Flat Roof Systems

Types Of Flat Roof Systems

Flat roof systems are roofs that are built so that they are nearly flat.  They are not completely flat; otherwise water would build up on the roof (called ponding) and would eventually start to get inside the building.  Flat roofs are built with a slight incline.  They are required to have at least a one-eighth-inch difference in height over each foot of the roof.   There are five main types of flat roof systems.

Roll Asphalt
A roll asphalt roof is made of material that is rolled onto the roof over roof felt and nailed down or applied with cold asphalt cement.  It is usually covered with a granular mineral surface, which looks like gravel.  The base material can be organic felt or fiberglass felt that is saturated in asphalt.  This is the cheapest building material, but it usually doesn’t last much beyond 10 years.

Single-ply
Single-ply flat roofs are composed of a single layer of a plastic or rubber-like compound.  Some of the more popular materials used today are thermoplastic polyolefin (TPO) and polyvinyl chloride (PVC), which are both very good at reflecting heat, which saves on cooling costs in the building.  Ethylene propylene diene monomer (EPDM) is also popular because it also cools well when white EPDM is used, and it is easy to install.  Rubberized asphalt is also used.  Single-ply roof systems, depending on the materials, can be self-adhered, applied with hot asphalt or installed by heating the back of the material with a torch.  Warranties for single-ply roofs usually are for 10 to 12 years.

Multiple-ply
Multiple-ply roof systems are also known as built-up roofs (BUR). These are made by overlapping rolls of felt or mats that are alternated with layers of asphalt.  This is covered by a granular mineral surface, ballast or tile to protect the layers.  These roofs can last 10 to 30 years.

Modified Bitumen
A modified bitumen roof is a multiple-ply roof that is made with modified bituminous membranes, which are made out of a blend of asphalt and a polymer.  This allows the asphalt to take on characteristics of the polymer, which is similar to materials used in single-ply roofs.  The modified bitumen roof is covered in a mineral or gravel surface, or a liquid coating that provides reflectivity.

Flat-seamed Metal
Flat-seamed metal roofs are made out of small sheets of metal that are soldered together.  The sheets are usually designed to look like tile or shingles.  The most common metals used for roofs today are copper, lead-coated copper or stainless steel. Metal roofs are light and reflect heat well, but are more expensive.

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3 Responses to “Flat Roof Systems”

  1. Matthew Matravers Says:

    I was wondering if anyone knows if edpm is really good and a long lasting product?

  2. Nevin Smith Says:

    Hi thanks for the info, very informative, do you have more info on pitched roofing systems? Thanks.

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