Fiberglass shingles: what they are, what the code labels mean and what to put in writing

What a fiberglass shingle is made of

The National Roofing Contractors Association (NRCA) describes the product in three parts: a fiberglass mat in the middle, a layer of asphalt above and below it, and mineral granules pressed into the top. The granules are what you see from the ground. NRCA says asphalt shingles can be reinforced with organic or fiberglass materials, so "fiberglass shingle" names the reinforcement, not a separate material.

NRCA recommends shingles that comply with ASTM D3462, the specification for asphalt shingles made from glass felt and surfaced with mineral granules. It says not every shingle complies and that a compliant one is normally noted in the manufacturer's literature and on the package wrapper. That wrapper is worth keeping a photo of.

Three-tab, laminated and other forms

The Asphalt Roofing Manufacturers Association (ARMA) sorts steep-slope asphalt products into four groups. The first two are the ones most owners meet.

Source for the four forms: ARMA, Types of Asphalt Roofing (page dated May 2, 2017).

Two cautions from the same associations. NRCA says laminated grades give a textured look, which is a matter of appearance and not a code class. ARMA says most manufacturers do not recommend installing new shingles over existing laminated shingles, a point that matters when an owner asks about covering an old roof.

The labels the Virginia code asks for

Virginia adopted the 2021 International Residential Code as part of its building code. The roof chapter is read here on UpCodes, a third-party copy, because the code publisher's own site blocks automated reading; check the current official text with the county. Section R905.2 covers asphalt shingles, and the part that applies to a fiberglass shingle can be read as a chain of labels.

• Product standard. R905.2.4 says asphalt shingles comply with ASTM D3462.
• Wind label. R905.2.4.1 says shingles are tested to ASTM D7158 and the package bears a label naming that test and the class required for the site's ultimate design wind speed. Shingles outside D7158's scope may carry an ASTM D3161 label instead.
• Limit on the wind test. A footnote to the code's wind table says the D7158 calculations assume Exposure Category B or C and a building height of 60 feet or less; other conditions need additional calculations.
• Fire class. ARMA describes the roof-covering fire tests, ASTM E108 and UL 790, as giving Classes A, B and C, with A highest, and says they do not address fires starting inside the building.

The wind class a given site needs comes from the code's own table, which is set out on our roofing materials page; this page does not repeat it. Ask the county which design wind speed applies to your address.

Installation rules that sit around the shingle

A shingle's label means little without the parts under and around it. The same code section sets these, and they are what a written scope can name.

ARMA's nailing bulletin adds that an improperly adjusted pneumatic tool can cause sealing failures, raised tabs and blow-offs, and that nails belong below the sealant strip. Above a 21:12 slope the code hands installation entirely to the manufacturer's instructions.

ARMA bulletins on ventilation and application

ARMA publishes residential technical bulletins that read as plain-language companions to the code. Four are useful before signing anything.

Ventilation

ARMA ties attic ventilation to shingle buckling from deck movement, rot, moisture in insulation and ice dams. It describes intake at the eaves and exhaust at the ridge, split so that intake supplies 50 to 60 percent of the open area and exhaust 40 to 50 percent. It cites a long-standing ratio of 1 square foot of net free vent area per 150 square feet of attic floor, which codes generally allow to be reduced to 1 per 300 where features such as balanced ventilation and vapor retarders are present. The bulletin also warns that mixing different exhaust vent types above one attic can short-circuit airflow.

Underlayment

The underlayment bulletin lists felt types (ASTM D226 Type I and Type II, D4869) and self-adhering membranes (D1970). It says ventilation matters more when self-adhering underlayment covers the whole deck, because that layer behaves as a vapor retarder.

Replacement versus recover

The reroofing bulletin uses the code's terms: replacement removes the old covering and repairs the substrate; a recover adds a covering over the old one. It says local codes may limit the number of layers, that tear-off lets the deck be inspected, and that a reroof should include a check of attic ventilation. It also says impact ratings may be affected by a recover.

Drip edge and steep slopes

The residential index also lists bulletins on drip edge at eaves and rakes and on shingles above 21:12. These are the places a scope most often goes quiet, so ask whether the installer's instructions for them were read.

What Arlington records say

Arlington's historic nominations are the county's own written record of what is on older roofs. They name asphalt shingles but never a product. Two examples, both re-read from the Virginia Department of Historic Resources text:

Arlington Forest (2005). The nomination counts four roof forms, with the side gable on 85 percent of houses, and says every roof is clad in asphalt shingles except two in standing seam metal, at 117 North Galveston Street and 398 North Edison Street. It adds that the original shingles came in blends of red, green, purple and blue-black.

Glebewood Village (2004). The nomination describes many side-gabled houses with slate shingles and lists, among minor alterations, replacing slate with asphalt. It says those alterations have "very little impact on the integrity of the dwelling."

On permits, the county's residential page ties a re-roof to how much decking is replaced, not to the covering. The path for houses, townhouses, condos and historic districts is laid out on the Arlington roofing hub, and owners in shared buildings can read how decisions are made in the condo and co-op guide. Confirm your own case with the Permit Arlington Center.

A written scope for a shingle roof

Whoever does the work, these are the items a written scope can state in plain words. Each ties back to a source above.

• Tear-off or recover, stated plainly, with the number of existing layers and the shingle form (strip or laminated) now on the roof.
• Deck inspection and what happens to damaged boards or sheets; whether any decking is replaced, with the area, since that decides the county permit question.
• Underlayment type by its ASTM designation, double where the slope is between 2:12 and 4:12, and the extent of any ice barrier.
• The shingle's product standard (ASTM D3462), its wind test and class label, and its fire class listing, taken from the package or the manufacturer's literature.
• Nail type, length and count, and the instruction that the manufacturer's nailing pattern governs.
• Valley lining type, sidewall and chimney flashing, and drip edge at eaves and rakes.
• Attic ventilation: the existing intake and exhaust, whether they were checked and whether any change is proposed.
• Who pulls any permit, and for a condo or co-op who approves the work.

Our roof replacement and roof repair pages cover the wider process, the roofing insurance page covers claims paperwork, and our services list what Roofers of Arlington installs, repairs and replaces. This guide does not say we install any particular shingle product. To talk through your building, book a phone consultation or call (571) 397-6072; we will ask for the address, the building type and what you can see from the ground.