Flat Roofs

Flat roofs are everywhere – on hospitals, department stores, office buildings, even on some houses and garages. You might not noticed a flat roof, however, unless it’s on a house and it’s next to a sloped roof. But, what is a flat roof, exactly? Should you have one? Is a flat roof bad? How long do they last? Below we answer these questions and more.

We’ve installed and repaired flat roofs on everything from large commercial buildings to small home additions. If you need a new flat roof installed, an existing flat roof repaired, or an estimate, let us know. Estimates and inspections are free of charge.

What is a flat roof?

A flat roof is called ‘flat’ by comparison to its counterpart, the ‘pitched’ or ‘sloped’ roof. A flat roof appears flat compared to a sloped roof. However, a flat roof isn’t actually flat. It’s not perfectly level. What’s more, when looking at a commercial building with a flat roof from the street or alley, most often you’re looking at the parapet, which is the portion of an exterior wall that rises above the roof. Often you can’t see the flat roof from the street.

Who has a flat roof?

Although flat roofs are found most often on commercial buildings, such as hospitals, grocery stores, department stores, etc., you do occasionally see them on houses, apartment buildings, and home additions and garages. Flat roofs were popular on homes built in the 1940’s to the early 1970’s.

What are flat roofs called?

Flat roofs are often called just that – a flat roof. Other common names are ‘low-slope roof’, ‘commercial roof’, ‘single-ply roof’ or ‘single membrane roof’. To our residential customers, we refer to them as a flat roof. This is a general term, however. To general contractors and others in the business, we simply refer to the single-ply membrane that’s going to be installed onto the flat roof.

house with flat roof next to house with sloped roof
house with flat roof next to house with sloped roof

What are the components of a flat roof?

Here is a simplified diagram of a commercial flat roof and where it meets the wall (parapet).

a diagram of the components of a flat roof

How long do flat roofs last?

When properly installed, and depending upon the material used, weather, maintenance, etc., a flat roof should last between 15 and 30 years. Modified Bitumen has the shortest lifespan at 15 years. EPDM lasts the longest at 30 years. These are expected averages, mind you.

Are flat roofs bad?

It’s not a question whether a flat roof is bad or good. It often comes down to (a) whether you can have a flat roof, depending upon the pitch of your existing house or building (see Roofing Material Options for your Roof’s Pitch), or, if you’re building from scratch, (b) which style you want.

Modern Home

If you have an existing, relatively modern home with a pitched roof, you can’t install flat roofing materials onto that roof. It’s inappropriate and it won’t last. The same goes for installing sloped roofing material onto a flat roof. It won’t seal and hold water back, therefore it won’t last.

Older Home

Let’s say you have an older home with a flat roof. Consider yourself lucky because a flat roof often costs less to build and re-roof.

New Home

If you’re building a new home and you’re wondering if you should have a sloped roof or a flat one, consider your neighbors. Do they have flat or sloped roofs? Do you want to fit in or stand out? What’s the style of your new home? A flat roof is more appropriate if you’re going for that mid-century modern look or south western look. A pitched roof would fit right in if you’re designing your home to look more modern and traditional.

New Commercial Building

If you’re having a new commercial building built, what are you going to be doing in that building? PVC is the preferred choice if you’re going to be cooking or it’s a auto repair shop as it’s resistant to animal fats and grease. If you’re building a large department store, TPO, EPDM, or modified bitumen are your choices.

See flat roof advantages and disadvantages.