Block Basements: My Pick

For a Foundation

There is no perfect foundation, older homes and stone foundations had their good and bad points and they were the only real choice for hundreds of years. Block foundations started to show up around WW1 and poured foundations were actually available before WW2. They did not become popular in residential construction until the 80’s however. In the 1940’s, a Swiss gentleman invented what we know today as the ‘’Insulated Concrete Form’’ or ICF as it’s called. In Canada a small company in Cobourg called ‘’Blue Max” really started the development and residential use of ICF for not only basements but entire homes.

By now you have guessed my favourite for not only basements but entire walls are ICF. ICF blocks are formed using commonly expanded polystyrene or extruded polystyrene. Hollow in the centre, they are fitted together not unlike the old ‘’mini-bricks’’ that were popular as children’s building blocks. Rebar is interwoven through the forms as required by the ICF block manufacturer and then concrete is pumped into the block cavity and you now have a solid concrete, foam insulated wall.  When foundation walls done with this method they are warmer, the number one reason I recommend ICF for a foundation. You immediately get an insulation value of no less than R25 and some manufacturers claim up to R40 & 50; that may be a bit of a stretch. ICF walls are protected from freezing or rapid drying at lot more easily than a poured foundation. You should apply a complete waterproof membrane on the exterior and the interior of the ICF blocks must now be covered in drywall, its code.

At one point the argument was that ICF foundations were a lot more expensive, and it was true, today this myth has some holes in it. When you factor in the cost of adding a wood partition, paper barrier, insulation and air barrier to a poured foundation the gap closes real quickly. The cost of ICF blocks has dropped; there are a number of manufacturers making these now, the old story of competition making the prices sharper. Installing an ICF foundation, provided you have taken the manufacturers course is not difficult. That said attention to detail and having a skilled installer on site who can save assembly time and prepare the walls is worth the money. I have seen an ICF wall that had a ‘’blow-out’’ during the concrete pour and it’s not pretty, in fact it’s a mess fixing and cleaning it up.

While I am a fan, I am also a realist and ICF is not the perfect foundation or so it is sold by some manufacturers. If you have an ICF foundation with a conventional frame home you will still hear the neighbour’s loud party, this is a good foundation but the sound transmission will still pass thru a frame home. One big grumble I have with some ICF co.’s and their advertising is the claim it will even the heat distribution, that’s a myth. The ICF foundation will be warmer and may possibly reduce the size of HVAC system you need but it has nothing to do with even heat distribution. My last comment is the claim it will reduce your fire insurance. Maybe a little if the entire home is ICF right to the rafters. As an ICF basement I have my doubts it will make a dramatic difference if at all.

From my experience, an ICF basement foundation with proper external waterproof liner and drainage infrastructure installed, walls covered in drywall then the quality of air should be improved, especially if the home has an operational HRV. A dry basement will have a positive effect on the entire indoor air quality in the home. The major benefit we hear from our clients, the basement is warm and comfortable, and that’s what matters to them.

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