Compliance disclaimer: Always verify current requirements with your local jurisdiction. This article reflects 2026-05-07 specifications under ADA Standards 705 and 36 CFR Part 1191. Federal accessibility rules update; state and city codes can be stricter.
Truncated domes are the small, raised circular bumps you feel underfoot at curb cuts, transit platforms, and pedestrian crossings. They are a federally required detectable warning surface that signals a transition from pedestrian space to a vehicle area or a drop-off. Under ADA Standards 705.1 the dome shape, size, spacing, color contrast, and placement are not optional. They are spec, not style.
This guide covers the product side: what truncated domes are, the three install systems Cojo deploys, how the federal dimensions translate into specifying real panels, and how to pick the right system for new construction versus retrofit work. For the parking-stall side of ADA compliance (stall widths, access aisles, signage), see our ADA parking requirements Oregon guide.
What Is a Truncated Dome and Why Is It Required?
A truncated dome is a raised, flat-topped bump installed in a uniform grid across a detectable warning surface. The federal definition lives in 36 CFR Part 1191, which adopts the 2010 ADA Standards for Accessible Design. The shape is engineered to be felt by a person using a long cane or by foot, without becoming a tripping hazard for people who can see.
The 60-word direct answer: Truncated domes are raised circular bumps that meet ADA Standards 705 dimensions (0.9 to 1.4 inch base, 0.45 to 0.9 inch top, 0.2 inch height, 1.6 to 2.4 inch center spacing) and 70 percent color contrast requirements. They mark hazards at curb cuts, rail platforms, and pedestrian crossings on parking-lot accessible routes.
Where Are Truncated Domes Required?
The most common parking-lot and sidewalk locations include:
- Curb ramps where the accessible route meets a vehicular way
- Hazardous vehicular areas without curbs that pedestrians must cross
- Rail and bus platform boarding edges
- Reflecting pools or other drop-offs adjacent to a walking surface
Per ADA Standards 705.3, placement and depth are coded. A typical curb-cut detectable warning runs 24 inches deep across the full width of the ramp, set within 8 inches of the curb edge.
What Are the ADA 705.1 Dimensions for a Truncated Dome?
ADA Standards 705.1 fixes the geometry of every dome on the panel. These are the numbers a specifier hands to the supplier:
| Spec | Requirement |
|---|---|
| Base diameter | 0.9 to 1.4 inches |
| Top diameter | 0.45 to 0.9 inches (50% to 65% of base) |
| Height | 0.2 inches |
| Center-to-center spacing | 1.6 to 2.4 inches |
| Base-to-base spacing | 0.65 inches minimum |
| Pattern | Aligned (square) grid |
How Does the 70 Percent Color Contrast Rule Work?
Under ADA Standards 705.2, the warning surface must contrast 70 percent or more with the adjacent walking surface. Contrast is measured in Light Reflectance Value (LRV), and the ratio runs:
(LRV_lighter - LRV_darker) / LRV_lighter x 100 >= 70%
In practice that pushes specifiers toward two color families: federal safety yellow (RAL 1023) on dark gray or dark concrete, or brick red on light tan or buff concrete. Both clear the 70 percent threshold against the most common adjacent walking surfaces. Custom colors are allowed but require an LRV calculation in the submittal.
What Are the Three Main Truncated Dome Product Types?
Cojo installs three system families, and the choice usually hinges on whether the curb is being poured today or was poured ten years ago.
Cast-in-Place Truncated Dome Panels
Cast-in-place panels are set into wet concrete during the pour. They sit flush, key into the slab with integral tabs or anchors, and become part of the curb ramp.
- Best for: new construction and full curb-ramp reconstruction
- Lifespan: 15 to 25 years
- Material families: composite, polymer concrete, vitrified ceramic
- Trade-off: cannot be installed on existing concrete
Surface-Applied Truncated Dome Panels
Surface-applied panels bond to existing cured concrete with a structural epoxy and mechanical anchors. The panel sits proud of the slab by roughly 0.2 to 0.3 inches.
- Best for: retrofits where ramp geometry is already correct
- Lifespan: 7 to 12 years
- Material families: composite, fiberglass-reinforced polymer, stainless steel
- Trade-off: edge lift is the dominant failure mode, so adhesive and anchor selection matter
Replaceable Cast-Iron Truncated Dome Panels
Replaceable cast-iron systems use a stainless or galvanized frame embedded at the pour, with a removable cast-iron plate that drops into the frame. When the plate wears, only the plate gets swapped.
- Best for: high-traffic transit platforms and freeze-thaw environments
- Lifespan: frame indefinite, plate 20 to 40 years
- Trade-off: highest first cost; only practical at scale
For a side-by-side spec walk-through, see our cast-in-place vs surface-applied truncated dome comparison.
What Does a Truncated Dome Installation Cost?
Installed costs in the Oregon I-5 corridor track these ranges.
Industry Baseline Range
| System | Per Square Foot Installed |
|---|---|
| Cast-in-place panels (new pour) | $25 to $60 |
| Surface-applied panels (retrofit) | $40 to $95 |
| Replaceable cast-iron plate system | $80 to $180 |
Current Market Reality
Through 2026, surface-applied retrofit pricing has run at the upper end of the baseline because of structural epoxy cost (ASTM C881 epoxies have moved with petrochemical pricing), traffic-control labor, and the fact that most retrofit jobs include curb-ramp slope correction the original installer skipped. For a per-curb-cut versus per-square-foot breakdown, see our truncated dome cost per square foot guide.
What Is a Real Cojo Install Reference?
In April 2026, Cojo retrofitted six curb cuts across a 38,000-square-foot Salem retail center where the original 2008 striping refresh skipped detectable warnings entirely. We installed surface-applied composite panels (federal yellow, 24 inches deep by ramp width) using ASTM C881 Type IV epoxy and stainless mechanical anchors. The panels passed a third-party LRV check at 71 percent against the surrounding broom-finished concrete. Total job ran nine working hours including traffic control on the access drive.
That kind of retrofit, where the ramps are already correctly sloped but missing detectable warnings, is the most common ADA-product job we run in the Willamette Valley. New-pour cast-in-place work shows up almost entirely on ground-up construction or full sidewalk replacement.
How Do You Specify a Truncated Dome Panel for a Project?
The specification, in the order it goes on the submittal:
- System type: cast-in-place, surface-applied, or replaceable
- Material: composite, polymer concrete, fiberglass, cast iron, or stainless
- Color and LRV calculation against adjacent surface
- Dimensions: 24-inch standard depth or platform-edge full-depth
- Pattern: aligned square grid per ADA 705.1
- Adhesive (surface-applied only): ASTM C881 Type IV epoxy, manufacturer-approved
- Anchors (surface-applied only): stainless steel, manufacturer-approved spacing
- Warranty: 5 years material, 1 year workmanship is the floor
For terminology questions when reading submittals, see our truncated dome vs detectable warning terminology explainer.
Truncated Domes in Oregon: Local Code Considerations
Oregon adopts the 2010 ADA Standards by reference, with state-specific accessibility provisions in OAR Chapter 918 Division 460. City code overlays add layers in Portland (Title 33), Salem (Chapter 79), and Eugene (Engineering Practices and Procedures). For city-level installation guidance, see truncated dome installation in Portland.
Get a Compliant Truncated Dome Install
Cojo installs ADA-compliant truncated dome panels for parking-lot accessible routes, sidewalk curb cuts, and transit-adjacent platforms across Oregon. We size the panels, calculate LRV against your existing surface, and document the install with as-built measurements that survive an audit.
Contact Cojo for a site-specific quote, or learn more about our striping services.