Rosie on the House: The benefits of foam roofing

Question: What constitutes a flat roof?

Answer: Many homes in the southwest feature flat roofs, also known as “pueblo style.” The frame of a flat roof will typically incorporate some slope. A roof with a slope of less than 3 inches to 1 foot is considered flat. Water does need to run off this type of roof, so a minimum slope of one-quarter inch per foot will be built in. Many roofing materials are available that will waterproof a flat roof. One of them is foam roofing.

Q: What are the benefits of a foam roof?

A: Tim Forstie of Durafoam Roofing LLC, a Rosie on the House certified partner, says the primary reason to use foam is the insulation factor it provides.

For every inch of foam roofing, you will add an R-value of 6.5 to 7 to the insulation of your roof. Most foam roofs are done using at least 1 inch of foam. If you want a better insulation value, add additional thickness.

Foam is self-sealing. The product adheres to surfaces well, creating a tight water barrier for your home.

Foam roofs are also self-flashing, which means the top layer of the roof does not need fasteners, adhesives or rocks secured to the insulation or deck below. Roof penetrations such as pipes and ductwork don’t require specialized flashing systems. The foam seals around them.

Q: How is a foam roof installed?

A: As you may suspect, the foam installation process differs from shingle or tile roofing.

The foam is sprayed as a liquid in quarter-inch to one-half-inch passes as necessary to achieve the desired depth.

The foam rises and dries in about one minute.

If the roof is not constructed with a slope, then the foam can be applied in varying thicknesses to promote water drainage.

The surface that the foam is applied to, known as the substrate, can be any surface that is not blistering, peeling, rotting or otherwise damaged. Removal or repairs to that subsurface need to be made first.

If existing roofing needs to be torn off and the wood deck is in good condition, the foam can be applied directly to the wood decking. Underlayment is not required.

If the existing roofing is not damaged, the foam can be applied directly over it.

With new construction, foam is installed directly over the roof deck.

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Most homes with flat roofs will have a parapet wall around the perimeter. Often, cant strip is needed for fabric roofing to transition from a horizontal to a vertical surface. The cant strip is a piece of solid material that creates a 45-degree angle instead of a 90-degree angle and is not needed for foam roofing. Initially applied as a liquid, the 90-degree angle is not a problem and, unlike fabric roofing, this point on the roof is not a stress point for foam.

Forstie, of Durafoam Roofing, tells us that his crew often finds that stucco homes have stucco applied on top of the parapet wall. This stress point in the stucco is often cracked and causes leaks. Foam is applied directly over the crack after loose material is removed. This negates the need for costly stucco repairs.

Let’s get back to the slope. We all know that getting the water off the roof is the goal. When a flat roof does not have a slope built into it, Forstie tells us the foam can be applied in varying thicknesses to create one on most roofs. Starting in the middle or where the roof abuts a wall, applicators start with a 3- to 4-inch thickness and taper to 1 inch at the roof’s edge or at the scupper.

Where the thickness is insufficient, applicators will create a series of slopes and channels to facilitate water flow off the roof.

Q: How should I maintain and protect my home’s foam roof?

A: Like most materials, foam is susceptible to damage by UV rays of the sun. For protection, multiple layers of a UV-resistant coating are applied over the foam.

White is the most common coating color. White helps reflect the hot sun rays, adding to the positive effect of the insulation. Because some HOAs do not allow white, an off-white or beige color can be added to the coating mix.

As with all aspects of your house, there are some steps you need to take to protect your roof.

The most common is accumulation of debris from trees. Leaves falling on the roof can block scuppers, causing water to pond.

After a storm blows through, check your roof. Minor hailstorms are typically not a problem, but branches blown onto the roof can be a big one.

Forstie tells us that there are basically two types of roof warranties, a five-year and a 10-year. Both are based on time. The difference between them is the number of coats of protection applied. Each coat is about 10 to 15 millimeters thick.

A five-year warranty will have two layers of the protective coating, providing 20 to 30 millimeters of protection.

A 10-year warranty will have three layers of protection, providing 35 to 40 millimeters of protection.

The reason for the timing has to do with the fact that your roof will lose roughly one millimeter a year. When the roof coating gets below 10 millimeters, the UV rays begin to deteriorate the foam.

Foam roofing can be a great roofing material for new and re-roofs. With re-roofs, the foam can hide and protect against many flaws without extensive repairs before application.