With the Ottawa region built on leda clay, the weight of a house can compress the soil and make the house sink. Past homeowners had trouble with homes sinking; today's homeowners have foam to look forward to solve the problem.

Foam under the ground can add $5,000 to $7,000 to the cost of a home, but the initial cost gives a larger payback when it comes to ensuring the home stays stable decades down the road.

In Ottawa, Tartan Homes also uses the foam in place of chipboard or plywood in wall buidling. They also use sprayfoam in some places to improve energy use. It is part of the evolution of home building technology.

The huge blocks of foam weigh about 40 kilograms apiece.  

In some areas, homeowners won't be able to put in pools - or may have some extra work when building a fence - but builders hope that most won't notice the difference.