Spray Foam Over Metal Roofing: Cost, Benefits & Installation

How much does it cost to install spray foam over an existing metal roof?

The cost to spray foam over a metal roof is usually in the $5-$10 per square foot.

Variables that influence price include the distance from the contractor, how much foam they want/need, the length of the warranty, and the condition of the existing metal roof.

There are some extremes that can be well past that mark.

For example, on one recent project, the space between the ribs was very deep.

It was cost-effective to insert wood panels in-between each rib, and then spray over everything, as opposed to spraying an incredible amount of foam inside each rib to ensure water flows correctly.

The same roof needed all new custom-fabricated, flanged gutters.

That roof was about $20 per square foot.

Why choose spray foam over other options?

There are really only four options available:

1) Install spray foam

2) Install coating system

3) Flute-fill and TPO

4) Complete tear-off and replacement

Metal roof owners/managers choose spray foam because coating the roof (the least expensive option) is not an option.

The roof may be too rusty or in too poor of shape to coat, so spray foam is the next best option.

Some people choose spray foam because the current roof has no insulation and foam offers the best R-value of any commercial roofing insulation available.

Spray foam has an R-value of 6.5 per inch.

Owners rarely choose flute-fill and TPO because it’s very expensive.

Some people like TPO for whatever reason, and that’s the reason they go that route.

I’m not sure what the price is for a complete tear-off and replacement, but it’s likely north of $15 per square foot. It’s a lot more when you throw in business/operation disruptions.

Metal roof owners choose spray foam because it’s fluid-applied. It covers up all the seams and fasteners that are the usual culprits of metal roofing leaks.

And it comes with a renewable and transferable 10-20-year warranty.

What issues could arise from installing spray foam roofing?

The only issue that can happen is with the contractor.

- Can they install a good spray foam roof?

- Do they know the science of foam, and how much experience do they have?

If you choose a bad contractor, they could install bad foam; it blisters, they don’t take care of it, lawyers are involved, and you go down that road.

There’s absolutely nothing wrong with the system; it’s just making sure it’s installed correctly.

This article goes into depth on the red flags of a commercial roofing contractor and how to ensure you don’t choose a bad one.