Mountain BIGFOOT 180 Synthetic Roofing Underlayment

Mountain’s BIGFOOT 180 synthetic underlayment delivers what Montana contractors actually need: 180-day UV exposure protection that handles Montana’s unpredictable weather windows. At 26 lbs per roll with 35x stronger tear resistance than 30lb felt, this underlayment transforms how crews approach roofing jobs. The 180-day UV rating matters when spring storms delay your shingle delivery or when homeowners can’t decide between architectural and designer shingles.

Skip it if you’re running a quick patch job or working with a homeowner who picked the cheapest bid. This underlayment targets contractors who understand that what goes under the shingles determines whether you’re back fixing ice dam damage in three years.

Extended UV Protection and Temperature Performance

The 180-day UV exposure rating changes the scheduling game entirely. Most synthetics give you 30-60 days before UV degradation kicks in. Mountain’s BIGFOOT gives you six months. That flexibility matters when you’re juggling multiple jobs through Montana’s construction season.

Temperature performance backs up the UV rating. The underlayment maintains integrity from -20°F to 221°F. That range covers everything from January deep freezes to August roof deck temperatures that’ll cook an egg. The 100% synthetic polyolefin/polypropylene construction won’t absorb moisture and buckle like felt when temperature swings hit.

Specification	Value	Source
UV Exposure Rating	180 days	manufacturer
Temperature Range	-20°F to 221°F	manufacturer
Material	100% inorganic synthetic polyolefin/polypropylene	manufacturer
Permeability (ASTM E96)	0.05	tested
Recyclable	100%	manufacturer

The synthetic material resists the freeze-thaw cycling that destroys felt in mountain climates. Maintains flexibility in cold weather; resistant to warping, wrinkling, and cracking.

Weight Efficiency and Coverage

Numbers tell the efficiency story. At 26 lbs per roll, BIGFOOT 180 weighs 8x less than traditional 30lb organic felt while delivering 1,000 square feet coverage. That’s fewer trips up the ladder, less strain on crews working at elevation, and more square feet per day covered.

The rolls pack efficiently too. 56 rolls per pallet means you can stage more material with the same footprint. Each roll provides 17% more coverage per course than standard 30lb felt rolls.

Coverage Metrics	BIGFOOT 180	Traditional 30lb Felt
Roll Weight	26 lbs	~200 lbs
Coverage	1,000 sq ft	~400 sq ft
Weight per Square	2.6 lbs	~20 lbs

Installation efficiency compounds the weight advantage. Cool Gray top layer reduces heat absorption, keeping the work surface cooler during summer installations. Less heat means less fatigue, especially on dark roof decks that turn into griddles by noon.

Strength and Durability Specifications

The 35x stronger tear resistance than 30lb felt translates to real jobsite durability. Wind won’t shred it. Boots won’t puncture it. Dropped bundles won’t compromise it.

Performance Metric	Test Method	Result
Tear Strength MD/CD	ASTM 4533	42 lbs / 38 lbs
Tensile Strength MD/CD	ASTM D751	108 lbs / 95 lbs
Burst Strength	ASTM D751	240 PSI
Elongation	ASTM D751	19%
Nominal Thickness	ASTM D1777	11 mil

These aren’t marketing numbers. 42 pounds of tear strength in the machine direction means crews can walk it, work on it, and weather-delay it without babying the material. The 240 PSI burst strength handles whatever Montana weather throws at it.

Safety Features for Mountain Work

BIGFOOT 180 tackles the slip hazard that makes roofers nervous. The Gripwalk gray surface on the top side provides legitimate traction for installers. Combined with the skid-resistant anti-slip coating on the underside, you get dual-surface grip that matters on steep pitches.

The underlayment meets OSHA compliance standards (29 CFR 1926.502). That’s not just paperwork—it means the material contributes to fall protection systems when properly installed. The Cool Gray top surface reduces glare compared to black underlayments, cutting eye strain during long summer days.

Installation follows standard practices with important details. Install parallel to eaves with the printed ‘Gripwalk’ side facing up. Horizontal laps: 4 inches; Vertical (end) laps: 6 inches. The critical difference: Must use corrosion-resistant plastic-cap or metal-cap nails with a minimum 1-inch diameter. Fasteners should be flush and 90 degrees to the deck.

Use of staples or fasteners without 1-inch caps will void the warranty. That’s not a suggestion—it’s a requirement that protects both the material integrity and your liability.

FAQ

How does 180-day UV exposure compare to standard synthetic underlayments? Common synthetic underlayments offer 30-60 day UV ratings. Mountain’s BIGFOOT 180 provides six months of UV protection, giving contractors flexibility for weather delays, material shortages, or scheduling conflicts common in Montana’s variable climate.

What roof slopes work with BIGFOOT 180? Recommended for roof pitches ≥ 4/12. Minimum slope is 2/12, which requires modified overlap of 50% + 1 inch. Not recommended for slopes less than 2/12.

What roofing materials can go over this underlayment? Compatible with mechanically attached asphalt shingles, metal roofing systems, and tile roofing (concrete/clay). Suitable for use under composition high quality asphalt shingles, tile, or metal roofs.

Does the 40-year warranty require specific installation methods? Using staples or fasteners without 1-inch caps voids the warranty. Corrosion-resistant plastic-cap or metal-cap nails with minimum 1-inch diameter must be used for warranty coverage.

How should valleys be prepared with this underlayment? Install a 36-inch wide self-adhered leak barrier in valleys first, then lap the underlayment 6 inches over the barrier. This creates a double-protection system for the most vulnerable roof areas.