Aromatic vs. aliphatic
| Aromatic urethane | Aliphatic urethane | |
|---|---|---|
| Role | Base coat | Top coat |
| UV stability | Limited; chalks and yellows in sun | Good; holds color and gloss |
| Strength | High tensile and tear strength | Hard, abrasion-resistant surface |
| Cost | Lower | Higher |
A typical urethane system is an aromatic base coat for strength, topped with an aliphatic urethane, silicone or acrylic for UV protection. Moisture-cured polyurethane roof coatings are covered by the ASTM D6947 standard specification.
Where urethane earns its price
- Roofs with lots of foot traffic: HVAC-heavy restaurants and retail, medical and office buildings with frequent service calls
- Impact exposure: a harder, tougher film than silicone or acrylic. No coating is hail-proof, and we never promise one is
- Metal buildings: strong adhesion and toughness over seams and fasteners after a re-screw
- Base coat under silicone: some systems pair a urethane base for toughness with a silicone top for ponding and UV
- Spray foam: a protective coating over SPF where traffic is expected
Trade-offs to plan for
- Solvent-based products have more odor during application; we plan around air intakes and occupied spaces
- Usually two or more coats, so more labor than single-pass silicone
- Costs more per square foot than acrylic
Prep and process
- Moisture survey and photo report. We walk the roof, fly a drone for photos of areas that are hard to reach safely, and run drone thermal (infrared) scans that help show where water has gotten under the surface.
- Wet insulation and failed areas replaced
- Clean, prime as the manufacturer requires, and reinforce seams, penetrations and flashings
- Base coat, then top coat, each to the stated thickness, checked with a wet-mil gauge
- Walkway coatings or pads at equipment
Bidder checklist
- Base and top coat products named (aromatic, aliphatic, silicone or acrylic top)
- Thickness of each coat and total system thickness
- Odor control and scheduling around occupants and air intakes
- ASTM D6947 data sheet for the urethane
- Warranty type and term
Compare silicone and acrylic systems, or go back to commercial roof coatings.
Code sections and product standards are summarized in plain English from the published documents. Your building official and the manufacturer's current specification have the final word.
We're certified with GAF, CertainTeed, Owens Corning, Atlas, Johns Manville, Carlisle, Tropical Roofing Products, Mule-Hide and Enviroshake, and many other roof manufacturers.
Commercial warranty: a workmanship warranty from 10 years up to lifetime, depending on the job, plus both 10-year and 20-year NDL (no-dollar-limit) manufacturer warranties (the price depends on which NDL term you choose). Manufacturer coverage depends on the product and brand, and on the project qualifying for that manufacturer's program. We put the exact warranty for your roof in writing.
Certified, with 30 years installing every major roofing brand, a family roofing business going back 75 years, and over $80 million in completed roofing projects. 5.0 stars on Google at all three of our offices.
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