Implications of the foundation plan for renovations (Background Report)

LAST MONTH, we received a revised plan from our structural engineering consultant. One crucial aspect was their assessment of the concrete foundation that is needed underneath the basement floor, to support the loads from the structure above. 

The renovation plan, as submitted to the City for review, calls for demolishing the existing walls of the basement men’s room and its adjacent small corridor, in order to install three new strong structural walls atop new concrete footings.

Foundation plan around the basement men’s room

To produce this illustration, I have adapted the engineer’s drawing, by cropping a section and then simplifying the structural elements and adding the blue labels and lines for orientation. 

Below the jump, I interpret the illustration and discuss its implications for synagogue programs.… 

For foundations, the basic structural rule is this: Beneath the existing concrete floor, around all structural walls and posts, there need to be concrete footings that are 2 feet deep. 

Notice that the new footings must extend 1–2 feet into the lower part of the stairwell, and 2 feet into the main corridor. 

In order to do so, both the stairwell’s lower landing and lower course of steps, and the corridor alongside the men’s room and existing storage room, will temporarily need to be turned into a pit.

Furthermore, the plan makes two important assumptions: 

1. There is already a 2-foot-deep footing at the existing north foundation wall, extending out 4 feet.
2. There is already a 2-foot-deep footing at the existing steel post inside the wall between the corridor and the kitchen (next to the kitchen doorway), extending out 3 feet.

Those assumptions will need to be verified before construction begins (by doing test drilling into the floor, here and there). To the extent that the assumptions prove to be incorrect, additional concrete footings will need to be added or extended. (If the post’s footing needs to be extended, that can be done asymmetrically—adding on the corridor side without having to tear up the wall or the kitchen.)

IMPLICATION:  During the demolition and initial construction phases for the new basement restrooms, the stairwell and the corridor will largely be unusable for congregational activities. And that of course affects access to the Social Hall.

This prediction is subject to refinement (and scheduling) after we engage a general contractor for the work.