The title and subtitles of this post are meant to be puns (albeit bad ones), but if you’ve never heard of a “joist”, they may have struck you as particularly bad spelling errors. So. What is a joist?
First, the etymology: present day “joist” derives from the Old French “giste” which meant “beam supporting a bridge” which derived from the Latin “jacere” which meant “to lie down”.
Still unclear? A joist is a horizontal supporting member that runs between a foundation or walls to support a ceiling and/or floor. Reaching back to our Latin lesson, joists provide support upon which other members may “lie down.” A simple illustration courtesy of the Wikimedia Foundation:
In a typical rowhouse, joists are set into pockets within the brick walls. Not only do they provide support for the floor and ceiling, but they act to stabilize the walls, bringing rigidity to what would otherwise be merely two or three-story towers of brick and mortar. The photo below looks like a super sweet abstract painting, but it also shows the pockets where the joists once sat.
In the photo below, you can see that the joists constitute the main horizontal element of the house- at this point in the deconstruction process, we’re really down to the most basic bones of the building.
Joists represent the largest source of salvageable lumber in a rowhouse. We wanted to harvest all of the rough sawn lumber, but we had to do it in a way that was safe for our workers and ensured that the buildings would retain structural integrity. For the first two houses, we decided to err on the side of caution; we ended up cutting every other joist, leaving around half of the structure to support the century old brick walls. If you look closely in the photo above, you can see that every only every other joist has been removed.
Our process for joist removal was pretty straightforward: we used a Sawzall to cut as close to the pocket as possible, leaving us as much salvageable lumber as could be reasonably harvested. One member of the crew operated the saw, while another firmly held the opposite end of the joist, waiting for it to become free. We then sent the joists through the back of the house where they were sent to…you guessed it…the denailing station.
Cutting the joists gave us a clean view of the end grain- in this case, it looks like most of the joists are loblolly pine and hemlock, two species commonly used for framing lumber during the early 20th century. Once the lumber was denailed, we measured the length, width and thickness to come up with our number of board feet. A board foot is a measure of volume that corresponds to one foot of length x one foot of width x one inch of thickness. Once the wood was measured, we wrote the length of each joist on the end grain, packaged it into bundles, and strapped it together.