Polyurethane roof coatings are popular for their durability and waterproofing qualities, often used to extend the life of a roof and improve its resistance to weather and UV damage. When it comes to underlayment, the choice depends on your roof type and climate. Polyurethane coatings work best over smooth, clean, and fully cured substrates, such as properly applied asphalt or modified bitumen membranes, or single-ply membranes like TPO or EPDM. The underlayment’s main role is to provide a stable, dry, and compatible surface that won’t react poorly with the polyurethane. Problems like bubbling or peeling often happen if moisture is trapped beneath the coating or if the underlayment is not fully cured or clean. Homeowners can perform simple visual inspections for blistering, cracks, or discoloration on the underlayment before applying the coating, and gently test for moisture by feeling if the roof feels damp or by using a moisture meter. Avoid walking on the roof excessively during inspection to prevent damage.
If you’re uncertain about the condition of your existing roof or underlayment, it’s wise to call a professional roofer who specializes in polyurethane applications. They can assess if the current underlayer is compatible or recommend replacing it with a solvent-resistant and fully cured product. When discussing options with a contractor, ask whether the polyurethane coating they use is compatible with your exact underlayment type, and how they test the roof surface for moisture before application. Confirm if their warranty covers issues arising from underlayment failure or improper surface preparation, so you know you’re protected in the long term. This approach ensures your coating will bond correctly and last, avoiding costly repairs down the road.