Installation Guide

3
Building Decks
Joist/
Beam
Depth
Joists
1. Locate your deck’s joist span in the table
below; this will determine your joist size and
spacing.
Joist Size
2x6 2x8 2x10 2x12
12" up to 9' 9-12' 12'-16' 16'-19'
16" up to 9' 9'-12' 12'-14' 14'-18'
24" up to 8' 8-10' 10'-13' 13'-16'
Note: All 5/4" decking must use 12" joist spacing.
Joist size: by
Joist spacing: in.
2. Now, use the equation below to determine
how many interior and side joists you will
need.
For 16" joist spacing:
(deck length X .75) + 1 = joists
For 24" joist spacing:
(deck length X .5) + 1 = joists
3. The lengths of your joists will be as follows:
Interior joist length: deck width - 3" =
Side joist length: deck width - 1
1
/2"=
4. You will also need one ribbon joist.
Ribbon joist length
(same as deck length): =
Joist
Spacing
Joist Size
2x6 2x8 2x10 2x12
Single Beam 4x6 4x8 4x10 4x12
Double Beam (2) 2x6 (2) 2x8 (2) 2x10 (2) 2x12
Cantilever 1.00' 1.33' 1.67' 2.00'
Beam size: by
#of boards:
Maximum cantilever : = ft.
2. Beam length (same as deck length):= ft.
3. Now use the table below to determine your
maximum allowable beam span.
Deck Width
6' 7'-8' 9'-10' 11'-12' 13'-14' 15'-16' 17'-19'
6" 6.5 6
8" 8.5 7.5 7 6
10" 10 9 8 7.5 6.5 6
12" 11.5 10 9.5 8.5 8 7.5 7
Maximum beam span: = in.
Posts
1. First, use the equation below to determine
how many posts you will need. Note: If your
deck will have more than one beam, multiply
the total below by the number of beams.
# of posts:
[(deck length - 2 x cantilever)
÷ beam span] + 1 = posts
2. Then, use the equation below to determine
your post spacing.
Beams
1. Decide whether you will be using a single
or double beam (see Attach the Beam on page
6 for details). Then use the following table to
determine the beam size, the number of
boards per beam (in parentheses) and the
maximum allowable cantilever.
Ledger
Decking
Interior joist
Side joist
Beam
Ribbon joist
Post
BEAM SPAN
▲
▲
JOIST
SPACING
▲
▲
JOIST SPAN
DECK WIDTH
▲
▲
▲
▲
JOIST
CANTILEVER
▲
▲
DECK LENGTH
▲
▲
DECK HEIGHT
▲
▲
3