ASTM C957: Traffic Coatings for Parking Structures
Standard specification for liquid-applied elastomeric waterproofing membranes with integral wearing surface
Last updated: April 19, 2026
Overview
ASTM C957 is the standard that governs traffic coatings used on parking structures. If you manage a parking garage, this is the spec behind the coating system that keeps water from getting through the deck and into the concrete below. Unlike a bridge where the waterproofing membrane sits under an asphalt overlay, a parking structure traffic coating does double duty: it's the waterproofing AND the driving surface.
When the traffic coating fails, everything downstream fails with it. Water and dissolved road salts penetrate the concrete, reach the reinforcing steel, and start a corrosion cycle that leads to delamination, spalling, and eventually structural damage. A well-maintained traffic coating system is the single most important line of defense for a parking structure's service life.
Current edition is ASTM C957/C957M-17, reapproved in 2024 without technical changes. The companion guide, ASTM C1127, covers design and installation practices for C957 systems.
Scope
C957 covers cold liquid-applied elastomeric membranes for waterproofing building decks not subject to hydrostatic pressure. The membrane includes an integral wearing surface, meaning the coating IS the traffic surface. Covers single- or multi-component systems in one or more coats (base coat, intermediate, top coat).
What C957 does NOT cover:
- Specific requirements for skid resistance (project-specific)
- Fire retardance requirements (project-specific)
- Hot-applied membranes
- Sheet membrane systems
- Coatings under separate wearing surfaces (see ASTM C836 for those)
Performance Requirements
Key properties tested for C957 compliance:
| Property | Test Method | What It Measures |
|---|---|---|
| Tensile strength | ASTM D412 | Base coat: 900-1,200 psi typical. Top coat: 2,000-4,200 psi |
| Elongation at break | ASTM D412 | 130-800% (base coat 400-625% typical) |
| Weathering retention | ASTM D412 after G152/G154 | Tensile and elongation retention after UV exposure |
| Crack bridging | ASTM C1305 | Must bridge cracks at low temperature without failure |
| Adhesion (pull-off) | ASTM D4541 | 300-400 psi to primed concrete |
| Adhesion-in-peel | Per standard | To cement mortar and plywood substrates, tested after water immersion |
| Abrasion resistance | ASTM D4060 (Taber) | 25-30 mg loss per 1,000 cycles CS-17 wheel |
| Chemical resistance | Immersion testing | After water, ethylene glycol, and mineral spirits exposure |
| Recovery from elongation | Per standard | Return to original dimensions after stretch |
Note: The exact pass/fail thresholds are in the paid standard. The values above come from manufacturer product data for products that claim C957 compliance.
Referenced Test Methods
C957 references these ASTM test methods to define how each property is measured:
| Method | What It Measures |
|---|---|
| ASTM D412 | Tensile strength and elongation |
| ASTM D624 | Tear strength |
| ASTM D2240 | Shore hardness (durometer) |
| ASTM D4060 | Taber abrasion |
| ASTM D4541 | Pull-off adhesion |
| ASTM C1305 | Crack bridging ability |
| ASTM G152/G154 | Accelerated weathering (xenon arc/fluorescent UV) |
| ASTM D2697 | Volume solids content |
Coating Types
Four main chemistry types are used in parking structure traffic coatings. Each has different strengths, and the right choice depends on your project constraints.
Polyurethane (Most Common)
Elastomeric, good crack bridging, accommodates structural movement. Two-coat system is standard. Good for most parking applications. Service life 5-10 years in high-traffic areas, longer in low-traffic zones.
MMA/PMMA (Methyl Methacrylate)
Ultra-fast cure (60 minutes), trafficable in hours. Can be applied as low as -30 degrees C. Excellent durability. Strong odor is problematic in enclosed structures. More expensive than polyurethane systems.
PUMA (Polyurethane Methacrylate)
Hybrid of polyurethane flexibility and methacrylate speed. Rapid cure in 30-45 minutes. Can bridge moving cracks, unlike pure PMMA. Growing in popularity for fast-turnaround projects.
Epoxy Broadcast
Economical with a long track record. Fills pores and cracks well. But NOT elastomeric, so it cannot bridge moving cracks. Degrades under UV exposure (interior levels only). Not a C957 system on its own because it lacks crack bridging and elongation properties.
| Type | Cure Time | Elongation | Crack Bridging | UV Stable | Cost | Best For |
|---|---|---|---|---|---|---|
| Polyurethane | 24-48 hrs | 400-625% | Yes | Yes (aliphatic) | $$ | Most parking applications |
| MMA/PMMA | 60 min | 30-80% | Limited | Yes | $$$$ | Fast turnaround, cold weather |
| PUMA | 30-45 min | 100-300% | Yes | Yes | $$$ | Fast cure with flexibility |
| Epoxy broadcast | 12-24 hrs | 5-10% | No | No | $ | Interior levels only |
System Build-Up
A typical multi-coat polyurethane traffic coating system goes down in this sequence:
- Surface prep: shot blast to ICRI CSP 3-5
- Moisture test: ASTM F2170 (RH below 75-80%) or ASTM F1869 (MVER under 3 lbs)
- Primer: epoxy or polyurethane, applied to prepared concrete
- Base coat: 20-30 mils DFT (primary waterproofing layer)
- Aggregate broadcast: quartz sand or aluminum oxide for skid resistance
- Intermediate/wear coat: 15-20 mils DFT
- Top coat: 10-15 mils DFT (UV-stable aliphatic urethane for exposed decks)
Total system thickness ranges from 50-120 mils DFT depending on the product system and expected traffic loading.
Tip: On exposed top decks, always specify a UV-stable aliphatic urethane top coat. Aromatic urethanes yellow and chalk under sun exposure. On interior levels where UV isn't a factor, aromatic formulations save cost.
Surface Preparation
Shot blasting or scarification to ICRI CSP 3-5. The concrete profile must be open enough for the primer to penetrate but not so aggressive that you expose aggregate.
Moisture Testing
ASTM F2170 in-situ RH probes at 40% slab depth. Minimum 3 test holes per first 1,000 SF, 1 per additional 1,000 SF. Most manufacturers require RH below 75-80%. Alternatively, ASTM F1869 calcium chloride test with MVER under 3 lbs per 1,000 SF per 24 hours.
Substrate Requirements
- Clean, dry, sound concrete with no laitance, curing compounds, or contaminants
- Concrete minimum 14 days old and water-cured
- All cracks, joints, and penetrations addressed before coating
- Repairs and patches must be compatible with the coating system
Weather Requirements
Ambient temperature minimum 40-50 degrees F and rising. Substrate temperature at least 5 degrees F above dew point. No rain expected for 24-48 hours after application.
Warning: Moisture is the number one cause of traffic coating failure. Coating over wet concrete leads to blistering and delamination, often within the first year. Never skip the moisture test, even if the slab "looks dry."
Products & Manufacturers
Major traffic coating manufacturers by chemistry. Most are US-based:
| Manufacturer | Location | Product Line | Chemistry |
|---|---|---|---|
| Neogard (Hempel) | Dallas, TX | Auto-Gard (vehicular), Peda-Gard (pedestrian) | Polyurethane |
| Tremco CPG | Beachwood, OH | Vulkem 350/950NF/951NF | Polyurethane |
| Sika | Lyndhurst, NJ | Sikalastic DeckPro 710/715/720/735 | Polyurethane |
| Sika | Lyndhurst, NJ | Sikalastic TC 297 FS | PMMA |
| Pecora | Harleysville, PA | Pecora-Deck 800 series | Polyurethane |
| Polycoat | Santa Fe Springs, CA | Poly-I-Gard 125/246/575FC | Polyurethane/Polyurea hybrid |
| Stonhard (RPM) | Maple Shade, NJ | Stondeck FD2 Plus, FD4 | Polyurethane |
| Siplast (Soprema) | Irving, TX | Terapro | Polyurethane |
| APT | US | Qualideck | Polyurethane |
Tip: Most major traffic coating manufacturers are US-based. For BABA-covered projects (airport garages, transit parking), these products are well-positioned for compliance.
Maintenance & Recoating
Annual inspection is recommended, with semi-annual inspections for high-traffic structures. Look for wear-through, ponding water, loss of skid resistance, and any signs of coating delamination or blistering.
Recoat the wear course every 5-7 years in high-traffic areas. Full system lifespan is 15-25 years with proper maintenance. The decision between recoating and strip-and-replace comes down to the base membrane: if it's intact (verified with adhesion pull-off testing), recoat. If the base membrane is compromised or the system has been recoated multiple times, strip and start fresh.
Cost per Square Foot
| Treatment | Cost per SF |
|---|---|
| Penetrating sealers | $1-2 |
| Thin overlays | $5-7 |
| Full traffic membrane system | $7-10 |
The five-year rule: Have a specialist evaluate your traffic coating before the manufacturer's warranty expires. Catching problems at year 5 costs a fraction of a full replacement at year 10.
BABA Connection
Traffic coatings are polymer-based construction materials under BABA (Build America, Buy America). All manufacturing from initial combination of polymer inputs through final form must occur in the US. Most major manufacturers (Neogard in TX, Tremco in OH, Pecora in PA, Polycoat in CA, Stonhard in NJ) manufacture domestically.
BABA applies to airport garages (FAA), transit parking (FTA), and federal building garages. For privately funded parking structures, BABA does not apply.
For more on BABA requirements and how they apply to construction materials, see the Build America, Buy America deep reference and the Buy America Compliance Guide.
Frequently Asked Questions
What's the difference between C957 and C836?
C957 covers coatings where the membrane IS the wearing surface (you drive on it). C836 covers membranes that go under a separate wearing surface like pavers, topping slabs, or tile. If vehicles drive directly on the coating, you want C957.
How long does a traffic coating last?
The wear course typically needs recoating every 5-10 years in high-traffic areas. The full system (base membrane included) can last 15-25 years with proper maintenance and timely recoats.
Can I recoat over an existing traffic coating?
Yes, if the base membrane is intact and adhesion pull-off tests confirm good bond. No, if the base is delaminated, blistered, or otherwise compromised. When in doubt, cut test patches and pull.
Which coating type is best for my parking garage?
Polyurethane for most applications. MMA/PMMA if you need ultra-fast cure or are working in cold weather. Epoxy only for interior levels where UV isn't an issue and cracks aren't moving. PUMA when you need both speed and crack bridging.
Do I need to test moisture before applying?
Yes. ASTM F2170 (in-situ RH probes) or ASTM F1869 (calcium chloride). Moisture trapped below the coating causes blistering and delamination, often within the first year. This is the most common cause of premature failure.
Can traffic coatings be applied in cold weather?
Polyurethane systems require a minimum of 40-50 degrees F ambient temperature. MMA/PMMA systems can be applied as low as -30 degrees C, which is a major advantage for cold-climate garages that can't wait for spring.
How do I know when it's time to recoat?
Visible wear-through showing bare concrete, loss of color uniformity, ponding water that didn't pond before, and declining pull-off adhesion test results. Schedule an evaluation before the manufacturer's warranty expires.
Does BABA apply to traffic coatings on my parking garage?
Only if the garage is federally funded, such as airport garages (FAA), transit parking (FTA), or federal building garages. Most major traffic coating manufacturers are US-based, so compliance is typically straightforward.
This page is for informational purposes only and does not constitute engineering, procurement, or specification advice. ASTM standards are revised periodically. Consult the current edition of ASTM C957 and your project engineer for specification-level decisions.
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