What Is Composite Roofing?

What composite roofing is

Composite roofing is a roof covering made in a factory by molding plastic or rubber into tiles. Most products copy the look of natural slate, which is split stone, or cedar shake, which is split wood. That is why people also call it synthetic slate or synthetic shake.

The material mix changes from brand to brand. One evaluation report we read describes tiles made from "virgin and recycled polyolefin polymers" ². Polyolefin is a family of plastics that includes polyethylene.

Another report describes tiles made with "a proprietary formulation of polymers and other additives" ¹. A proprietary formula is one the maker keeps secret. So two composite roofs can be made of quite different things.

The word "composite" also causes mix-ups. Some roofers say "composition shingles" when they mean ordinary asphalt shingles. That is a different product. This page is about molded polymer and rubber tiles, not asphalt shingles.

How a composite roof keeps water out

A composite roof works like a slate or shake roof. Each tile overlaps the one below it, so rain runs down from tile to tile and off the eave.

The part of each tile you can see is called the exposure. The rest is covered by the next row up. That overlap is what sheds water.

The tiles are not the only layer. Under them sits the underlayment, a sheet that catches any water that blows past the tiles.

One report we read calls for at least one layer of No. 30 felt over the whole deck, plus an ice barrier at the eaves in cold places ¹. Under the underlayment is the deck, the plywood or boards nailed to the rafters.

The same report calls for closely fitting solid sheathing, not spaced boards ¹.

Nails hold each tile to the deck. Reports name the nail size and type. One calls for two corrosion-resistant ring shank nails per tile, at least 1¾ inches long ¹. Another calls for stainless steel ring-shanked nails ².

A ring shank has ridges that grip the wood, so the nail is harder to pull out in wind. Metal flashing goes in the valleys and where the roof meets walls and chimneys, just as on other roofs.

The stack shows why the product report matters: it sets the nails, the underlayment and the deck, not just the tile.

Types of composite roofing

Composite products are sorted mostly by the look they copy and the base material. Profiles below are the ones named in the two reports we read ^{1 2}.

Some makers also sell rubber-based tiles. We did not load a report for one, so we make no claims about them here. The same rule applies: read that product's own report.

Evaluation reports: how a synthetic product proves it meets code

The building code has sections written for asphalt shingles, slate, clay tile, wood shakes and metal. It has no section named for polymer tiles. So makers get a third party to test the product and write an evaluation report. The report says how the product meets the code and on what terms.

Two groups publish most of these reports. ICC Evaluation Service, part of the group that writes the model codes, issues reports numbered ESR. UL issues reports numbered ER.

The UL report we read says it checked the product against ICC-ES Acceptance Criteria AC07 for special roofing systems ². Acceptance criteria are the test rules a product must pass to get a report.

Each report lists what it covered. The Brava report lists three things: weather resistance, fire classification and wind resistance ¹.

The EcoStar report lists uplift resistance, fire exposure, and the plastic tile tests in AC07, which include tension, bending and temperature cycling, both new and after artificial weathering ². Neither report lists impact resistance as an evaluated property.

That does not mean the products are weak in hail. It means hail ratings, if any, come from a different test.

Reports also expire. The Brava report says it was issued in November 2025 and is "subject to renewal November 2026" ¹. ICC-ES also says its reports are not an endorsement and carry no warranty ¹. Ask for the current report number and look it up yourself.

Worked example: reading two real evaluation reports

Here is what two reports we read actually say. This shows how much one product can differ from the next ^{1 2}.

The lesson: on a 3.5:12 roof, one of these products could go on at a short exposure and the other could not. Check your roof pitch against the report before you choose.

Where composite roofing is used

Composite tiles are most common on steep roofs where an owner wants the slate or shake look. Both reports we read set a lowest slope of 3:12 or 4:12, so these products are not for flat or low-slope roofs ^{1 2}. Low roofs need a membrane or low-slope system instead.

They also show up where real slate is too heavy for the framing. The Brava report gives an installed weight of about 304 to 310 pounds per 100 square feet ¹.

We did not load a source for the weight of natural slate, so we will not give one. Your roofer or an engineer can compare the two for your house.

Historic districts are another place people ask about synthetic slate. Whether it is allowed is up to the local review board, not the code. In wildfire areas, the fire class of the whole tested assembly matters most. The Brava report also comes with a California supplement for exterior wildfire exposure ¹.

Benefits of composite roofing

• The look without the stone. You get a slate or shake look from a molded product made to set widths ¹.
• Lighter than many heavy roofs. One report gives about 310 pounds per 100 square feet installed ¹. Ask your roofer how that compares with what your framing can carry.
• Fire class A is possible. Both reports list Class A when the tiles are installed in the tested assembly ^{1 2}.
• Wind tested. Reports cover wind uplift tests such as UL 580 ².
• Recycled content in some products. One report says the tiles use recycled polyolefin ².
• Clear install rules. The report spells out slope, deck, underlayment and nails, so you can hold the crew to it ¹.

Limitations of composite roofing

• Every product is different. You cannot judge "composite roofing" as a group. You have to read one product's report.
• Steep roofs only. The reports we read stop at 3:12 or 4:12 ^{1 2}.
• Class C is possible too. The same tile can be Class A in one assembly and Class C in another ¹. The underlayment and deck can make the difference.
• Impact class is not automatic. Neither report we read lists impact resistance as evaluated ^{1 2}.
• Insurance treatment varies. One insurer's hail discount guideline excludes synthetic polymer by name ⁸.
• Shorter track record. Natural slate and wood have centuries of use. Polymer tiles are much newer. Long-term claims come from makers.
• Fewer crews know it. Ask how many of these roofs the crew has put on.

What drives the cost of a composite roof

We do not quote prices. These are the things that move a composite roof quote. For numbers on your roof, use the roof cost calculator.

• The product line. Brands and profiles differ in material and thickness.
• Exposure. A shorter exposure means more tiles per roofing square.
• Underlayment the report calls for. Some assemblies need a specific underlayment to reach Class A.
• Deck work. Reports call for solid sheathing; spaced boards must be covered or replaced ¹.
• Tear-off. Removing the old roof adds labor and disposal.
• Roof shape. Valleys, hips, dormers and chimneys need cut tiles, accessory pieces and flashing.
• Accessory tiles. Starter, rake, valley, hip and ridge pieces are sold separately ¹.
• Crew experience. Fewer crews install these products, which can affect bids.

How a composite roof is installed

This is what you should see happen, drawn from the reports we read. It is not a do-it-yourself guide. Roof work is a fall risk, and a licensed roofer should do it.

1. The roofer gets the product's current evaluation report and the maker's install guide. The report says the guide must be on the job site ¹.
2. The crew checks the slope against the report's lowest slope for the exposure you picked ².
3. The old roof comes off, and damaged sheathing is replaced. The deck must be free of dirt and loose nails ¹.
4. An ice barrier goes along the eaves where the code calls for one, then underlayment over the whole deck ¹.
5. Starter tiles go on at the eave, then the first row on top of them ¹.
6. Each tile is fastened with the nails or screws the report names ¹.
7. Metal valley flashing and wall flashing go in, then hip and ridge pieces.
8. The building department inspects the roof if your area requires a permit.

Caring for a composite roof

• Keep a copy of the evaluation report number, the product name and the install date with your house papers.
• Have a roofer look at the roof after hail or high wind, and every few years.
• Keep valleys and gutters clear so water does not back up under the tiles.
• Trim branches that rub the roof.
• Do not pressure-wash the tiles unless the maker's care guide allows it.
• Ask the maker for spare tiles in your color, since colors change over the years.
• Do not walk the roof yourself. Leave it to a roofer with fall protection.

Warning signs and problems to watch

• Tiles that have slipped, lifted or cracked after a storm
• Nail heads showing where the next row should cover them
• Stains on the ceiling or in the attic under valleys or chimneys
• Gaps in flashing where the roof meets walls
• Color fading that differs from tile to tile
• A roofer who cannot name the evaluation report for the product they are installing

Code rules that apply to composite roofs

Composite tiles are approved through evaluation reports that point back to the code. Adoption varies by state and city, so your building department's edition applies.

Sources: [3] [4] [1] [2]

Fire and impact classes, side by side

These two ratings are often mixed up. They come from different tests and say different things.

Both impact tests use new, unweathered material. Professional Roofing notes that weathering lowers most roofing products' hail resistance ⁵. Our impact-resistant shingles page explains the tests in detail.

Composite roofing vs other roof coverings

Asphalt and metal slopes are from the 2021 IRC Chapter 9 ³. See metal roofing and how every roof covering compares.

Common misconceptions

Myth Composite roofing is the same as composition shingles.

Reality "Composition shingles" is an old name for asphalt shingles. Composite roofing here means molded polymer or rubber tiles.

Myth All synthetic slate is Class 4.

Reality Impact class is a separate test. The two reports we read do not list impact resistance as evaluated ^{1 2}. Ask for the UL 2218 or FM 4473 listing.

Myth All synthetic slate is Class A fire rated.

Reality Both reports list Class A or Class C, depending on the assembly ^{1 2}. The underlayment and deck matter.

Myth A synthetic roof always gets an insurance discount.

Reality Insurers set their own rules. One insurer's guideline we read leaves synthetic polymer out of its hail discount ⁸.

Myth Synthetic tiles can go on any roof.

Reality The reports we read set lowest slopes of 3:12 or 4:12 and call for solid sheathing ^{1 2}.

Local codes, climate and approvals

Your city or county adopts a code edition, and the evaluation report must cover that edition. The Brava report covers the 2021 and 2018 codes ¹. The EcoStar report we read covers 2018, 2015 and 2012 ². If your area is on a newer edition, ask whether the report has been updated.

Some reports carry state supplements. The Brava report includes a California supplement for wildfire exposure, a Florida supplement and a City of Los Angeles supplement ¹. Florida keeps its own product approval system, so ask for the Florida number there.

Cold climates need an ice barrier at the eaves; the report spells out the rule ¹. In hail country, ask for the impact listing and call your insurer before you sign. In historic districts, ask the review board first.

Is composite roofing right for you?

• Consider it if you want the slate or shake look on a steep roof and real slate is too heavy or too hard to find crews for.
• Get the current evaluation report number and check its slope, deck, underlayment, nails and fire class against your roof.
• If hail is a concern, ask for a separate UL 2218 or FM 4473 listing in writing.
• Call your insurer and ask, by product name, whether it earns any credit.
• Compare it with other coverings in the roof material selector.

Keep going

• Roofing materials guideHow composite compares with the other main coverings
• Roof replacementWhat a full reroof involves
• Storm damage and insuranceHow hail and wind claims work
• Roof pitch calculatorCheck your slope against the report's limits

Related terms

Synthetic Slate Roofing

Roofing tiles molded from polymers or rubber blends to look like natural slate at a fraction of its weight.

Slate Roofing

Slate roofing is a roof covering made of thin pieces of natural stone, split from quarried slate rock and nailed to a solid roof deck in overlapping rows.

Wood Shakes

Wood shakes are thick roof pieces split or sawn from logs, most often cedar, nailed in overlapping rows; wood shingles are their thinner, smoothly sawn cousins.

Impact-Resistant Shingles

Impact-resistant shingles are roof shingles that have passed a lab test in which steel balls or ice balls strike the shingle, and earned an impact class from 1 to 4, with Class 4 the highest.

Asphalt Shingles

Asphalt shingles are roofing pieces made from a fiberglass mat coated with asphalt and topped with mineral granules, laid in overlapping rows so water runs off the roof.

Metal Roofing

Metal roofing is a roof covering made of metal sheets, panels or shingles, most often steel, aluminum, copper or zinc, fastened to the roof deck to shed water, snow and sun.

Roof Underlayment

Roof underlayment is a sheet laid over the whole roof deck before the shingles or other roof covering go on.

Roof Pitch

Roof pitch is the steepness of a roof, written as the inches it rises for every 12 inches it runs horizontally, so a 6/12 roof climbs 6 inches per foot.

Also referenced from: Impact-Resistant Shingles