GAF ArmorShield II Roof Replacement on Moonlight Drive in Longmont, CO - Ice Damming and Undersized Ventilation

The Problem

Bruce and Judy bought their home on Moonlight Drive in Longmont, CO in 2024, and the roof was still the original one from when the house was built back in 2005, already twenty years old. That first winter in the house, Bruce noticed water making its way into the soffits on the north side above the front porch. Their insurance agent pointed them toward WestPro, and our inspection confirmed exactly what they were starting to suspect: ice damming.

Why It Needed Replacing

Ice damming happens when heat escapes into the attic during winter, melts the snow sitting on the roof above, and that melt-water refreezes once it reaches the colder eaves. From there it backs up under the shingles and works its way inside, which is exactly what was happening on the north side over the porch. Combine that with a twenty-year-old roof and ventilation that wasn't doing its job, and there was no reasonable repair path forward. The whole roof needed to come off.

What We Did

The attic inspection turned up the real culprit: the ventilation system was undersized for a Colorado winter, and that shortfall was feeding the ice damming directly. GAF actually requires adequate ventilation to keep its shingle warranty valid, so correcting the ventilation wasn't optional, it was part of doing the job right.

We performed a full tear-off, and the plywood sheathing underneath turned out to be in solid shape, no resheathing needed. The crew installed two courses of GAF WeatherWatch Leak Barrier along the eaves to meet Longmont's code requirement, then added three additional rolls beyond the standard order at no extra charge to give the large porch soffit area the kind of protection that would prevent a repeat of the original leak. For shingles, Bruce and Judy chose GAF ArmorShield II in Weathered Wood, a Class 4 impact-resistant product. To fix the ventilation shortfall, we installed 12 slant-back vents along with 42 linear feet of GAF Cobra IntakePro intake venting, finally giving the attic a properly balanced system instead of the undersized one it started with.

Project Details

This project covered a full roof replacement on a single-family home in Longmont, CO, built in 2005. Scope included a full tear-off of one existing shingle layer, code-required leak barrier along the eaves with extra material added over the porch soffit, and a ventilation overhaul with new slant-back and intake venting. The project was completed December 19, 2025.

Materials Used​

• GAF ArmorShield II Shingles in Weathered Wood (Class 4 impact-resistant)
  
• GAF WeatherWatch Leak Barrier (eaves, two courses plus extra rolls over porch soffit)
  
• GAF FeltBuster underlayment
  
• 12 slant-back vents
  
• GAF Cobra IntakePro intake venting (42 linear feet, eaves)
  

The Result

Bruce and Judy were very happy with how the project turned out. The leak that started the whole conversation is solved at the source, both the ice damming risk and the ventilation problem that was causing it, and the new roof carries a full GAF System Plus warranty backed by ventilation that actually meets the manufacturer's requirements. Stories like this aren't unusual in Longmont, where a home's original roof and its original ventilation often reach the end of their useful life around the same time, especially once winter ice starts finding the weak points.

Price Context

GAF ArmorShield II, a Class 4 impact-resistant shingle, typically runs $6.75 to $8.50 per sq. ft. installed for most homeowners, based on an average 2,500 sq. ft. roof area at a 4:12 pitch with a single-layer tear-off. Ventilation upgrades and extra leak barrier material, like the additional protection added over this home's porch soffit, can add to the total depending on scope. Curious what a project like this would run for your home? Run your address through our free roof cost calculator for a starting estimate, then schedule a full inspection for exact pricing.