Urethane sealants combine good adhesion to concrete and masonry with abrasion resistance and paintability, in one-part moisture-cure or two-part forms. Movement capability is typically plus or minus 25 to 50 percent. They weather faster than silicones, chalking and crazing on the surface after years of sun, and can bubble if applied over damp concrete or punctured rod.
Garage deck joints get the self-leveling urethane, the traffic coating bonds to it and won't touch silicone.
Urethane over damp concrete in the sun is the classic recipe for bubbles, so check the slab moisture before gunning.
Also heard as
- urethane
- PU sealant
Related terms
Silicone
A sealant with a silicon-oxygen backbone, prized for UV resistance and high movement capability.
STPE
Silyl-terminated polyether, a moisture-curing hybrid sealant that is paintable, weather-resistant and free of isocyanates.
Sealant
A material that fills a joint or gap to stop water and air, while accommodating movement.
Outgassing
Gas escaping into curing sealant or membrane from punctured rod or damp concrete, leaving bubbles and pinholes.