Once driven to resistance, each pile was precisely cut to a predetermined height above the bottom of the grade beams. Instead of pile caps, grade beams will continuously carry the load between each of the piles. Each pile has a steel saddle that allows the concrete beams to connect mechanically to the pile — if you were to pour concrete directly onto a wood pile, there’s nothing to connect them long term.
Next it was time for concrete forming. Grade beams only work if they are properly bridging the space between the piles and piers to carry the load of the house. This means a ton of reinforced rebar steel and concrete. The survey company once again visited the site to dimension each of the grade beams properly by pinning the outside of the footings before concrete was poured. With sustainability in mind, the concrete spec in this case was for lower embodied carbon concrete.
Though grade beams and footings are essentially the same thing, grade beams are typically used in commercial construction while footings are typically residential. The Cape Cod Hemp House is a bit atypical in that it’s foundation structure utilizes grade beams throughout due to both the complexity of the structure and its use of piles. At the Cape Cod Hemp House, grade beams are used in areas that are not ultimately load-bearing to ensure the longevity of the house.
As with most aspects of the Cape Cod Hemp House, sustainability and a low carbon footprint were at the forefront of the owner’s minds.
This led the team to use lower-embodied carbon concrete, which contains a higher percentage of fly ash than standard Portland cement ... this did not come at a higher price point, and was a simple swap in the building specifications.
Most houses require two to four footings which transfer the load of the house directly to the ground. Since this house sits atop its piles, the grade beams at the Cape Cod Hemp House are oversized. They are 18” thick and 30” wide, and are full of reinforcing steel to ensure that they are strong enough to hold up the house. Each grade beam also has turned up reinforcing steel which was tied into a new tectonic structure in this building — the pier.
Roughly 28 piers, or vertical concrete columns, sit atop the grade beams. Everywhere there’s a pier, reinforcing steel is tied into the grade beam cages. The location and elevation of these piers are precisely planned as there is only 1”-2” of forgiveness in the building plan allowing construction to stay within code for the zoned building height.
As with most aspects of the Cape Cod Hemp House, sustainability and a low carbon footprint were at the forefront of the owner’s minds. This led the team to use lower-embodied carbon concrete, which contains a higher percentage of fly ash than standard Portland cement. Fly ash is said to improve the strength and segregation of the concrete and makes it easier to pump. Ultimately this did not come at a higher price point, and was a simple swap in the building specifications.
