Flat Roof Construction Tips, showing a flat roof, Best Roofing Systems for Flat Roofs

Flat Roof Construction Tips

Update: August 5th 2019
Article Originally Published April 17, 2017

Flat Roof Construction Tips

Before you begin any roof construction project, there are a few factors to consider. This is especially true for commercial flat roofs. Flat roofs are susceptible to very specific kinds of wear and tear that need to be addressed. There are a wide variety of flat roof options on the market, all with different costs and benefits. Whether you are building a new commercial property or replacing an existing flat roof on your building, it is important to consider all of these factors before beginning construction. Here are some important tips to help you through the flat roof construction process.

Factors To Consider Before Selecting Your Roofing

Repair or Replace?:

Replacing an entire roofing system can be costly. If the majority of your roof is still in good condition, you may be able to save some money by having a professional repair the damage. You may also consider having your roof reconditioned. Depending on the extent of repair work necessary, however, it may be more cost effective to replace the roof. A trained professional will be able to help you weigh your options and make the best decision for you.

Roof Deck Integrity:

If you decide to replace your flat roof, you will need to have the structural integrity of your roof decking inspected first. If the structural integrity of the roof deck is damaged it will not hold up the roof. It’s advised to have your roof deck inspected by a professional before beginning any roof replacement.


Flat roofs have different challenges than low and high slope roofs. Flat roofs require a lot of thought about where rain, snow, and other precipitation will drain since they have no natural drainage system. As with any roofing system, if installed incorrectly flat roofs will leak. You need to make sure that the system you choose has both proper drainage and waterproofing materials like spray foam (SPF) or restoration coatings.

Load Weight:

If you plan on having a heavy load on your roof, such as a lounging area for employees, or heating and air conditioning units, you will need to select materials that will strengthen your roof and protect your structure from weight damage. SPF is one material to consider as it can withstand a great deal of weight.


Your roof needs to be designed to withstand the climate. If you live in an area with hot direct sun, you need a roof that can withstand heat and block against ultraviolet and ozone damage. If you live somewhere that gets very cold, you need a roofing material that has the ability to expand and contract with the temperature change.

Wind Uplift:

Another crucial environmental factor to consider is wind. Wind can be very damaging to any roof system so you need to be sure to choose a roofing material with wind resistance that meets the needs of your local area. A professional roofing company will be able to assess the average wind speeds in your area and help you choose a material that will withstand those speeds.


R-value is not a structure related concern, but it is an important consideration. The R-value is the reflective value of your roofing. Choosing a roofing material with a high R-value can save you a lot of money on energy bills, which is especially important on a larger commercial property. A low R-value material will allow heat to escape in the winter and to penetrate your building in the summer, resulting in higher energy bills to heat and cool your building. A higher R-value roof will require a bit more of an initial investment, but it will pay off in energy savings over time.

Selecting Your Roofing

You may want a particular roofing product for its appearance, such as a tile or shingle roof, however, this type of material should not be place on a flat roof as it will lead to building damage down the road. The following are some common flat roof options:

Built-Up Roofing (BUR):

Also called “tar and gravel roofing,” BUR roofing uses layers of roofing felts or ply sheets that are coated in asphalt or coal tar and topped with pea-size gravel. BUR roofs are the most common roofing style and very cost-effective. They do require some routine maintenance.

Modified Bitumen:

Modified Bitumen, also known as “torch-on” roofing, is very similar to BUR. Moreover, Modified Bitumen contains an additional polymer binder called Styrene Butadiene Styrene (SBS), which improves the durability and extends the lifespan of your roof.

Ethylene Propylene Diene Monomer (EPDM):

EPDM is a type of single-ply membrane roofing that uses a strong flexible polymer. It is resistant to the elements and is a great option for a roof in a harsh climate.

Thermoplastic Olefin (TPO):

TPO is another single-ply membrane that provides similar benefits to EPDM but does not offer as long of a lifespan.

Polyvinyl Chloride (PVC):

PVC is a single-ply membrane that provides similar benefits to EPDM and comes in a wide variety of colours and styles to match your architecture.

Each of these options varies in terms of costs and benefits, so it is important that you weigh them against the factors impacting your particular roof before making a final decision. The most important construction tip for a flat roof system is to consult an experienced professional in your local area.
Since 1952, Cambie Roofing has been constructing flat roof systems in the Vancouver area. We understand all the factors that can impact your construction and can help you identify which roofing system is best for your building. Call us today at 604.261.1111 or contact us on our website and let’s talk about how we can help your flat roof repair or replacement go smoothly.

2 Responses

Add a Comment

You must be logged in to post a comment