Georgia-Pacific APA Engineered Wood Construction Guide - Roofs - Manual (Page 6)

ENGINEERED WOOD CONSTRUCTION GUIDE ■ FORM NO. E30V ■ © 2011 APA – THE ENGINEERED WOOD ASSOCIATION ■ WWW.APAWOOD.ORG 63
Roof Construction
from Table 30, and minimum fastener requirements are given in Table 32 . Increased nail sched ules may be required in
high wind zones. Recom mended nail schedules for high wind zones are described in APA Data File: Roof Sheath ing Fastening
Schedules for Wind Uplift, Form T325 .
APA RATED SHEATHING is equally effective under built-up roofing, asphalt or fiberglass shingles, tile roofing, or wood
shingles or shakes. Roof trusses spaced 24 inches on center are widely recognized as the most economical construc-
tion for residential roofs. However, using fewer supports with thicker panels – e.g., Performance Category 23/32 or 3/4
panels with a span rating of 48/24 over framing 48 inches on center – is also cost effective for long-span flat or pitched
roofs. Recommended live loads are given in
Table 30 . Nailing recommendations are given in Table 32 .
When support spacing exceeds the maximum length of
an unsupported edge (
see Table 30 ), provide adequate
blocking, tongue-and-groove edges, or other edge sup-
port such as panel clips. Some types of panel clips, in
addition to edge support, automatically assure proper
panel spacing. When required, use one panel clip per
span, except use two clips for 48-inch or longer spans.
See APA’s Build A Better Home: Roofs, Form A535 , for
additional recommended details to prevent moisture infiltration in roofs.
Preframed Roof Panels
Spans of 8 to 12 feet are usually the most practical with preframed panel construc tion, although spans to 30 feet are
not uncommon. APA panels with stiffeners preframed at 16 or 24 inches on center (Figure 22) are common. The long
dimension or strength axis of the panel typically runs parallel to supports. Stiff eners and roof purlins provide support
for all panel edges. Minimum nailing requirements for preframed panels are the same as for roof sheathing.
In preframed panels 8x8 feet or larger (Figure 23), the panel strength axis may run either parallel or perpendicular to
stiffeners spaced 16 or 24 inches on center. Stiff eners and roof purlins provide support for all panel edges. Recommenda-
tions in
Table 33 are based on long dimen sion or strength axis of the panel parallel to supports. Deflection limits are
1/180 of the span for total load; 1/240 for live load only. See Table 34 for design information on stiffeners for preframed
panels. Nailing requirements for preframed panels are the same as for roof sheathing.
Main supporting
glulam member
FIGURE 22
PREFRAMED ROOF PANEL
(4' x 8' – APA Structural Panels
Strength Axis Parallel to Supports)
Metal purlin hanger
Roof purlin
8' o.c. (typical)
APA structural panel
Stiffeners16" o.c.
or 24" o.c.
Stiffeners of
adjacent preframed panel
Metal joist
hangers
Strength axis
Metal purlin hanger Main supporting
glulam member
Glulam purlin
APA structural panel
Stiffeners
16" or 24" o.c.
Metal joist
hangers
FIGURE 23
PREFRAMED ROOF PANEL
(8' x 8' or larger – APA Structural Panels
Strength Axis Perpendicular to Supports)
Strength axis
Glulam purlin
Panel clips or other
edge support if
required, or single
large-sized panels