A Solid Future: Laying the Foundation for a Green Home
A foundation offers support for the structure, but also the opportunity to include products that contribute to a healthy and comfortable home.
This week, the foundation crew rolled out the blueprints and began assembling the first piece of the home–the footings. Similar to how your feet provide a stable foundation for your body, footings serve as the lowest layer of a home's foundation, distributing the weight of the structure evenly onto the ground.
Home foundations are a requirement in Wisconsin, due to the annual freezing and thawing of the ground caused by the region's harsh winter temperatures. To ensure the stability of a home and prevent shifting, it must be built on undisturbed or engineered soil beneath the frost line, with footers typically located 4 to 6 feet beneath the surface (in southeastern Wisconsin). The frost line represents the depth at which groundwater no longer freezes.
The first day of the foundation process consists of setting up concrete forms for the footings and filling the basement with a few inches of crushed stone.
Form-a-Drain is set up prior to the pouring of footings.
Starting Off on the Right Foot
Form-a-Drain is a 3-in-1 product that acts as the home’s drain tile. Installed on the interior and exterior sides of the footings, it’s a system of perforated pipes that funnel water to the sump crock. In wet areas drain tile is crucial for a foundation, because water around the footings will deteriorate them over time. Form-a-Drain also acts as a concrete form for the footings to be poured.
The system also helps address radon. As an energy-efficient builder, we construct homes that are tightly sealed, amplifying the importance of adequate ventilation. Ventilation is essential for moisture, but also subsoil gas, especially radon.
Form-a-Drain is a component of the “active subsoil gas mitigation system” installed standard in every Tim O’Brien Home. During rough plumbing, after framing, a PVC pipe is inserted into the Form-a-Drain, extended vertically through the exterior walls, and into the attic.
Inside the attic, a fan runs 24/7/365, creating a negative pressure that draws air from below the basement floor like a giant vacuum. The gas passes into the fan, through the roof, and into the atmosphere above. This is called an active mitigation system. Passive systems are also common, but do not include a fan.
Ensuring that our homes are EPA Indoor AirPlus certified, an active system has been a standard of ours for a decade. Installing the system during construction is considerably more convenient, cost-effective, and minimally disruptive compared to the alternative of retrofitting one on the exterior at a later date.
The foundation crew pours concrete onto a conveyor truck to create the footings.
Built to Last
Once the foundation wall formwork is assembled, an intricate lattice of rebar is installed between the forms, and concrete is poured with multiple mixer trucks and a conveyor truck.
After 24 hours, when the concrete has cured to about 16% of its total strength, the forms are removed and rebound for extraction by a transport truck with an articulating crane. Within a few days of pouring the walls, the conveyor truck returns once more, but this time with stone, to bury the exterior Form-a-Drain in 12 inches of stone.
A thick layer of crushed stone prevents the perforated tubing from becoming clogged with soil. After 7 to 10 days, the walls are backfilled with dirt. The concrete continues to cure for a total of 28 days to achieve its 4000 PSI strength rating.
Concrete recently poured into the foundation wall forms.
Another product included within our homes is a drainage mat on the outside of basement walls. Delta-MS, the waterproofing membrane, is a hardened, dimpled plastic that creates an air gap between the foundation wall and soil.
The drainage mat is installed at the perimeter, except where stone borders the basement walls in the stoop and garage. An air gap allows water to freely drain down the exterior of the basement walls into the Form-a-Drain, ensuring that the walls remain dry. The sump crock collects water from the Form-a-Drain system and pumps the water onto the yard.
To keep the basement at a similar temperature to the home, the interior of basement walls are wrapped with 1-1/2 inches of rigid foam. Furthermore, spray foam is applied during the insulation process to the box sills in the basement–where the framing rests on the foundation. This section of the building envelope is the thinnest and most vulnerable to heat loss and moisture intrusion.
The foundation wall drainage mat is the brown and orange sheet. Rigid foam insulation is installed with taped seams on the inside of the basement walls.
The basement is conditioned and regulated similar to the first and second floors. Vents are installed in the basement duct mains to supply conditioned air. Encouraging air circulation in the basement deters moisture accumulation and stagnant air, two predecessors of a problem basement.
Installing insulation and providing air flow to the basement reduces energy costs, strain on the mechanical equipment, increases comfortability and fortifies the structural integrity of the home.
A sneak peak of framing from above.
The excavator will return to backfill dirt around the foundation and deposit stone into the garage and stoop. In the same breath, the plumber will install water and sewer connections. Pipes, installed 9 feet below the front yard, connect the home to the municipal mains below the road, providing a supply of fresh water and waste disposal.
Between backfill and framing, enough wood to make a beaver blush will be delivered into the driveway. Smelling the scent of fresh lumber from miles away, the framers will embark on a caffeine-induced odyssey, armed with multiple t-shirts and an unwavering determination to hammer life’s frustrations into thousands of nails.