The foundation of the FHB House project in Rhode Island was designed and built with performance and water management in mind. You can read more about the theory and logic behind its design here. Builder Mike Guertin and his small crew does all of the foundation work themselves. This drove their product selection and the details of the foundation’s assembly to ensure a solid base for the framing to come.
Here’s a glimpse at its construction from earlier this summer.
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The foundation footings are formed conventionally. Instead of relying on a keyway to secure the foundation walls to their footings, Guertin relies on rebar. Like the rest of the home, the entire foundation plan was reviewed and stamped by an engineer.
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Parts of the foundation will be treated as a frost protected shallow foundation, which minimizes the depth in which the footings need to be placed. In order to prevent frost heaving, the outside face of the footing is insulated with rigid foam. In colder parts of the country an additional wing of rigid foam would need to be placed perpendicular to the footing. That’s not necessary in the climate of Rhode Island.
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Footing drains are installed and will drain to daylight.
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Protecto Wrap Liquid Waterproofing Membrane is applied to the top of the footing. This is to keep moisture from traveling up through the footings and into the foundation walls—a process sometimes referred to as rising damp. This liquid-applied membrane will help keep the foundation walls dry, which will help prevent the excessive moisture that can build up in the basement and lead to comfort and mold issues.
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Aluminum channel is pinned to the footings and will help keep the Insulated Concrete Forms in position as they’re installed. The particular area in this image will be supporting the front entry of the home, and so the waterproofing membrane is unnecessary.
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The footings are prepped and ready for the next step—installing the ICF blocks.
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The Amvic Plus 3.0 blocks are stacked like Legos. They can be cut with ordinary carpentry tools, making them a viable alternative to formed walls for most builders.
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Rebar is easily integrated into the foundation walls by snapping it into each block’s plastic supports on 8-in. centers.
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Tight fitting blocks can be coerced with a dead blow hammer.
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Nearly complete. When done, the Amvic Plus 3.0 blocks will yield R-30 basement walls.
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Amvic SilveRboard EPS rigid foam is used to insulate the basement slab.
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A gas and vapor barrier is installed over the rigid foam to help keep the basement dry and healthy.
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All of the seams in the gas and vapor barrier will be sealed, including where it transitions to the foundation walls.
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The ICFs are braced and filled with concrete.
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Screed pipes are secured with PVC standoffs to help screed the slab level after the concrete is poured.
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Guertin screeds the slab level.
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Guertin floats the slab.
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A helper precuts sheets of Protecto Universal Primer Free Membrane.
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Guertin precuts the SUPERSEAL dimple mat that will protect the foundation’s waterproofing membrane from damage during backfilling. It will also help keep water away from the foundation walls.
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Before the waterproofing membrane is applied to the outside of the foundation walls, the top of the footing is insulated with Amvic’s SilveRboard EPS foam.
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Protecto Universal Primer Free Membrane is installed vertically along the foundation wall, running from the top of the wall down and over the footing.
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SUPERSEAL dimple foundation membrane is installed over the Protecto Universal Primer Free Membrane. The dimple mat protects the underlying membrane from damage during backfilling and offers an additional layer of protection against water. Once the home’s first floor is framed, the foundation will be backfilled.
View Comments
Nice Job!! only one question, How is the Superseal Dipple fasten to the foundation wall. Did they shoot fastener through insulation to concrete. If so what was the lenght of nails used.
Kind Regards,
Stefan
Good theory, but here's a challenge and would be my only concern: the vapor barrier detailing around the foundation footing.
The contractor has a mix of vapor barriers (ProtectoWrap LWM200 and Universal Primer-Free Membrane outside, what I'm guessing is a polyethylene sheet inside), and vapor retarders (ICF, foam board, concrete, and spray foam).
Where the vertical ICF wall meets the footing on the exterior the contractor has a vapor barrier membrane on the top surface of the footing, and on the outside face of the wall, but the two components don't meet and seal against each other - there is a block of foam held in place with spray foam. So right at the joint there is a higher than 0.00 perm component (a retarder not a barrier). On the inside a similar issue occurs, the liquid membrane barrier on the footing extends inside the ICF wall, but then a foam board is placed over the join and the sheet under-slab barrier is then only "sealed" to the ICF interior wall, which again has a perm above 0.00 (a retarder, not a barrier).
I think if the contractor had installed the first course of ICF and reapplied fluid membrane to couple the footing-top barrier to the inner and outer ICF surfaces, then the subsequent barrier treatments (stick on exterior sheet, and underslab sheet) would be 100% effective as a continuous vapor barrier.
Discus!!
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iris
Stef2011
The Superseal Dimple is fastened to the ICF via the web ties built into the ICF.