Since ICF blocks or panels are the forms, time is saved over traditional concrete by not having to set up and strip down concrete formwork. ICFs are also light and easy to install by hand, lending to additional time savings.
While there is a learning curve for first-timers, studies have shown that this learning curve can be overcome in 3 hours or less. With a very level footing and general construction proficiency, setting ICFs can be a do-it-yourself task. Leveling, shimming and shoring are keys to a plumb and square foundation wall, which will (literally) set the stage for the balance of the project.
ICFs allow concrete pours to occur at lower temperatures as the insulation protects the curing concrete from freezing. Concrete can be poured in ICFs at ambient temperature as low as 10°F, requiring only the top of the form to be protected with insulating blankets.
With ICFs, the insulated surfaces inside and out provide the backing for finishes. While concrete foundations may be left unfinished, ICF interiors need to be covered with drywall or plywood for fireproofing. Exposed exteriors are ready for a stucco-style finish while below grade, the insulation needs to be covered with an appropriate waterproofing membrane. The exterior finishing and waterproofing costs may be included in ICF pricing estimates.
Insulation is recommended for all types of foundations for energy efficiency and improved indoor air quality. However, it is not always included in pricing estimates by contractors using traditional construction techniques. Before comparing ICF and traditional concrete foundation quotes, make sure interior and exterior insulation are included. See the October 2008 post to learn more about Knickerbocker Group's best practices for exterior insulation, drainage planes and waterproofing.A potential drawback of some brands of ICF may be termite / ant control. ICFs have even been banned from use as basements or foundations in some states with high levels of termite infestations. As with a concrete foundation with exterior insulation, a barrier can be installed along the top and below the sill plate. While ants or termites may travel in unseen channels within the insulation, the barrier will force them to seek a more visible route on the outside. Some manufacturers are also beginning to work with boron-impregnated polystyrene.
Be aware that ICF costs may be initially higher than for traditional foundations, but some of that extra cost is reduced when the insulation is added to the traditional foundation. Further savings come from the energy efficiency during the use of the structure. A true apples-to-apples price comparison is difficult to calculate, but one manufacturer estimates ICFs are about $2000 more on average at the "ready for drywall" stage of construction. This is comparable to the order of magnitude found at Sonne Ledge.
Overall, our experiences have shown that for both ICF and traditional concrete foundations, the 'weight' of the benefits and drawbacks changes depending on the project site, homeowner's needs and building design parameters. Each home site needs to be evaluated independently to decide which one is the most appropriate and cost effective choice.Please check out the links to the right if you are looking for more detailed information on ICF construction. Feel free also to contact us at 207-633-3818 or info@knickerbockergroup.com.
