Email #23 - Sleeper Boards, Not Joists

I'm sure sending out a lot of emails. Hope you don't mind. Maybe I should change my name to "SPAMets."

Anyhow, this email is in response to a question by M. Arch. student Eric Henyey. From looking at the photo in email #21 he asked:

"What is the floor structure?... It looks like wood joists with some sort of decking between each pair of joists."

Attached is a more detailed view of the historic floor structure, as seen from both sides. The top color view is at the base of the grand stairs on the first floor. What look like wooden joists here are not; instead they are the historic "sleeper boards” used for leveling the floors, according to Steve Brown, project superintendent  for Mortenson.

Steve explained the floor structure of the 1st and 2nd floors like this: the basic structure is a six-inch slab of concrete reinforced with steel rebar. In the bottom b&w photo, you can see a piece of this rebar where a small hole was drilled through the 1st floor ceiling. Note the board formwork pattern in the concrete.

To install the finished floor above the concrete slab back in 1908, they first installed non-structural sleeper boards about 2.25" wide and 3" deep. Then they poured in grout (not concrete) and while still wet, they could accurately level the sleeper boards. Grout flowed under the sleeper boards too. When all was leveled, set and done, they installed the finished flooring atop the level sleeper boards. Cool.

Thanks, Steve Brown.

John Stamets
Aug. 23, 2006

See also #26 and #28