Polyglass Underlayment

Why the Underlayment Brand Deserves Attention

On a tile roof this is the layer that keeps water out, and it is the layer that determines when you will next face significant roofing cost. The tile above it is the part you look at and the part manufacturers market.

So a proposal that names the tile manufacturer precisely and describes the underlayment as "synthetic underlayment" has specified the decorative layer and left the functional one vague. That is worth pushing back on.

High-Temperature Products

Roof-deck temperatures under tile in a Phoenix summer are severe, and this is the single most important underlayment property in this market.

Products carry temperature ratings, and a product rated for a milder climate ages faster here than its warranty term suggests. High-temperature formulations exist specifically for this application. Ask for the rating rather than assuming a premium product is automatically suited to desert conditions.

Self-Adhered Membranes

Self-adhered products bond to the deck rather than relying solely on fasteners, which seals around fastener penetrations rather than leaving them as pathways.

That matters at valleys, penetrations and roof-to-wall details, which is where the majority of tile roof leaks originate rather than in open field. Some specifications use a self-adhered product at those details with a different product across the field, which is a reasonable and economical approach.

Exposure Tolerance

During a tile lift-and-relay the underlayment sits exposed until tile goes back on, and projects run longer than planned for ordinary reasons: weather, sourcing, discovered deck damage.

Ask how long a product tolerates exposure. A product with a short exposure window on a project that stretches is a problem nobody planned for.

Where Underlayment Failures Actually Start

Not usually in the open field. They start at valleys, at roof-to-wall junctions, around penetrations and at transitions between roof areas, because those are where water concentrates and where the detail depends on installation rather than on the product alone.

Which means a premium underlayment across the field with ordinary detailing at the valleys is a poor allocation. Ask what product goes at the details, not just what goes on the roof.

What to Specify

• Product name and temperature rating
• Whether it is self-adhered, mechanically fastened, or a combination by roof area
• Exposure tolerance in days
• Number of layers and lap detail
• Whether the underlayment and tile warranties interact as a system

Our Relationship With This Manufacturer

Elite Roofing has confirmed it works with this manufacturer and installs their products in Arizona. Whether we hold a formal certification or authorized-installer credential with them, and at what tier, is [CLIENT: confirm certification tiers], and obtainable warranty tiers are [CLIENT: confirm product warranties].

We will tell you plainly whether we hold a certification with a manufacturer or simply install their products, because those are different things and the difference affects what warranty you can actually get. See warranties.