Here at Steven Baczek Architect, we regularly spec 10-in.-thick, steel-reinforced concrete foundation walls, but some projects call for deviation from our norm. This detail is from a house for which we went with a Logix Pro insulated concrete form (ICF) block foundation. One of the benefits of an ICF assembly is that insulation is integrated; the thermal resistance of this 11-3/4-in.-wide block with 6-1/4-in. core is R-25. Also, compared to our standard 10-in. foundation wall this system uses 38% less concrete, which is in line with reducing embodied carbon in our buildings. We have found, too, that ICFs are no harder to work with than the materials that go into our typical assembly.
Because this is a basement wall, groundwater management is critical. Although the 2-3/4-in. expanded polystyrene foam (EPS) that flanks the block walls is hydrophobic and the concrete core is continuous, we added Tremco’s Tuff-n-Dri spray-applied waterproofing to the exterior of the ICF blocks, as well as the exterior face of the footings.
We are confident that the waterproofing product will keep water out but to ensure that, it needed to be protected against the backfill stage of construction. We installed a 2-3/8-in.-thick vertically oriented rigid protection board, which also supports drainage. It reaches down to the top of the footing, helping to move water away from the foundation via a 4-in. perforated drainpipe at the exterior of the footing.
Together the protection board, perimeter drain, and free-draining backfill provide a “down and out” strategy to direct ground water away from the foundation before it challenges the waterproofing membrane, which is the final barrier to water intrusion.
A second perimeter drain sits to the inside of the foundation wall. Here we did something a little different, using a bed of insulating…
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