Why DIY Spray Foam Might Be a Bad Idea

Updated: Jun. 29, 2021

Here's what you need to know about DIY spray foam and why it's generally not a good idea.

Yevhenii Orlov/Getty Images

Typically, when it comes to DYI Spray foam, we’re talking about the disposable container style or “Froth-Kits.” But these kits are not always as simple and safe as they seem. Here’s what you need to know about DIY spray foam and why it’s generally not a good idea.

Spray foam comes in two parts, one side Polyol (B Side) and one side isocyanate (A Side). These two chemicals need to be precisely mixed in perfect conditions. Anyone attempting to spray two component polyurethane foam will need to have proper respiratory, eye, and skin protection.

Compounding the difficulty of these SPF “kits” is the fact that the viscosity of the two chemicals are different. One is thicker than the other, which makes maintaining a perfect mix throughout the process extremely difficult.

Conditions Need to be Perfect

Further exacerbating the trouble with these kits, the temperatures and mixture of the two chemicals need to be exactly as specified on the application instructions.

If it just so happens that all these conditions have been met, the spray substrate needs to be at the proper temperature and free of dust and debris.

Moisture levels of the spray surface need to be under 18% moisture content or problems will arise.

Note that while spraying, as the level of material in the disposable containers decreases, the pressures also go down. Once the pressures are off balance, it’s all but impossible to produce a true “on ratio” foam. This is what we, the professionals, call “bad foam”. This can begin to happen once the material levels drop below half, especially if the temperatures aren’t perfect.

In others words, even if all the spray surface conditions and preparations are perfect, there’s still risk of spraying a bad product.

Identifying off ratio foam or “bad foam” is trickier than one would think. Sometimes the foam looks perfect to the naked eye, but soon thereafter the application, uncured areas will show through or shrinking will occur.

The health risks of spraying “off ratio” foam can be significant.

If you insist on spraying the disposable spray foam containers, we suggest only using them on very small repair and/or projects, follow the instructions closely, and make sure all safety and health precautions are taken.

How Much Money Can You Save With DIY Spray Foam?

The average cost for a disposable closed cell spray foam kit or “Froth-Kit” advertised to spray 650 square feet at a one-inch thickness, is typically around $800. That’s just shy of $1.24 a square foot.

A typical price quote, seen from a trained spray foam contractor, is around the same price (per square foot) at one inch. That includes the spray foam insulation, surface prep materials and clean up.

The high cost coupled with possible health risks are why we highly recommend hiring a trained professional when it comes to spray foam insulation.

About the authors:

Ken Wells is a SPF contractor, advocate and co-owner at Elite Insulation & PolyPro out of Broadway, Virginia.

Bill Bilben is a SPF contractor, advocate and founder of the website SprayFoamww.com as well as the Spray Foam World Wide Facebook group dedicated to connecting professionals in the industry through networking, education, support and information.