Insulated Concrete Foundations

Insulated Concrete Foundations “ICF” have interlocking forms that are dry stacked and then they are filled with concrete. These forms lock together much like a Lego brick and can be used to form the structural walls and/or floors of a building.

The most common ICF are manufactured out of Polystyrene Foam but they can also be manufactured out of Polyurethane Foam ,Cement-bonded wood fibre or Cement-bonded polystyrene beads. Once the forms are formed together, re-bar is usually added to give the concrete flexural strength and then the concrete is pumped into the cavity to form the structural element of the walls. The forms are filled in 1-12 foot “lifts” to manage the concrete pressure and reduce the risk of blowout . Once the concrete has cured , the forms are left in place permanently.

Here are some of the benefits in building with ICF:

• ICF building are much more energy efficient then those built with traditional construction methods.

• The form material can easily accommodate electrical and plumbing installations

• Unlike framed walls, ICF has high sound absorption which helps produce peace and quiet

• Higher resale values due to the longevity of the materials

• When wet , concrete and polystyrene do not rot

• It is insect resistant

• It reduces heating and air conditioning costs 50-70%

• ICF creates a structural concrete wall that is up to 10 times stronger the a wood framed structure

Unfortunately, ICF has a few disadvantages as well

• Adding widows,doors or utilities after the building is complete requires concrete cutting tools which makes it harder to do although it requires less structural enhancements to support the new opening

• Depending on the design , an average home can costs 2-3% more than a conventional wood built home

• Minor problems with interior humidity have been know to happen during the first couple weeks as the concrete is curing. Residential dehumidifiers are an easy solution to the problem

• The exterior foam insulation provides easy access for groundwater and insects in polystyrene based forms. To help prevent these problems, some manufacturers make insecticide treated foam forms and promote methods for waterproofing them

Building with ICF can sometimes add 3-5% in construction cost compared to using wood frame, however the energy savings will usually result in much lower utility costs. Building with ICF below grade for typical basement forming should come in at about 40% less due to the labour savings from combining multiple steps into one. Above grade construction is a little more expensive but it becomes cost effective when adding large openings. In wood frame buildings, large openings require large headers and support posts but in ICF additional re-bar is all that is typically needed.

Nathan Pile

Barrie Home Inspector