ICF block, short for Insulated Concrete Block is an EPS foam form with a middle structural core that rebar steel and concrete are placed. A 6” core results in an R value of 22. Placing the first course of the lego style building block is critical. As the first foundation layer, it is critical to attain a level and square placement. This applies in all directions of the x,y and z alignments. In our build, each block is 18” so three courses were needed to get to finished floor height and have the required 4’ below grade.
Thank goodness for instruments that shoot a laser line at the required elevation to ensure accuracy. For the horizontal and vertical measurements, good old string makes a great way to ensure no part of the wall is bowed in or out over its length and height. To ensure the concrete flows through the form and fills in and around the rebar, a special concrete mix is required using 3/8” stone (not the usual ¾”) and water to make the concrete into a slurry known as a slump rating. For our build it was a rating of 6. When complete, the concrete takes 7 days to cure and set. What once was a light weight, easy to handle EPS foam form is now a solid, structural, impenetrable foundation wall. And to avoid having to core drill through concrete, sleeves are placed in the wall before the pour to all for plumbing drain outlets and of special consideration to canaries, mechanical services. But more on that later.