longest in the retrofit category at 25 to 35 years for the substrate and 18 to 25 for the dome plate. Snowplow tolerance is excellent. The cost premium is real but lifecycle cost wins in plowed regions.
Best fit: snow-belt retrofit (Bend, Pendleton, La Grande, Hood River), heavy-vehicle path, public-bid project requiring a long warranty.
Composite panels (fiber-reinforced polymer thermoset) are the lowest-initial-cost rigid retrofit option. Bonding is the same ASTM C881 epoxy plus stainless anchors used for polymer concrete. Most major manufacturers ship in ADA 705.1 geometry and 705.2 contrast out of the box.
Lifespan is 7 to 12 years. Snowplow tolerance is poor to fair. UV-driven contrast fade is the typical end-of-life failure mode at year 8 to 10.
Best fit: budget-driven pedestrian-only retrofit, covered or low-UV curb cut, short-hold property.
Mats install fastest of any retrofit option. The flexible polymer or rubber sheet bonds with urethane adhesive plus stainless anchors. Mats conform to slightly out-of-plane substrates that would rock a rigid panel.
Lifespan is 5 to 10 years. Snowplow tolerance is fair, with edge-lift the dominant failure mode. Cost-per-square-foot installed is the lowest in the retrofit category.
Best fit: tight-schedule retrofit (under 2 weeks), compliance-driven retrofit on minor budget, substrate with mild surface irregularity.
A stamped overlay is a thin polymer-modified cementitious topping (typically 0.5 to 1 inch thick) poured over the existing curb-ramp landing and stamped with truncated-dome geometry while the topping is plastic. The overlay cures monolithically to the substrate.
Lifespan is 12 to 20 years when correctly bonded. Snowplow tolerance is good. The catch is that overlay quality depends entirely on the installer because the geometry is created at install rather than factory-cast.
Best fit: large multi-curb-cut retrofit where a single mobilization can cover 8 plus curb cuts, owner-team familiar with stamped concrete work, substrate with good surface profile.
| Retrofit condition | Best system |
|---|---|
| Plowed in winter | Replaceable cast iron |
| Pedestrian only, short-hold property | Surface-applied composite |
| Pedestrian only, long-hold property | Polymer-concrete panel |
| Tight schedule, budget driven | Polymer mat |
| 8 plus curb cuts on same property | Stamped overlay or polymer concrete |
| Loading dock or vehicle path | Replaceable cast iron |
| Substrate slightly out of plane | Polymer mat |
| Public bid, 15 year warranty | Replaceable cast iron |
Industry Baseline Range
| System | Material per sq ft | Installed per sq ft |
|---|---|---|
| Polymer-concrete panel | $42 to $72 | $58 to $104 |
| Replaceable cast iron | $58 to $98 | $76 to $134 |
| Composite panel | $32 to $58 | $46 to $88 |
| Polymer mat | $26 to $48 | $38 to $72 |
| Stamped overlay | $18 to $34 | $32 to $58 (mobilization-dependent) |
Polymer concrete and cast iron each climbed 12 to 24 percent in 2025 on raw-input costs. Composite and mat pricing was more stable. Stamped overlay is the only family where labor (not material) drives most of the variance, and labor pricing climbed 8 to 12 percent across Oregon in 2025. Mobilization charges have grown faster than per-square-foot install rates because crew transport and traffic-control costs now load a higher fixed share onto small jobs.
This article reflects ADA Standards for Accessible Design as of 2026-05-07 and product spec sheets current at publication. Always verify current dimensions, contrast thresholds, and placement requirements with your local jurisdiction and the U.S. Access Board before issuing a final spec. Federal guidance under 36 CFR Part 1191 controls when state or local rules conflict. Product selection alone does not satisfy ADA compliance — installation geometry and 705.2 contrast verification at install are equally controlling.
In March 2026 we retrofit 8 curb cuts at a 22,000-square-foot Hillsboro retail center on a 10-day timeline. Six of the cuts got polymer-concrete panels (long-hold owner, no plow exposure). The remaining two got replaceable cast iron (loading-dock approach with forklift traffic). Same property, two products, two different ADA 705 problems solved with the right family. The lesson is that "best" is conditional. The owner who specs one product across the property is leaving lifecycle dollars on the table.
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