As Edward J Burrell tells us in Elementary Building Construction and Drawing (1891):
“When common joists are used for spans of more than 9 or 10 feet, there is a want of stiffness, and a tendency for them to turn over sideways. This may be remedied by herringbone strutting.”
A cross section of a herringbone strut system from 1891
Herringbone struts are diagonal members, generally placed in an “X” configuration, that are fastened between joists. By tying one joist to its neighbor, herringbone struts firm up flooring systems. As Burrell alluded to, they also prevent joists from warping or twisting over time.
The joists in the houses on Eager Street stretch 12 feet from pocket to pocket. While this span pales in comparison to some of 16′ wide houses we see in the West side of town, builders nonetheless thought it prudent to include blocking between the joists.
Herringbone struts also made it easier to run pipes and lines because they could be run along the joists without having to drill through solid blocking. In the days of knob and tube electrical wiring, when joists were riddled with holes for wiring, herringbone struts made a lot of sense.
Herringbone struts required an extra degree of craftsmanship, as well. To fix the struts snugly, a beveled cut had to be made on each side of the piece- without the use of a fancy whiz-bang $600 compound miter saw, this was no small task. We’re glad Frank Novak’s crew made the effort, because 107 years after they were laid, our joists are straight as can be without a twist or warp in sight.