Design For Deconstruction - US Environmental Protection Agency

OVERVIEW DESIGN FOR DISASSEMBLY
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The 600 s.f. classrooms are 20’ x 30’ in dimension,
and the structural framing would typically span the short
direction. As noted above, however, there was a desire to
keep the walls between classrooms non-structural so the
classroom layout could be changed in the future. To span
the 30’ dimension would require either trusses to span
the full length, or roof joists with a beam at the midpoint
to reduce the span. The trusses can be designed to carry
much higher loads, with fewer members and connections,
so these were selected as the framing (see figure 5.8). With
24” o.c. wall framing, the roof framing is required to align
with the studs since the top plates span too far to transfer
the truss loads to the studs. This works well with the
modular design of the school, and the trusses were spaced
at 48” o.c.
Figure 5.8
The uplift forces on a roof can be quite large, so metal
straps or hurricane clips are used to tie the roof structure
to the walls. With fewer, larger members, in this case it
required a 24 inch long strap secured with two lag bolts
and 24-10d nails. This hardware again produces a very
strong connection, but one that is difficult to disassemble.
By working with the truss manufacturer, this connection
was simplified to use two through bolts and a much smaller
8” strap to connect the top plates to the studs.