Exterior Foundation Waterproofing: Closed-Cell Foam
Builders and Contractors are required by the State Building Code here in Massachusetts to apply a waterproofing membrane on the exterior of foundations in all areas that will be sub-grade (under the ground after backfilling.)
The most common products are asphalt and rubber based. As an experienced waterproofing professional I have seen these membranes fail quite regularly. Of course the quality of the spray and experience of the installers is key to a proper installation.
About 90% of the time the waterproofing membrane is covered with 1″-2″ of polystyrene insulation and it is usually attached by shooting nails into the foundation. These 2″ nails being shot into the foundation are a breeding ground for future foundation wall cracks.
So now what???
One inch of Closed-cell spray foam insulation is an approved vapor barrier with permeability being at, or below most asphalt and rubber based waterproofing membranes on the market. Closed-cell foam is approved for exterior and sub-grade applications.
One inch of closed-cell foam has an insulation r-value of between 6-8 depending upon the product. There are endless companies that offer a soy-based closed-cell spray foam insulation which are among the greenest products on the market. Adding a second inch of closed-cell spray foam will bring the r-value to 13 or higher.
So is it cost effective???
There is no doubt in my mind! As stated earlier I am also a waterproofing professional and have not only applied asphalt/rubber based products, I have priced and sold these projects.
These applications range from $.80/sq’ to $2.50/sq’ based on the product, quantity and whether insulation boards are added.
Applying closed-cell foam instead will cost from $.70 to $1.50/sq’ based on quantity and thickness.
So why not let this game changing product do just that! Out with the old and in with the new. It is time that builders learn the benefits of spray foam insulation and all of it’s uses.


