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Flat Roofs 101

A flat roof is a roof that has very low or no slope (slope is referred to as pitch in roofing terms), being defined as any roof with less than 10 degree pitch.

The American National Roofing Contractors Association defines a low-slope roof (or flat roof) as having 3-in-12 pitch or less, meaning that there is three feet or less of rise over a 12 foot span. Roofs termed ‘dead level’ have no intentional level toward the drains.

Flat Roofing Advantages

Flat roofs are associated with many advantages such as cost effectiveness and use of space. They are a very cost-effective roof shape because all of the space in a building can be used, whereas pitched roofs leave awkward spaces inside of a building.

They also enable to use of space on top if desired, which can have decking installed to make it suitable for foot traffic, or can be used for a solar panel installation or turned into a green roof in order to be more environmentally friendly.

Many people wonder about the cost of flat roofs compared with pitched roofs, but when done properly flat roofs are the cheaper of the two roofing options when considering the space that it grants.

A quality flat roof should last as long as pitched roof, but requires proper maintenance in order to do so. Flat roofing systems commonly range anywhere from 10 to 50 years, so when looking at re-roofing, make sure to find the product that will suit your building’s needs.

Expert Required

One of the important differences between flat and pitched roof installation is that most people are able to install or perform repairs on a pitched roof if inclined to do so, whereas a flat roof requires detailed and specific knowledge of products and processes in order to perform the desired function.

Flat roofing products rely of specific chemical formulas and certain products will simply not work together. Your flat roofer understands the product, their uses and limitations as well as the application process and anything that needs to be done in order to make the product last.

This knowledge and familiarity with products is very difficult for non-flat roofers to obtain, and we recommend using exclusively flat roofers. Since flat roofing products are so different from pitched roofing, your average pitched roofer will simply not have the knowledge required to install or fix a flat roof unless he has significant experience in this part of the industry.

Main Roofing Materials

There are two main schools of roofing, tar based and membrane based.

Tar based roofing is typically tar and gravel or modified bitumen (mod bit) and both rely on successive layers of felt and tar. This is an older style of roofing, usually involving a torch with open flame.

The tar, while not recyclable, is a by-product of petroleum refining and is similar to that used in roads. These roofs can last a long time if maintained properly but the tar tends to degrade rapidly when exposed to UV light and can therefore fail quickly if the gravel or granule-coated top coat is disturbed and not replaced.

Membrane roofing systems are newer systems that have been chemically designed to solve problems in older roofing systems. They are typically single-ply, and strips of membrane material are either solvent, glue or heat-welded together to form a continuous sheet.

The membrane from these roofs is often recyclable where facilities exist and many of them provide energy savings for your building. Leak detection is exceptionally easy on single-ply membrane roofs because there are so few seams to check as places of failure.

Leaks do not run underneath the product before entering the building, so the process of finding and repairing leaks is made simpler. If weight is a consideration, mechanically fastening these roofs can significantly reduce the weight they have to carry, enabling them to be appropriate foundations for both solar and green roof projects.

Maintenance Costs

It is good practice to have a yearly inspection of your flat roof performed by a professional in order to catch any problems arising from wind damage, water damage, seam and caulking delamination and/or foot traffic (if applicable).

You should also have an inspection done after any work on your roof from other contractors including HVAC and mechanical services. While they are experts in their field, these other contractors often have little or no knowledge of flat roofing products and procedures, often resulting in poor or non-existent waterproofing.

As your roof ages you will begin to have additional repairs. Your flat roof should last for about 20 years, so we recommend saving 1/20th the cost of a new roof each year so that by the time your roof needs replacing you will have the money saved up to do so.

As your roof approaches and passes the 20 year mark, you will want to take note of the yearly repair costs. If maintained properly, a roof is often able to last more than 20 years, and you don’t want to replace it prematurely.

We recommend that if you are still spending less on repairs and that 1/20th of a new roof cost, it is still appropriate to invest in the old roof. When the costs of repairs become larger than the yearly price of a roof, it is in your best interest to replace rather than repair.

The Importance of a Warranty

When replacing a roof you should always go with a flat roofing contractor who is willing to give a warranty on his work.

Three to five years is industry average, and a new roof should not have significant problems within this time. If a contractor is not willing to warranty their work, you should be asking yourself why not. If they are confident in their abilities there should be no problem in giving you that peace of mind.

Here at Northern Seal we offer a five year warranty on all new installs, with the option of extending that warranty to ten years through our roof maintenance plan.

Go with someone you can trust, call Northern Seal today for service on your flat roof!