The aforementioned piers were precisely poured at specific elevations, and are what holds up the house, but they were also the first step in enclosing the basement at the Cape Cod Hemp House. Though there are no current storm surge engineering requirements, per the owners’ request the basement walls needed to meet future potential flood restrictions because of rising sea levels and an increase in catastrophic weather-related events. Because this means the basement at the Cape Cod Hemp House was ultimately built to withstand lateral force conditions, CMUs (concrete masonry units) were used to infill between the piers. These serve only to keep sand from flowing into the basement under normal conditions, and will blow out in the case of an extreme event.
Before the CMUs were installed, however, the crew installed interior footing drains and radon piping followed by an Aero Aggregate. Here the team hit another small snag: the drainage piping specified was perforated 4” diameter “ADS” corrugated high density polyethylene for its lower carbon footprint, but in an attempt to use a superior product, the site contractor mistakenly installed better-performing schedule 40 PVC pipe as they would typically use on a high-end project such as the Cape Cod Hemp House — without understanding the reasoning behind the specified product. All piping was done and the Aero Aggregate laid before the mistake was noticed. Ultimately, the carbon impact of removing the aggregate and piping, and redoing it with the correct products was much higher than leaving it as-is, so the team made the call to leave it.
All piping was done and the Aero Aggregate laid before the mistake was noticed.
Ultimately, the carbon impact of removing the aggregate and piping, and redoing it with the correct products was much higher than leaving it as-is, so the team made the call to leave it.
To create a secure sub-slab surface within the interior of the basement, the crew installed and compacted a layer of Aero Aggregate. Made from 100% post-consumer recycled glass, the Aero Aggregate was used beneath the slab inside the basement, and will also be used as an exterior insulation below grade. Once compacted, the crew laid reclaimed 1” XPS insulation to decrease overall energy loss through the slab. Like the other concrete elements, the slab was then poured with lower embodied carbon concrete.
A bituminous water-stop was installed between the grade beams and CMUs, though the team is aware that this may have been an oversight. Technically a water-stop should occur at each of the innumerable cold joints between each of the CMUs, as a CMU wall and a concrete wall are not the same in their points of weakness. Live and learn, and best of intentions. A spray applied, petroleum-based waterproofing was also applied to the exterior of the CMU walls. Though the owners wished to limit or eliminate the use of oil-based products, this was a necessary choice, and one that came with stringent specifications from the architects. Following this waterproofing, drainage boards were placed against the walls to create a vertical airspace between the soil/sand around the foundation and the waterproofing on it’s exterior. This allows for any water migrating horizontally to drop down the wall into the footing drain rather than come in contact with the house. All this said, there currently is no hydrostatic pressure from the water table at this site. Infill below grade is all sand; with the various waterproofing measures taken, the lack of water-stop throughout the CMU walls should not create any issues for the Cape Cod Hemp House.
To round out the month, the local utility company installed a temporary electrical panel to power the site and crew trailer. The project also received their foundation inspection sign-off from the town. In a normal build, the building inspector would examine the “bottom of foundation or form” prior to concrete placement, but in the case of the Cape Cod Hemp House, the inspector relied on the inspection affidavits from Structures Workshop and the coastal engineers to ensure that everything in the foundation met the requirements in the drawings.
