Polystick MTS Plus Review: High-Temperature Underlayment for Metal Roofs

For many of our metal roofing projects from Palm Beach County north through Martin and St. Lucie, Polystick MTS Plus is an underlayment we are comfortable recommending. We like its high-temperature capability and self-adhered water protection, and it generally costs us less in material than Polystick XFR.

That is our purchasing and installation preference, not a claim that MTS Plus is better in every situation. If the approved roof needs an XFR-based fire-rated assembly, the lower material price is not a reason to substitute MTS Plus.

Product capabilities: Polyglass MTS Plus product page. Cost preference: M&M’s experience; no fixed price or savings percentage is implied.

MTS Plus uses Polyglass’s ADESO dual-compound construction: a modified-bitumen upper layer and an adhesive SBS underside protected by split release film. Its cavitated top film is designed for traction; roof fall protection is still essential. Manufacturer overview.

Sizes and coverage are nominal/approximate. Lab properties are not a whole-roof wind rating or a guarantee against leaks. Read the complete product data sheet.

We primarily use MTS Plus beneath compatible metal roofing in these counties and other suitable locations farther north. The practical question is whether this underlayment works with the specified deck, metal panels, fire classification and permit documents.

Broward and Miami-Dade are Florida’s High-Velocity Hurricane Zone (HVHZ). Our typical choice there is an appropriate Polystick XFR assembly. Outside the HVHZ, approvals and fire requirements still apply; crossing the Palm Beach County line does not automatically make any roof assembly acceptable.

For the covering above it, see our 1.5-inch mechanically seamed metal roof review, including how concealed clips attach the panels.

Class A describes a tested roof assembly—not an underlayment roll in isolation. Do not assume MTS Plus alone beneath metal over a wood deck provides Class A performance. A “UL Classified” mark by itself is not enough to make that conclusion.

Miami-Dade’s published guidance ties fire-class requirements to the building’s conditions and requires fire-directory listings for metal systems. It does not say that every metal roof in both counties must use XFR. Read the county’s fire-classification guidance.

We select XFR when its listed assembly meets the project’s needs. Even XFR is not a universal one-layer answer: Polyglass’s published Class A configurations differ for steel/copper and aluminum. The exact deck, panel material, layers and current fire listing must match. Polyglass fire-assembly reference.

Underlayment acceptance and compatibility: NOA 25-0121.12, pages 18 and 21. Final permit acceptance rests with the building authority.

VS

Polystick

MTS Plus

Our cost-efficient waterproofing option

Secondary water barrier with approved direct-to-deck installation

Polystick

XFR

Fire-resistant underlayment

Lower material cost, with secondary water protection. For compatible metal-roof systems, MTS Plus generally costs us less in material than XFR, based on M&M’s purchasing experience. It can still serve as a secondary water barrier when installed directly to the structural deck as permitted by the approved assembly. Any insurance discount depends on the documented installation, inspection and insurer approval. Manufacturer SWR bulletin.

Product comparison: 2026 Polyglass brochure. Fire configurations: XFR assembly reference. Insurance details are explained below.

Price each option by the installed square footage and required number of layers. Waste, deck preparation and additional components also matter. A less expensive roll is not necessarily a less expensive approved system.

It may—but the credit is not automatic. Polyglass specifically includes MTS Plus in its SWR bulletin for installation directly to the structural roof deck where code permits. This is the documented installation route we discuss when a homeowner wants a secondary water barrier. Manufacturer SWR bulletin.

An approved installation over a base sheet is a different assembly. Do not assume it has the same insurance treatment; have the inspector and carrier evaluate the actual roof. Equally, do not assume that every peel-and-stick material earns a discount simply because it is self-adhered.

The current Florida wind-mitigation form, Rev. 04/26, records several SWR methods and warns that some listed items may not qualify for discounts. The inspector documents the condition; the insurer determines the applicable credit. No savings amount is guaranteed.

We could not confirm a product-specific cooling or energy-savings benefit from MTS Plus’s color in the current manufacturer literature reviewed. Its published temperature limit tells us about heat tolerance; it is not a solar-reflectance value, insulation rating or predicted reduction in your electric bill.

We recommend MTS Plus for its underlayment role, not a cooling promise. If thermal performance is a priority, evaluate the exposed metal panel finish and the complete roof/attic design separately. Current technical data.

Our review is a homeowner’s guide, not a substitute for the installation instructions or an engineered attachment schedule. The actual metal roof approval must accept the proposed underlayment arrangement.

1. Deck and moisture conditions. Confirm a sound, suitable substrate and address ventilation or vapor-control concerns before choosing direct adhesion versus a base sheet.
2. Preparation and bond. Use a clean, dry, smooth surface, maintain the specified laps and apply firm pressure. Do not treat it as a recover sheet over old roofing.
3. Attachment and transitions. Follow the selected approval for covered backnailing, eaves, valleys, walls and penetrations. Self-adhered does not mean fastener-free.
4. Covering compatibility. Check the panel manufacturer’s requirements and warranty terms before installation. Underlayment approval alone does not approve the finished roof.

See the manufacturer instructions and complete NOA. As one specific example—not a universal specification—NOA system F(1) lists MTS Plus directly over 19/32-inch plywood or wood plank with specified capped backnailing. Do not transfer that detail to a different deck or assembly.

For related reading, explore mechanical seam vs. nailstrip roofing or our XFR review.

These are official manufacturer, government and insurer sources checked for this review. An approval is conditional—not an endorsement or permission to substitute components. Recheck current status and revisions for the permit date.

Florida Product Approval FL5259-R50 separates HVHZ and non-HVHZ applications. Its non-HVHZ substrate table includes OSB and Huber ZIP panels for MTS Plus; the HVHZ table lists plywood and Southern Yellow Pine but not OSB. Do not interchange the substrate or attachment details. Non-HVHZ report · HVHZ report.

There is no single wind-pressure number in this review: the approval covers multiple systems, and its highest listed pressure must not be presented as a generic MTS Plus metal-roof rating. Both evaluations also exclude fire classification.

• Polyglass MTS Plus product page

  Product overview and original manufacturer product image.

• MTS Plus product data sheet — July 2025

  Roll dimensions, ASTM properties and application instructions; pages 1–2.

• Polyglass 2026 Polystick brochure

  MTS Plus and XFR features, system roles and comparison table; pages 4–7.

• Miami-Dade County, Florida NOA 25-0121.12 — expires September 13, 2027

  Approved March 20, 2025. Direct-deck F(1): page 15. Fire exclusion: page 18. Covering compatibility: page 21. Read the complete NOA.

• Florida Product Approval FL5259-R50

  Approved February 10, 2026, for the 2023 FBC. FL5259.1: HVHZ; FL5259.2: non-HVHZ. The application covers multiple products and systems.

• FL5259-R50 non-HVHZ evaluation / installation report

  PEER-PLYG-002.A.R47, revised December 11, 2025. Substrate table and non-tile direct-deck provisions; read the complete report.

• FL5259-R50 HVHZ evaluation / installation report

  PEER-PLYG-002.B.R19, revised December 11, 2025. HVHZ substrates, backnailing and limitations; read the complete report.

• Miami-Dade 2023 Florida Building Code roofing guidance

  Fire-classification requirements and listed roof systems; page 34.

• Polyglass XFR fire-assembly brochure

  Assembly-dependent Class A configurations; verify the current UL TGFU.R25992 listing for each project.

• Polyglass SWR Technical Bulletin 2010-01

  Revised July 17, 2025; identifies MTS Plus and direct-to-structural-deck installation, subject to acceptance.

• Florida OIR-B1-1802 wind-mitigation form — Rev. 04/26

  Section 8 documents secondary water resistance; the form warns that some listed items may not qualify for discounts.

• Citizens Wind Loss Mitigation Guide — Rev. 04/26

  SWR documentation and sealed-roof-deck classification; page 15.