ICF Myths Foam Beads

Mixing Foam Beads with Concrete After Cutting

"Is there really a benefit to cut through a wall to create an opening? It seems that I've heard that the foam beads that fall into the cavity would affect adhesion of the wall concrete to the footer."

Actually, because all of our concrete is vibrated internally, we have found that the beads tend to float with the consolidation. I guess we are kind of making a bit of 'Aerated Concrete'. It may effect the strength though, and I believe that you are right about the excessive beads in the formwork. The small amount we currently put in from limited cutting is not too detrimental, (I hope), however, I think you have a very, very good point here.

In our opinion, there are no advantages to cutting the forms when in place on the wall. We refrain from this action for several reasons. 1). The wall is subjected to unnecessary rocking that can lead to troubles in wall alignment and plumb. 2). The foam beads that drop inside the wall cavity ARE detrimental to the envelope of the wall. 3). This practice usually requires cutting reinforcing steel while on the wall also. Cutting the bar while in place can be cumbersome. 4). Why not just build the wall per the plans and specs without having to “go back” to cut openings, etc.? This approach of cutting openings later creates more waste and does not look as if the project is being constructed in an organized, professional manner.

We routinely remove leaves, mud and foam beads when we rinse the cavity prior to placing concrete. We remove this debris using a garden hose and weep holes. If we notice any debris inside a wall, we insist on cleaning it prior to placing concrete. This should be 'the norm' for all ICF contractors. If any debris is allowed to remain on the footing under an ICF wall, the bond between the ICF wall and the footing will be, for the most part, non-existent. Even a light layer of fine mud will be just enough to allow for water and bugs to move right into the structure. If there are large piles of foam bead “dust” present, then even small rats can migrate right through the wall, as well as a little air infiltration.

The idea that vibrating the concrete will cause the debris on the footing to “mix” with the concrete is simply not true. A house in Texas had to be completely removed from the slab (destroyed), reformed and poured a second time after the owner discovered that over half of the concrete walls were kept as high as 3” off of the slab. This was caused by the installation contractor. The contractor cut the blocks while in place on the wall, allowing the foam “dust” to enter the wall cavity. Had the contractor cut weep holes in the bottom of the wall and either washed the debris out or blew the debris out with air, the problem would never have happened.