Say you’re a building owner and you want to install a brand-new roofing system. Which kind of roofing system should you choose?
Probably a roofing system that costs the least…correct?
Today we’re going to compare the two most popular commercial roofing systems out there, single-ply and spray polyurethane foam.
In this article, we’ll talk about:
- The initial costs of each system
- The life-time costs of each system
- Why each one costs what it costs
- Other drivers of cost that you didn’t consider
Since 1979, West Roofing Systems has been installing spray foam roofs. And we constantly battle against single-ply roofing companies who say single-ply is cheaper than spray foam.
Single-ply is cheaper than spray foam in some situations.
However, single-ply costs about the same in some situations. And single-ply is more expensive in other calculations, such as life-time cost.
Let’s get into the reasons one roofing system will cost more, equal, or less than the other…
A quick introduction to single-ply roofing systems
A single-ply roofing system is a roof that’s installed using large sheets of rubber, plastic, or other combined compounds. They are installed over insulation and are fastened to that insulation in one of three ways:
- Using plates and screws
- Using an adhesive
- Or ballasted, meaning using rocks or stones to hold the sheets down.
A quick introduction to spray foam roofing systems
A spray foam roofing system is a roof that’s installed using a 1-1 ratio of two chemicals (an isocyanate and a resin). After the foam is sprayed down, a thin layer of coating (usually silicone) is installed over top. Then a layer of granules is embedded into that coating to provide stability and strength.
Here’s a video of a spray foam roof installation from start to finish:
What are the initial costs of single-ply and spray foam roofing?
The average single-ply roofing system can be installed for $6 – $12 per square foot.
The average spray foam roofing system can be installed for $6 – $12 per square foot.
There are a ton of variables that increase/decrease the price, including:
Location of the roofing contractor
If a single-ply roofer is 2 miles away and the spray foam roofer is 150 miles away, single-ply has an advantage.
The amount of tear-off
If you have water trapped in your insulation, this needs to be removed before doing any roofing project. The more saturated your insulation is, the more expensive each system is going to be.
When is a single-ply roof cheaper?
A single-ply roof can be cheaper than spray foam when there’s no minimum R-value to achieve. If you aren’t removing the existing roof, then there isn’t a minimum R-value you need to hit to stay compliant with building codes.
For Ohio, a minimum of an R-25 is needed for all new roofs and for roofs that are being torn off and replaced.
A single-ply system can be installed over an existing roof. It can be installed with the cheapest insulation board, the minimum amount of materials possible, then lay down the single-ply, fasten it, and they are done.
This can be done for as little as $2.50-$4 per square foot.
When is a spray foam roof cheaper?
A spray foam roof can be cheaper when there is a minimum R-value that needs to be reached. If you aren’t familiar, R-value is a measurement of how much heat/cool that can pass through a material.
The higher the R-value, the less heat/cool that passes through (which stays in your building), the lower your energy costs will be.
Spray polyurethane foam has an R-value of 6.6 per inch of thickness. TPO and EPDM have an R-value of less than 1.
A single-ply system can achieve the same R-value as a spray foam roof with insulation boards, but they will have to use more material.
Also, single-ply will need to install a tapered system, which means the slope to the drains is created with different heights of insulation, which is expensive to install.
Spray foam is spray-applied.
This means that creating a slope is as easy as reducing the number of passes of foam that’s applied from the perimeter to the drains.
The lifetime costs of each roofing system
One of the biggest advantages a spray foam roof provides is that it’s a renewable system. This means that after the warranty is over (10, 15, or 20 years), all that needs to be done is to add coating on top of the existing roof, add more granules and you’re done.
The cost of a recoat is ½ to 1/3 of the original installation cost in today’s dollars.
This is very different from a single-ply roofing system, which, after the warranty is over, the entire roof is ripped off and fully replaced.
The cost to replace a single-ply roof is 100% of the original installation costs in today’s dollars.
NOTE: The best advice we can give a building owner is to get quotes from roofing contractors that install each system. Ask them to give you the projected costs over 30 years.
What are the drivers of cost for a single-ply roofing system?
A large portion of the cost to install a single-ply system has to do with labor. For a 20,000 sq. ft. roof, 6-10 roofers will be needed to install single-ply, as opposed to spray foam which will use a maximum of 6 roofers.
The equipment needed to install a single-ply roof is basic. All you need is a roller and some hand tools.
The materials needed are the TPO or EPDM, and then the type of insulation board (Polyiso, XPS, EPS, etc.)
What are the drivers of cost for a spray foam roofing system?
The majority of the cost to install a spray foam roof comes in the materials and the equipment used to install those materials.
A spray foam rig includes expensive equipment such as:
- Air compressors
- Heated hoses
- Mixing application gun
The two materials that combine to produce spray foam are an isocyanate and a polyol/resin.
The biggest difference between the cost of the two systems is that single-ply systems are labor-heavy, spray foam roofs are material-heavy.
Other roofing costs that you may not have considered
A spray foam roof can pay for itself in 5-10 years. Although there are many variables, including the current roof condition, the characteristics of the roof installed, HVAC efficiency, etc.
Here’s a PDF from Texas A&M University on how they recouped the entire cost of the spray foam installation through energy savings in 4.5 years:
The difficulty of repair
On a single-ply roof, if the seams come apart and water gets into your insulation, that water will travel horizontally and saturate a large portion of your insulation. A spray foam roof is closed-cell, meaning that a hole/crack will fill with water, but the water will not travel anywhere else.
A repair can cost more for a single-ply system because the area that’s damaged will be larger.
For a spray foam roof, all you need to do is cut out the wet area, dry the area out with a towel, and then fill the area with caulk or silicone. Smooth the area out and you’re done.
Silicone restoration system
A newer roofing system that building owners are learning more about is the SRM (Silicone Restoration System). Instead of tearing off a single-ply roof and installing another roof system, an SRM system can be applied over top, minimizing the amount of tear-off.
Here are some quick stats on SRM systems:
- The cost is around $4-$6 per sq. ft.
- The seams are treated with polyester mesh or self-adhering tape which receive a silicone topcoat
- The entire roof is treated with silicone
- Projected energy savings of 15-35% (more sun reflectivity with white roof vs black roof)
- It’s a renewable roofing system, just like spray foam
- Only the saturated/damaged area of the roof are removed before installation
Recap of single-ply vs spray foam costs
Now you know that the costs of these two roofing systems can vary depending on the situation.
If there’s no minimum R-value to achieve by building codes, single-ply is slightly cheaper.
If there’s an R-value that needs to be achieved, both systems cost about the same.
And if you’re considering the life-time cost of a roofing system, spray foam is more cost-effective.
West Roofing Systems has been installing commercial spray foam roofing systems since 1979. Hopefully, this article gives you the information you need to make the best roofing decision for your building.
What are your next steps?
We have an article that dives deeper into single-ply vs spray foam. In the article, it covers:
- Advantages of each system
- Disadvantages of each system
- How they both get installed
Click here to view the single-ply vs spray foam article.