How To Find An Affordable and Reliable Underlayment for Metal Roof?

Metal roofing is notorious for being loud, cold and hot, loud when it rains, cold in the winter and hot when the sun shines. Metal roof materials can be thin or thick and have two common features, they are the best waterproofing solutions but are also the highest conductors of heat.

Metal roofing is also affordable, fast and easy to construct. As such, metal roofing is considered to be an extremely viable covering for homes, mobile homes and any form of the building.

The only way to provide added water and moist proofing as well as adding some thermal protection is by laying underlayment, usually a synthetic underlayment for metal roof applications.

Actually, the most important underlayment for a metal roof will be the thermal protection, since metal roofing does not provide any thermal protection at all. Metal conducts heat and cold perfectly and does not act as much of a barrier in extreme weather conditions.

Let’s take a look at the five best metal roof underlayment options on the market.

How to install synthetic underlayment for a metal roof.

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List of Top-Rated Underlayments for Metal Roof

PhotoProductThicknessCoverage/rollDetails
1. Tyvek Protec 160 Roof UnderlaymentTyvek Protec 160 Underlayment for Metal Roof14.9mils1000sq.ft.More Information
2. Grace Tri-Flex XTGrace Tri-Flex XT Underlayment for Metal Roof7mils1000sq.ft.More Information
3. Rhino roof underlaymentRhino Underlayment for Metal Roof7mils1000sq.ft.More Information
4. Titanium roof underlaymentTitanium Underlayment for Metal Roof45mils216sq.ft.More Information
5. Dupont Roof ProtectorDupont Protector & Underlayment for Metal Roof10mils1000sq.ft.More Information

The Best Underlayments for Metal Roof Reviews

1. Tyvek Protec 160 Underlayment for Metal Roof

Tyvek® Protec™ 160 roofing underlayment is a moisture protection product with great traction performance for roof applications.

Features

This product is formulated using an embossed pattern ingrained into the surface that provides safer traction when walking along the roof during application.

This is a lightweight material that is used to eliminate moisture issues under metal roofing.

Specifications

  • Nominal Thickness (mm) ASTM D1777 0.379 mm
  • Nominal Thickness (mils) ASTM D1777 14.9 mils
  • Fire rating ASTM E108 Class A
  • UV exposure ICC-ES AC188 180 days
  • Temperature range Thermal Cycling –40°F to 240°F (–40°C to 115°C)
  • Code approvals ICC-ES AC188, per Intertek CCRR-1062, ASTM D226
  • National Roofing Contractors Association
  • Western States Roofing Contractors Association Member
  • ASTM D226 Types I & II
  • ICC-ES AC188; Intertek approved (CCRR-1062)
  • Fire Rating Class A fire rating per ASTM E108

2. Grace Tri-Flex XT Underlayment for Metal Roof

TRI-FLEX® XT synthetic roofing is an underlayment material used to provide a waterproofing section between the metal roof and the ceiling underneath.

Features

TRI-FLEX® XT underlayment is made from a high strength woven synthetic material that is coated on both sides with slip-resistant polymers. This product is available in 10 sq rolls (48 in. wide x 250 ft long) and comes with two color options; black or gray topside surface.

This brand has a slip-resistant surface to secure a safer application. It is also a lighter material than standard #30 felt and covers by weight over 5 times the surface of feeling.

TRI-FLEX® XT is 20 times stronger than #30 felt and can withstand high winds that tear away nails.

Specifications

  • Weight 28 lbs (10 sq roll)
  • Thickness 7 mils ASTM D3767
  • Tear strength MD 58 lbs; CD 77 lbs ASTM D4533
  • Accelerated aging Pass (no damage, cracking, chipping) ICC-ES AC48
  • Ultraviolet resistance Pass (no peeling, chipping, cracking, flaking) ICC-ES AC48
  • Water ponding Pass (no percolation) ASTM D779
  • Pliability Pass (no cracks) ASTM D226
  • Water transmission Pass ASTM D4869
  • Tensile strength MD 96 lbs; CD 116 lbs ASTM D828

3. Rhino Underlayment for Metal Roof

RhinoRoof U20 is a coated woven synthetic roofing underlayment. This is a mechanically attached material for roofing.

Features

RhinoRoof U20 is fabricated with a fiber grip walking surface that provides a safe surface for walking over when applying and can be chalked upon just as felt.

This is air, water and vapor barrier underlayment for metal roof’s and is best applied over all surfaces included ventilated locations. This product can be left exposed during installation for up to 60 days before requiring replacement.

Specifications

  • Meets ASTM D4869 & D226 Types I & II
  • Fiber grip slip-resistant walking surface
  • Enhanced UV – 60 days exposure
  • Inert to mold growth
  • Lays flat and does not absorb water and wrinkle
  • No oil leaching
  • No hazardous material content
  • Class A Fire – ASTM E108 (as part of a system)
  • Contributes to LEED® points
  • Advanced backside non-slip coating
  • Low-temperature flexibility

4. Titanium Underlayment for Metal Roof

Interwrap Titanium® PSU30 is a thick professional self-adhesive synthetic roofing underlayment. This product is 45 mils thick, so it’s perfect for protecting under your metal roof from wind-driven rain, water, snow and even from ice dams.

Features

Titanium® PSU30 is a patented rubberized asphalt Peel and Stick underlayment that has been modified and includes the proprietary using Sure-Foot® nodular walking surface technology.

This means you can use this product safely on the steepest of roof applications with a high level of safety confidence.

PSU30 is used on 2:12 or greater angled roofs and provides full waterproofing protection. This product provides a rubberized asphalt adhesive that delivers high temperature (240°F / 115°C) flow resistance, and low temperature (40°F / 4.4°C) deck adhesion.

Features

  • Watertight asphalt to asphalt lap system
  • Up to 6 months UV exposure rating
  • Meets and exceeds ASTM D1970
  • ICC ES Approved
  • Class A Fire ASTM E108, CAN/CSA A220.1
  • Meets Class 4 Hail Rating

5. Dupont Protector & Underlayment for Metal Roof

DuPont™ Roof Protector™ is waterproofing underlayment that has a high strength to weight ratio. This is an excellent lightweight and durable water barrier for placing under metal roofs.

Features

DuPont™ Roof Protector™ has a slip-resistant surface that is much less prone to wind pull-up and fastner point tearing. It is designed to apply to steep slopes under metal panel roof materials.

The construction of this brand is exceptional, with a four-layer configuration that delivers a strong, gripping water-resistant and slip-resistant surface with chalks mark guidelines.

Specifications

  • 90-day UV resistance
  • Class “A” fire rating per ASTM E108
  • Meets AC188 (Intertek CCRR-1062), ASTM D226 Types 1 & II, CAN/CSA A123.3, CAN/CSA A220.1
  • Length per roll 286 ft
  • Width per roll 42 in
  • Weight per roll 20 lb
  • Roll size 42″x286′ (10 square)
  • Rolls per pallet 49
  • Pallet weight 1,095 LB
  • Weight per square 2.04 LB

Is underlayment necessary for a metal roof?

As a rule of thumb, no. Metal roofing can stand alone; However, if you want a cool and water free environment for a very long time, then underlayment is a must.

Metal roofing is notoriously hot in the summer, cold in the winter, and in high winds, if not affixed properly, will rip off the roof. As such, an underlayment will provide added protection to your home that includes insulation as well as waterproofing and moisture elimination.

What is roof underlayment?

Underlay or underlayment can be any number of layers that come between the metal roof and the ceiling of the house. These include waterproofing, reflective surfaces for insulation, and thermal insulation.

Underlayment materials are application focused, and they come in a wide variety of materials and configurations.

What kind of underlayment for a metal roof?

Any underlayment that works for tile roofing is good for metal roofing and vice versa. However, to be more precise and detailed that are many different types of roof underlayment for metal roof sheets and these are based on location.

Since metal roofing is not thermally protective, you need to consider buying insulation materials as well as moisture and waterproofing underlayment for under a metal roof.

Another feature that metal roof underlayment must have that is not necessary for tile roof application has a smooth non-granulated surface. You don’t want the tougher underlayment materials to scratch the backs of the metal roof panels.

There are usually three layers of underlayment to a metal roof project, and these include the ice and water shield. These underlayment materials are usually rubberized-asphalt or butyl-based adhesive with a polyethylene carrier sheet.

This layer has to be able to withstand the hot surface temperature of the roof on a sunny day.

The second layer should be a polypropylene scrim reinforced underlayment that is constructed out of multiple layers. This serves as a moisture barrier, and also as a slip sheet.

However, this is good for cold locations, if you live in a hot climate than you want to add to this the third layer of reflective or breathing insulation that will protect the house from heat buildup, and this leads us to the third layer that is a recent addition to the underlayment.

How to install synthetic roof underlayment

1. Install the Drip Edge

Your first step is to apply a drip edge to the eave and cut drip edge flashings at the corners, pressing them lightly on the eave end. Now lightly hammer in a nail at the end, and always align the material using the chalk line.

2. Overlap and Cut Drip Edges
Make sure you overlap meeting drip edges by 2 inches and when they meet in a valet, cut the overlapping tabs and press these tabs firmly to form a seamless, clean corner.

3. Align the Felt
Roll out around 12 feet of material using the chalk line as a guide. Make sure there are no creases or bubbles and reroll and unroll to make sure of this. While unrolling, peel off the paper backing.

Try adhering the bottom half first on steeply angled roofs. You can also apply the underlayment at the same time as the felt during dry spells. After this install the shingles. Add more felt when you are 6 inches away from the top edge.

Valley Application

You must always apply for extra protection at the valley. You do this by rolling out the material and driving nails on one side to temporarily hold it in place.

Now fold over the other side while peeling off the paper backing and press into place. After this remove the nails and peel off the paper from the other side.

Maintaining Parallelism

When overlapping, add at least 4 inches and use the chalk line as a guide. Using the lines as guides will assure that all applications are parallel and reduce bubbling, creasing and basically ugly roofing work.

Apply the Underlayment

Make sure to apply the underlayment up to but no more than 4 inches from the ridge and overlap the felt on the ridge with at least 8 inches on either side.

Roof to Wall Completion

Lap the underlayment to the wall where it meets the roof by 4 inches. You might need to detach and reattach sidings to do this.

Conclusions

Metal roof underlayment is a must have for residential and commercial purposes. While they are perfect waterproofing solutions, they are terrible insulators and require underlayment that will add a layer of insulation as well as protect from moisture build-up and in some instances act as an additional water protector.

About the author

Jessica Nickson

Jessica Nickson

Jessica Nickson is a keen home and garden innovator with over 25 years of hands-on experience in, home improvement, landscape gardening and all things appliance related to making life easier and more interesting. You can contact her via e-mail - jessica@thehomedweller.com.

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