Installation Guide

Floor Construction
ENGINEERED WOOD CONSTRUCTION GUIDE
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FORM NO. E30V
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© 2011 APA – THE ENGINEERED WOOD ASSOCIATION
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WWW.APAWOOD.ORG
43
APA Panel Stair Treads and Risers
A growing number of builders and manu facturers are using APA pan-
els for treads and risers of both site-fabricated and prefabricated stairs
in closed-riser stair ways. Risers support the front and back of the tread,
creating a very short effective span.
APA panel stair treads may be used interchangeably with boards when
the system is to include closed risers. Maximum span between string-
ers is 42 inches (check local code require ments). Rounded nosing may
be machined into the tread, but should be covered by a finish flooring
material such as carpet and pad in order to prevent excessive wear or
damage to veneers exposed by rounding. Risers may be any available
APA panel grade with a Performance Category of at least 19/32. Panel
grade and Performance Category
recommendations for the treads
are given in Table 16. Glue is rec-
ommended to improve stiffness
of connections and to eliminate
squeaks. Apply con struc tion
adhesive meeting ASTM D3498
or APA Performance Specification
AFG-01 to all joints, with partic-
ular attention to the connection
at the back riser. Regard less of
where glue is used, nail all edges
of treads as indicated in Figure 7.
Detail A is the simplest system, but
Detail B is preferred since it elimi-
nates end-grain nailing at the back
riser and may be used for all rec-
ommended panels.
Heavy Duty Plywood Floors
Above-grade plywood floors may
be designed to support forklift
trucks in areas of heavy loading
or to support rela tively high loads
imposed by ware house shelving or
stacked storage. Heavy-duty plywood floors also make excellent mezza nine decks and vibra tion-resistant surfaces for
mounting computer equipment.
Tables 17 and 18 give plywood recom mendations for uniform and concen trated (e.g., forklift traffic) loads. These assume
the use of plywood continuous over two or more spans with face grain across supports. Structural edge support
must be provided where high concen trated loads occur. Where no lift-truck use is expected, 2-inch wood framing
is adequate.
In addition to providing structural strength, a wearing surface should be provided to resist crushing wood cells and
avoid abrasion whenever an indus trial floor is subject to hard wheel or caster traffic. An expendable layer of ply wood or
a dense wear surface, such as tempered hardboard, should be used if wheels are small, hard or heavily loaded.
TABLE 16
APA PANEL STAIR TREADS
Panel Grade
(a)
Minimum
Performance Category
Nail-
Glued
Nailed-
Only
APA RATED
STURD-I-FLOOR 19/32 23/32
(a) Other appropriate APA panel grades may be
substituted for Sturd-I-Floor, providing mini-
mum thickness complies with recommenda-
tions above.
3/8"
min.
1 1/2”
3 1/2”
1 1/8”
Finish
flooring
material
19/32 minimum
Performance Category
APA panel riser (any grade)
Stringer
8d common nails 6" o.c.
(a)(b)
8d common nails 12" o.c.
(a)(b)
Along leading edge add two
nails at each end.
APA panel tread
(strength axis
either direction)
FIGURE 7
APA PANEL STAIR TREADS AND RISERS
(a) Predrill tread end grain at mid-thickness with 3/32" bit. Maintain at least 3/8" edge distance in riser.
(b) See Table 5, page 14, for nail dimensions.
Tread
Detail B (Preferred)
Detail A (May be used for
plywood treads and 1-1/8
Performance Category
composite panel or OSB
treads)
Riser
Riser
Tread
Lumber block