REVIEWED BLD BLD2024-0900+Calculations+7.2.2024_2.46.28_PM+4356031BLD2024-0900
RECEIVED
Jul 11 2024
To whom it may concern,
REVIEWED
BY
CITY OF EDMONDS
'• BUILDING DEPARTMENT::
..............................................:
Attached are the span charts that were obtained via Washington State Building Code IRC
2021 as the operative prescriptive deck building guidelines and how they are applicable to
our deck project for Cordell Hauglie .
In our plans attached we are building this deck using 2x8 douglas fir joists with a maximum
span on this deck of 8' from the house to the beam. The span chart below indicates using
2x8 joists we can span up to 9'5" with 16" spacing. See Below:
TABLE R507.6
MAXIMUM DECK JOIST SPANS
LOAD'
(Psf)
JOIST
SPECIESb
IOIST
SIZE
ALLOWABLE JOIST
SPANb•c
(feet -inches)
MAXIMUM CANTILEVER0
(feet -inches)
Joist Spacing
(Inches)
Adjacent Joist Back Spang
(feet)
12
16
24
4
6
1 8
1 10
12
14
16
18
60 Live
Load or
70
Ground
Snow
Douglas fir-
Iarche,Hern-
fire,
Spruce -pine.
fir,•
2x6
7-11
7-1
5-9
1-0
1-6
NP
NP
NP
NP
NP
NP
2x8
10-5
9-5
7-8
1-0
1-6
2-0
2-1
NP
NP
NP
NP
2x10
13-3
11-6
9-5
1-0
1-6
2-0
2-6
2-8
NP
NP
NP
2x12
15-5
13-4
10-11
1-0
1-6
2-0
2-6
3-0
3-3
NP
NP
Load
Redwood,
Western
Cedarsf,
Ponderosa
Pinef
Red Pinef
2x6
7-4
6-8
5-10
1-0
1-4
NP
NP
NP
NP
NP
NP
2x8
98
8-10
7-41-0
1-6
1-11
NP
NP
NP
NP
NP
2x10
12-4
11-0
9-0
1-0
1-6
2-0
2-6
2.6
NP
MVP
NP
2x12
14-9
12-9
10-5
1-0
1-6
2-0
2-6
3-0
3-0
NP
NP
Next, the spacing between the deck posts has a max span of 8'3-1/4" between posts as
currently proposed. Using the IRC charts we have confirmed the maximum allowable span
for a 4x12 beam is 8'6" when the effective deck joist span is 8' or below. The tributary area
of each side deck post is under 27 sq ft so we have used the column in the chart for the
40sq ft tributary area. The tributary area for the middle deck post is under 43 sq ft so we
have used the column in the chart for 60 sq ft tributary area. See below:
TABLE R507.5
MAXIMUM DECK BEAM SPAN - 60 PSF LIVE LOAD or
70 PSF GROUND SNOW LOADc
BEAM SPECIESd
BEAM SIZEe
EFFECTIVE DECK JOIST SPAN LENGTHa•'
(mot)
6 8 10 12 14
161 18
MAXIMUM DECK BEAM SPAN LENGTHa
(feet -inches)
Douglasfir-larchg,
Hem -firs,
Spruce-pine-firg
1-2x6
3-5
2-10
2-5
2-2
2-0
1-10
1-9
1-2x8
4-7
3-8
3-2
2-10
2-7
2-5
2-4
1-2x10
5-8
4-9
4-1
3-8
3-4
3-1
2-11
1-2x12
6-7
5-8
5-0
4-6
4-1
3-10
3-7
2-2x6
5-2
4-6
4-0
1 3-5
3-1
2-10
2-7
2-2x8
6-11
6-0
5-3
4-7
4-1
3.8
3-5
2-2x10
8-5
7.4
6-6
5-10
5-2
4-9
4-5
2-2x12
9-10
8-6
7-7
6-11
6-4
5-9
5.4
3-2x6
6-6
5-7
5-0
4-7
4-2
3-9
3-5
3-2x8
8 8
7-6
6-8
6-1
-6
5-0
4-7
3-2x10
10 7
9-2
8-2
7-6
L6-111
6-4
s-10
3.2x12
12-4
10-8
9-7
8-9
8-1
7-7
7-1
Deck Footings:
For the corner posts, using a tributary area of 40 (the proposed project has a tributary area
of 26.25) the proper deck footing size is 16" diameter and 6" thick. Our proposed project
specs are adequate at 16" wide and 18" deep. For the middle post, using a tributary area of
60 (the proposed project has a tributary area of 42.5) the proper deck footing size is 19"
diameter and 6" thick. Our proposal project specs are adequate at 19" wide and 18"deep.
LNE OR
GROUND
SNOW
LOAD•
(P�
40
TABLE R507.7.1
MINIMUM FOOTING SIZE FOR DECKS
- _
TRIBUTARY
LOAD -BEARING VALUE OF SOILS••• (psn
1,600'
2,000
AREA
IRS)
Skis of a
sausne
footing
(inches)
Dksnwta of s
in Irounnch
g ( I
Thlcknsss
(Inches(foot-'
Slds of
sewn
fooling
(Inches)
DlsmNsr of ■
round foot.
Ing (Inches)
Tltltknrss
(YfehesN
a
f
5
,
8
6
7
6
6
20
40
10
14
2
6
9
9
6
16 J
6
12
14
6
60
17
19
6
15
17
6
K0
20
22
7
17
19
6
100
22
25
8
19
21
6
120
24
27
9
21
23
7
140
26
29
10
22
25
S
160
28
31
II
24
27
9
j
Deck post height:
Using a tributary area of 60 again, (proposed deck has a maximum tributary area of 42.5)
the maximum deck post height for a 4x4 in Douglas Fir is 87". Our proposed deck post
height is 8'tall. See below:
TABLE R507.4
DECK POST HEIGHT
LOADSb
(Psf)
POST SPECIESC
POST SIZEd
TRIBUTARY AR (sq. ft.)
20 40 1 60 1 80 1 100 120 1 140 1 160
MAXIMUM DECK POST HEIGHTa (feet -inches)
60 Live
Load,
s60 Ground
Snow Load
Douglas Fire, Hem-
fire, SPFe
4 x 4
14-0
10-10
8-7
7-0
5-8
41
NP
NP
4 x 6
14-0
13-10
11-1
9.5
8-2
7-3
6.4
5-4
6 x 6
14-0
14-0
14-0
14-0
14-0
13-3
10-9
6-11
8x8
140
140
140
140
140
140
140
14-0
Redwood , Western
Cedars', Ponderosa
Pine', Red Pine'
4 x 4
14-0
10-3
7-0
NP
NP
NP
NP
NP
4x 6
14-0
13-6
10-6
8-4
5-10
NP
NP
NP
6x 6
14-0
140
1 140
1 140
1 11-11
NP
NP
NP
8x8
14-0
140
1 140
1 140
1 14-0
14-0
140
1 14-0
Ledger Connection:
Using a joist span of 8' the IRC states the on center spacing of lag screws to be at no more
than 23" apart. Our lag screws will have 2 for each 16" joist bay. See chart below:
FLOORS
TABLE R107.9.1.30)
DECK (EDGER CONNECTION TO BANG JOIST
LOADo (PM JOIST SPAN. ON'CEgTER SPACING OF FASTEMERS• (Inch")
(feet) 4,4nah dimmier `o sc. ow we YYlnch dlsmoger boll w4lh '1 :hlClt d•
'114"ch M"Wtxn •MaIhkV4. '/,.Inch mo=Imum •hNthbW 14"Ch "WE
6 30 36
p 23 36
10 18 34
40 five load 12 I5 29
E14 13 24
16 11 21
18 10 .