Spray foam roofing is growing in popularity and challenging EPDM, TPO, built-up roofs and other commercial (and some residential low-slope roofs) roofing options for market share.
The technical name is SPF roofing, aka spray foam polyurethane roofing.
This is your comprehensive buying guide.
What is Spray Foam Roofing?
SPF foam roofing is a sprayed-on roofing material that features three layers of material. Specifics of how it is applied are in the next section.
Base SPF: The primary layer is 2-part spray foam polyurethane (SPF). The material has been used since the 1960s in various applications, so it is a known commodity with clearly defined pros and cons.
The spray foam is a mix of two substances, a polyol resin and an isocyanate. They are combined onsite in a mixing spray gun and applied.
This is closed-cell foam, which makes it waterproof and gives it a higher R-value of 6.6 per inch vs. about R-3.5 per inch for open-cell foam.
The result is a seamless and waterproof roofing material.
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Topcoat layer: The installed foam is coated for protection since bare SPF will begin to deteriorate from UV radiation in a few days if not treated. One or more coats are applied. Elastomeric coatings in current use are acrylic, silicone and urethanes. Most spray foam roofing contractors prefer silicone.
Granules: Similar to asphalt shingles, SPF foam roofing is covered in granules that serve to reflect UV. But they also create traction for walking on material that would otherwise be slick.
Did you know? Many high-end SPF roof coatings meet CA Title 24 Energy Code requirements for low slope roofs. Look for CoolRoof label to attain significant energy savings and improve the comfort of your home/building.
Spray Foam Roofing Application Process – What to Expect
Here’s a look at how spray foam roofing is applied and what you can expect as the project proceeds from start to finish.
Before quoting the price of SPF roofing, the contractor wants to understand the condition of the roof and what preparatory work is involved.
Damage must be repaired. If the roof has leaked and the roof deck is saturated and damaged by water, affected materials must be removed. Similar materials are used to repair the damage.
For best adherence of the SPF, the existing roof must be clean. Common methods to clean a solid roof such as mod bitumen, EPDM or TPO are to use air pressure to blow away debris and dirt or to power wash the roof.
The stone and gravel ballast used to hold down single-ply roofing membranes are removed with a dry vacuum. If the underlying membrane is significantly dirty, then it is sprayed for cleaning, and a wet/dry vacuum is used to remove the material.
The chemicals are stored in separate tanks and pumped through high-pressure hoses with heat applied. The materials enter a mixing spray gun, and the applicator sprays on a thin coat of the combined materials.
The thin coat of SPF roofing expands, increasing about 30 times. An ideal thickness is about 1.5 inches for most applications. At times, a thicker coat is applied primarily to produce a higher R-value, or insulation value. There’s more on spray foam roofing R-value in the pros and cons below.
The silicone, urethane or acrylic topcoat is sprayed on in one or two coats. The finished thickness of the topcoat is 20-30 mils, with one mil equal to 1/1000 inches. It’s thin stuff, but very hard and resilient.
This material is scattered onto the roof by a crew member following behind the person spraying on the topcoat. This ensures that the granules are applied to a wet topcoat, and they become embedded and adhered as the topcoat dries.
What Types of Roof Surfaces Can Be Covered with Spray Foam Roofing?
One of the impressive benefits of spray foam roofing is that it is used to cover a range of common commercial roofing materials with little preparation.
TPO: A coverboard is installed over the TPO and fastened to the roof substrate. The spray foam roofing is applied directly to the coverboard, which is commonly 1/2″ high-density fiberboard (HDF).
EPDM: Spray foam roofing is sprayed directly onto EPDM roofing that is fully adhered and more than 5 years old – it takes that long for the oils to dry out of it, so the SPF roofing will adhere.
For EPDM less than 5 years old and for mechanically fastened EPDM, a cover board is installed first. Ballasted EPDM must be cleared of ballast and topped with cover boards.
Modified Bitumen / Mod Bit: Spray foam roofing can be applied directly to mod bit – no coverboard required.
Built-up Roofs: Yes, spray foam roofing can be applied directly to a smooth or gravel-surfaced built-up roof since the layers are fully adhered. When the top gravel is loose, it must be removed, usually with a commercial wet vac.
Metal: This is an ideal substrate for spray foam roofing. If the roof is showing rust, a rust inhibitor is applied before the SPF.
There are few options for spray foam roofing installations.
Topcoat: As mentioned, elastomeric silicone is the preferred option since it flexes better to handle expansion and contraction with changes in temperature. However, some contractors prefer acrylic or urethane for their slightly better strength and protection against punctures.
Color: Silicone topcoat is offered in a few limited colors – white and gray tones.
Thickness: The best practice is a single application of spray foam roofing to 1.0 to 1.5 inches. However, some SPF roof contractors in very hot and very cold climates do offer greater thickness to increase R-value.
Recoating a Spray Foam Roof
The 2-part polyurethane foam lasts indefinitely. But the topcoat begins a slow process of deterioration and thinning.
The coating is measured during semi-annual inspections. Depending on climate conditions, the topcoat thins to about 10 mils in 10-20 years. This is the time recoat the roof with fresh silicone, urethane, or acrylic topcoat to restore it to 20-30 mils thickness.
Fresh granules are applied too.
Most contractors provide a renewed warranty with a recoating application.
Additional maintenance and repair information is provided below.
On average, spray foam roofing cost between $4.75 and $9.50 per square foot installed.
That’s a wide price range, but the cost factors explained next will help you narrow your “guesstimate” for what you’ll see when you get pro quotes for the work.
Basically, if there’s little prep work needed, your cost will be on the low side. If your roof is a wreck and needs additional work, expect costs near the upper end of the spectrum. Smaller sized roofs (residential low-slope roofs typically measure between 1,000 and 2,500 square feet.) will likely fall within the higher end of this range.
While prices are volatile for all building materials and remodeling/commercial construction work these days, your cost should still fall somewhere within $4.75 – $9.50.
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Exceptions: note that your quoted SPF roofing costs can be higher when there’s additional work required that falls outside of the scope for a typical project. You can also see higher quoted prices in the high cost of living areas (HCOL) like Los Angeles, San Jose, San Francisco Bay area, Seattle, Boston, etc. where/when the demand for roofing and home remodeling pros may exceeds the available supply.
Factors are listed in the left column and explained below.
|Low Cost||Average Cost||High Cost|
|Cost Factor||$4.75 – $6.50/sq. ft.||$5.75 – $7.75/sq. ft.||$7.75 – $9.50|
|Roof Repair Needed||None or Little||Moderate||Extensive|
|Roof Size||More than 40,000 sq. ft.||20,000 – 40,000 sq. ft.||Less than 30,000 sq. ft.|
|Ballast Removed||Yes or No||Yes or No||Yes|
|Cover Board Needed||No||Yes or No||Yes|
|Roof Height/Access||Low/Easy to Moderate||Average/Moderate||High/Difficult|
|Roof Penetrations||Few||Average||Average to Many|
|Foam Thickness||1.0 – 1.5 Inches||1.0 – 1.5 Inches||1.5 Inches or More|
|Recoating Cost||$1.50 – $1.85/sq. ft.||$1.75 – $2.15/sq. ft.||$2.00 – $3.00/sq. ft.|
Read the breakdown of component costs below.
The cost factors are meant to represent the general characteristics of the roof. In some cases, not all apply to all roofs in that price range.
For example, a roof over 40,000 square feet could fall in the High Cost range if needed repairs are substantial.
It’s unfortunate for the owner of a commercial building not to realize that it needs a new roof until significant deterioration has set in, but it happens. Even well-maintained roofs often need some repair prior to being covered in spray foam roofing.
The more of the roof deck or substrate, the material beneath the roofing material, needs to be replaced, the higher the project cost per square foot will be. Pretty straightforward.
According to Western Roofing Systems, “economies of scale start at around 20,000 square feet.” The bigger the roof, the lower the cost per square foot.
All loose material including ballast, EPDM that isn’t fully adhered and gravel on a built-up roof must be removed and disposed of or recycled – at significant cost.
Cover Board Added
TPO, as one example, is a slick roofing material that makes it difficult for SPF foam to adhere to. As a result, a cover board, or coverboard, is first attached through the TPO to the roof deck. As noted, 1/2″ HDF chipboard is the most common cover board option.
Roof Height and Access
When a roof is low and can be accessed easily with a lift from outside or from stairs inside, time is reduced – and cost is too. The higher the roof and the more time-consuming it is to access it, the higher the spray foam roofing cost per square foot.
Installing SPF roofing around vents, pipes, HVAC equipment stands, and other penetrations and protrusions goes pretty fast when compared with installing EPDM or TPO around them. This is a minor cost factor. However, the more obstacles there are, the higher the cost.
SPF foam is an effective way to add insulation value to any building. With an R-value (resistance to heat transfer) of 6.6 per inch, R-10 can be added to the roof with 1.5 inches of spray foam roofing and R-20 with 3 inches. The Department of Energy recommends R-30 as a minimum.
In hot and sunny weather, another inch or two of spray foam roofing slows heat transfer into the building. In cold weather, the extra material reduces heat loss. In both cases, the building stays more comfortable and the operating costs for HVAC equipment are lower.
Spray Foam Roofing Recoating Cost
The cost to recoat spray foam roofing is $1.50 to $3.00 per square foot.
The topcoat on the spray foam roof prevents UV rays from damaging the SPF foam. It is critically important.
Once the topcoat thins to about 10 mils, it should be sprayed again to increase thickness to 20-30 mils. This point occurs between 10 and 20 years after installation.
*Recoating the foam can be done indefinitely, as long as the SPF is in good condition.
The primary cost factor is how much topcoat is applied.
If there are cracks in the foam, they must be cleaned and caulked before recoating the roof. This is an added expense above the recoating cost given above.
Let’s compare costs of SPF roofing with those types residential and commercial building owners typically also consider.
EPDM, TPO and BUR/built-up roofing.
|Material||Low Cost||Average Cost||High Cost|
|Spray Foam Roofing||$4.75 – $6.50/sq. ft.||$5.75 – $7.50/sq. ft.||$7.75 – $9.50|
|EPDM||$5.00 – $6.50/sq. ft.||$6.50 – $7.75/sq. ft.||$7.75 – $9.75/sq. ft.|
|TPO & Mod Bit||$5.50 – $6.75/sq. ft.||$6.50 – $8.00/sq. ft.||$8.00 – $10.00/sq. ft.|
|Built-up Roofing (BUR)||$5.35 – $6.75/sq. ft.||$6.50 – $8.50/sq. ft.||$8.50 – $10.50/sq. ft.|
A properly maintained SPF roof lasts for many decades – perhaps indefinitely.
Here’s a look at 40+ years and the costs incurred if using today’s prices.
Consider a 25,000 square foot roof using current average costs for initial spray foam roof installation, recoating and inspections plus minor maintenance as part of the inspection.
For comparison, the table assumes that recoating is needed in 15 years, though the range is 10-20 years based on climate factors and the thickness of the original topcoat layer.
|1||Roof Installation @ $6/sq. ft.||$150,000|
|2-15||Inspections @ $0.04/sq.ft.||$1,000/year = $14,000|
|16||Recoat @ $2.50/sq.ft.||$62,500|
|17-30||Inspections @ $0.04/sq.ft.||$1,000/year = $14,000|
|31||Recoat @ $2.50/sq.ft.||$62,500|
|32-45||Inspections @ $0.04/sq.ft.||$1,000/year = $14,000|
Now, let’s compare the long-term costs for single-ply roofing using average costs for EPDM (10 years) and TPO (20 years) with an average lifespan of 15 years.
|EPDM & TPO|
|1||Roof Installation @ $5.75/sq. ft.||$143,750|
|2-20||Inspections @ $0.04/sq.ft.||$1,000/year = $19,000|
|21||Roof Installation @ $5.75/sq. ft.||$143,750|
|22-41||Inspections @ $0.04/sq.ft.||$1,000/year = $19,000|
|42||Roof Installation @ $5.75/sq. ft.||$143,750|
|43-45+||Inspections @ $0.04/sq.ft.||$1,000/year = $3,000|
As you can see, the potential savings over 40+ years are significant, to say the least, with a spray foam roof. To put it another way, EPDM and TPO have a long-term cost 50% higher.
SPF Roofing Longevity
Spray foam roofing can be expected to last 40-50 years and potentially much longer with consistent maintenance before the topcoat layer becomes compromised and allows the foam layer to begin deteriorating.
Here are industry averages for the roof types discussed above:
- Spray Polyurethane Foam: 40+ Years
- TPO: 15 to 20 Years
- EPDM: 10 to 15 Years
- BUR/Built-Up: 10 to 20 Years
Spray Foam Roofing Warranties
The length of the warranty depends on the warranty offered by the manufacturer of the foam and the thickness of the topcoat layer of elastomeric silicone, acrylic or urethane.
Common warranty lengths are:
- 10 years for a 20-mil topcoat
- 15 years for a 25-mil topcoat
- 20 years for a 30-mil topcoat
To maintain the warranty and ensure any claim will be honored, the spray foam roofing must be annually inspected, and any damage must be repaired. Details are in the next section.
Maintenance and Repair
The roof should be inspected yearly and after major storms that produce large hail or wind-blown debris.
Damaged foam is cut out. Large areas are filled with new foam. Small damage is filled with an elastomeric/flexible waterproof caulk.
Under normal conditions, the foam might experience minor cracks after 10-15 years, and those cracks should be filled with caulk.
Is it Worth the Money – Pros, Cons and ROI
SPF roofing costs a little more than BUR and single-ply roofs like TPO and EPDM. However, the lifetime cost is significantly lower because the foam can be renewed with a fresh topcoat rather than having to reroof the building. See the Tables above for a cost comparison over 40+ years.
Before we look at the ROI, or return on investment, here are the pros and cons of spray foam roofing.
- Not prone to damage from wind, hail or wind-blown debris
- Seamless and waterproof, whereas seams in some single-ply roofing options can come apart and be a major source of leaks
- Easy to maintain and make minor repairs
- Can be refreshed rather than having to be reroofed
- Provides an R-value of 10 on standard installation – and can be applied in a thicker coat for better insulation value – compared with almost no insulation value from EPDM, TPO, BUR or steel
- Installs much faster than EPDM, BUR or TPO and is self-flashing, meaning that the waterproof materials are used to coat around and up any protrusions, eliminating the need for metal flashing around vents, pipes, parapet walls, etc.
- Slightly higher initial cost when compared with some other common commercial roofs
- If the topcoat is allowed to get too thin or is damaged, UV will begin to cause deterioration of the foam, which can lead to expensive repairs or the need to reroof the building
- More prone to puncture damage than BUR and roofs with gravel and stone ballast
- Installation requires a temperature of 50F or higher and low-wind conditions
- Overspray of the topcoat is possible even in light winds, so precautions must be taken to prevent damage to nearby vehicles
- Not as well-known as EPDM and BUR, so potential buyers of the building might need to be educated on spray foam roofing’s benefits
The ROI, or return on investment, is considered very good with spray foam roofing for two primary reasons.
It provides high R-Value: SPF roofing provides the highest insulation value, usually about R-10, of any commercial roofing material.
It is renewable: The roof can be refreshed every 10-20 years for 50+ years, rather than requiring a tear-off and reroof. This significantly reduces the long-term/lifetime cost of the roof compared to BUR, TPO, EPDM and PVC.
Here are common questions with brief answers. Some Qs are answered in more depth in the content above.
How much does spray foam roofing cost?
Cost ranges from $4.75 to $9.50 per square foot based on any necessary roof repairs and prep work before installation, size of the roof, ease of roof access, and the thickness of the topcoat.
What type of topcoat is used?
Elastomeric materials, meaning they flex with normal expansion and contraction of the roof due to temperature changes.
The most common is silicone, but flexible, waterproof urethane and acrylic are also used.
How much does it cost to recoat the roof?
About $1.50 to $3.00 per square foot, and it is done every 10-20 years based on initial thickness and local climate factors.
What is SPF roofing?
SPF stands for spray polyurethane foam, and that’s exactly what spray foam roofing is.
What materials can be covered with spray foam roofing?
It can cover most commercial roofing such as BUR, steel, TPO, EPDM and PVC can be covered without a tear-off. Some, like super-slick TPO, require an HDF fiberboard to be installed first.
How long does spray foam roofing last?
The best answer is “indefinitely” when properly maintained and recoated as needed. You can expect an SPF roof to last 40 or more years.
Is this a DIY roof?
No. Large crews use expensive equipment for most jobs.
How long does it take to install spray foam roofing?
Most contractors send a large crew to do the work. On most projects, between 6,000 and 8,000 square feet of roofing can be applied per day once the initial work of prepping and repairing the roof is complete.
Typical 20,000 square feet roof (commercial size roof):
Up to a week: Repairs, if needed.
2-3 days: Coverboard installation, if needed.
3-4 days: Spray foam roofing installation and cleanup
How green is it?
The material is quite environmentally friendly in these respects:
The R-value makes it Energy Star compliant and reduces loads on HVAC equipment. It also complies with LEED and International Code Council (ICC) requirements.
Most commercial roofing can be covered rather than torn off and disposed of in a landfill.
The foam is low in volatile organic compounds, VOCs.
The roof has algae on it. What’s the solution?
Light power washing with a 3:1 solution of water and bleach is a common cure. Consult the installation company about cleaning the roof to be sure the process is approved and will not damage the roof or void the warranty.
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