Insulated Concrete Form (ICF) Construction

Site poured concrete foundations have been with us for over 100 years in our modern construction however the technology dates back to ancient Roman times. The ability to easily shape concrete through the use of forms to carry the load of the structure above is one of the reasons we have so much variety in the types of buildings around us. 

A new type of concrete form system called insulated concrete forms (ICFs) has recently had code changes enacted across North America that will allow us to build foundations faster, stronger, with less waste, and improve insulation in our homes. These new ICF foundations will change the way people look at building sites and the way builders build.

What is an Insulate Concrete Form (ICF)?

ICF's are pre-made blocks of hollow ridged foam that are stacked together on the building site like Lego to create the shape of the foundation. Concrete is then poured inside the ICF blocks for structural support. Unlike traditional concrete forms, the ICF blocks remain in place as part of the permanent construction providing advantages such as:

Close up detail of ICF forms with rebar added ready for concrete pour

  • Increased insulation value - The ridged foam materials have very high thermal resistance values greatly increasing the insulation properties of the concrete alone
  • Improved Sound Resistance - The foam also transmits less sound improving occupants comfort
  • Structural Rigidity - The shapes of the blocks can be made to give additional friction for the concrete improving the rigidity and structural capacities of the concrete. This can be further improved with rebar added on site.
  • Utilities - Pluming and electrical can be added inside the walls of the building prior to concrete being poured or can be added in the foam layer
  • Water Resistance - The ridged foams used for ICF blocks will help resist water however they are not intended to operate as primary water shedding surfaces.

Advantages Over Traditional Construction

ICF construction offers advantages over traditional site built forms.

Full site view of ICF blocks assembled and ready for concrete

  • Less Customization - As ICF forms are built like lego blocks, builders don't need to build custom forms for each home.
  • Less Skilled Labour - As there is less customization of the site, less skilled labour can be used to help build the walls reducing building costs. On-Site supervision of all work should still happen under experts that understand the building codes and manufacturer requirements.
  • Faster Construction - ICF forms can be constructed faster than traditional forms with more readily available labour. Plus, electricians and plumbers can pre-install some segments for faster installs in the home.
  • Less Waste - There are no forms to dispose of at the end of the concrete pour as the ICF forms remain in place

What Home Inspectors Look for with ICF

Home inspectors should be able to identify for their clients if a home is an ICF home and the advantages that this system offers. As ICF systems are still poured concrete foundations, home inspectors should still be looking for any traditional signs of concrete wall system failures.  Cracks will not be readily visible in ICF systems as the foam exterior will block views so inspectors may need to look for other visual clues such as wall movement and other structural stresses for any signs of wall system failure.

Final Thoughts

ICF construction has only been entering mass usage in the last decade or so which does present some risks to home builders and owners. However, the energy and comfort benefit of ICF construction are compelling reasons to consider this newer forming method as it helps deliver the goal for home buyers to have a home that is safe and solid.

Code Update

In the 2014 building code changes adopted by British Columbia, a requirement for continuous insulation from below grade to attic will now be required. As ICF forms provide an effective insulation below grade, builders may more commonly use these systems to meet energy efficiency code changes. See our 2014 code change summaries here.

By James Bell - Owner/Operator of Solid State Inspections Inc.