Metal Roofing vs. Rubber Roofing: Which Fits Your New England Home?

What is the difference between metal and rubber roofing?

The main difference is where each one belongs. Rubber roofing most often means EPDM, a synthetic rubber membrane laid in large sheets over flat or low-slope roofs, with seams bonded or taped. Metal roofing such as Interlock aluminum is made of interlocking panels that shed water down a pitched roof. A membrane is designed to hold back water that drains slowly across a nearly flat surface. Pitched-roof panels and shingles rely on gravity and overlap to move water off quickly. Neither works well in the other's job. There is also a second product sometimes called rubber roofing: shingles made largely from recycled rubber and plastics, shaped to look like slate or shake, for pitched roofs. That product competes more directly with aluminum, and it is covered later in this article.

Which parts of a New England home need rubber instead of metal?

Any roof section with a slope below 3/12 needs a membrane or another low-slope system instead of Interlock aluminum. The Interlock system requires at least a 3/12 slope, meaning 3 inches of rise for every 12 inches of run. In New England, that typically includes the flat or nearly flat roofs found on many triple-deckers in cities such as Worcester, Fall River, Providence and parts of Boston. It also includes many porch roofs, shed dormers on Capes, rear additions, breezeways and flat sections between gables on Victorians. A single house can easily have both. A Colonial might have a pitched main roof suited to aluminum Slate or Cedar Shingle and a low porch roof that needs a membrane. A good contractor measures each section's slope and recommends the right material for each, rather than forcing one product everywhere.

How do EPDM and metal handle New England weather?

EPDM and metal handle New England weather in different ways because they shed water differently. On a flat roof, an EPDM membrane must cope with standing water, snow sitting for weeks, and meltwater refreezing. Its weak points tend to be seams, flashings, penetrations and damage from foot traffic or shoveling. A pitched aluminum roof moves water off quickly and tends to shed snow, which needs snow guards over doors and walkways. Aluminum does not rust, so salt air on Cape Cod, the Islands, the North Shore and the Maine coast is not the same concern it is for steel. Neither material prevents ice dams. Ice dams form when heat escaping from the living space melts snow that refreezes at the eaves, so insulation, air sealing and ventilation address the cause. Ice damming is excluded from the material warranty.

How do recycled rubber shingles compare with aluminum?

Recycled rubber shingles and aluminum shingles both target pitched roofs and both can imitate slate or shake, but they are different materials with different strengths. Rubber shingles are molded from recycled rubber and plastics; aluminum shingles are formed metal panels with a coated finish. Products vary widely by manufacturer, so compare specific products rather than categories. Ask each supplier for the fire rating and the assembly it depends on, the impact and wind test results that apply, the warranty terms in writing, and the weight per square foot. For Interlock aluminum, panels weigh roughly 0.4 to 0.7 lb per square foot, the Alunar® finish has a 30 Year coating warranty, and the material and finish are covered by the Guardian Lifetime Limited Material Warranty for the original purchaser while they own the home, transferable once; workmanship is excluded.

Which should you choose?

Choose based on slope first, then on product details. If the section is below 3/12, a low-slope membrane such as EPDM is the right type of roof, and the question becomes which membrane system and installer to use. If the roof is pitched at 3/12 or more, compare aluminum with other pitched-roof options. For pitched roofs, think about how long you plan to stay, what look suits the house, coastal exposure, weight, and the written warranty terms. Interlock profiles include Slate, Cedar Shingle, Shake, Mediterranean Tile and Standing Seam, plus solid copper, in colors such as Black, Deep Charcoal, Hunter Green and Colonial Brown. For homes in a historic district, check with your local historic district commission before changing roofing materials. Condo owners in Massachusetts should check with their association or trustees under Chapter 183A.

Can metal and rubber roofing be used on the same house?

Yes, and on many New England homes it is the right answer. The pitched main roof gets aluminum shingles or standing seam, and the flat or low-slope sections get a membrane. The important part is the transition where the two meet. Flashing has to carry water from the pitched metal onto the membrane, or from a membrane up against a wall, without creating a spot where water collects or snow and ice hold moisture against a seam. These junctions are where many leaks start, so they deserve attention in the quote. If different contractors handle each part, agree in advance who is responsible for the transition. Mixed roofs are common on Capes, Colonials and older city homes, where porches, dormers and additions were built at different times. Ask to see how transitions are detailed during the consultation.

Common questions