Concrete must be used and must have a minimum compressive strength of 3,000 pounds per square inch.
Footing size and thickness must be in accordance with Table 1. (See sections 4 and 5 for determining post spacing and joist length.)
Post attachments must be in accordance with Figure 1 except expansion anchors are also permitted – and any instructions from the manufacturer of the anchor must be followed.
Post anchors must include a 1-inch-minimum base plate. Steel plates are not required.
Each post must bear directly over the middle one-third of a footing.
Footings must bear on solid ground below the frost penetration level or at least 48 inches below finished grade, whichever is deeper. Bearing onto unprepared fill material, organic soil, alluvial soil, or mud is prohibited. The bearing capacity of the soil is presumed to be at least 2000 pounds per square foot (psf), and must be verified by a building inspector prior to placement of concrete.
If the edge of a deck footing is closer than 5 feet to an existing house wall, the footing must bear at the same elevation as the existing footing for that wall.
Construction of footings over utility lines or any service pipe is prohibited.
Note: Call the utility provider before digging.
SECTION 3: POSTS AND POST-TO-BEAM CONNECTIONS
Posts must comply with all of the following:
The post height, measured from the top of the footing to the underside of the beam, must be in accordance with Table 2.
2. Any post supporting a beam splice must be a minimum of 6”x6”.
3. Beams must be attached to posts by the appropriate methods shown in Figure 2. Toe-nailing of beams to posts is prohibited.
4. Post caps, as shown in Figure 2, must be specifically designed for 2- or 3-ply beams and the post size used. Attachment must be in accordance with the manufacturer's instructions.
5. It is recommended that cut-ends of posts should be field-treated with a wood preservative. These preservatives can be found in the paint department of most hardware or home-center stores.
SECTION 4: BEAMS
Beams must comply with all of the following:
As shown in Figure 3, the beam-span length is measured between the centerlines of 2 adjacent posts and does not include the overhangs.
2. Beam size is determined using Table 3A or 3B. The depth of flush beams must be greater than or equal to the joist depth.
3. Beams may overhang past the center of the post up to one-fourth of the actual beam span, as shown in Figure 3.
4. Where multiple 2x members are used to assemble a beam, the plies of the beam must be fastened in accordance with Figure 4.
5. Pressure-preservative-treated glulam beams are permissible for spans longer than those shown in Table 3. However, a design and plan submission is required during the permit application process.
MAXIMUM BEAM-SPAN LENGTH1
FOR DOUGLAS FIR/LARCH
, SPRUCE/PINE/FIR (SPF)3
, WESTERN CEDAR, PONDEROSA PINE4
, AND RED PINE4
- See PDF for table - See PDF for table
SECTION 5: JOISTS
Joists must comply with all of the following:
The joist-span length is measured between the centerline of bearing at each joist-span end and does not include the overhangs. Use Table 4 to determine the joist size based on span length and joist spacing. See section 12.4 for limits on joist spacing if the decking consists of a wood-plastic composite.
2. See Figures 5 through 7 for joist-span types.
3. Joists must bear at least 3 inches nominal onto beams, unless joist hangers are used in accordance with section 7.
4. Joists may overhang past the center of the beam up to one-fourth of the actual joist span.
5. Provide full-depth 2x blocking or bridging for 2”x10” or deeper joists at intervals not exceeding 8 feet – except the blocking can be reduced to 60% of the height if placed above a beam, for drainage purposes. Attach the blocking or bridging with (3)10d toe-nails at each end.
6. Attach a continuous rim joist as shown in Figures 5 and 7 unless blocking or bridging is provided for each joist at the beam where a joist overhang begins. Attach the rim joist to the end of each joist with (3)10d nails or (3)#10 by 3-inch wood screws.
JOISTS WITH DROPPED BEAM – DECK ATTACHED AT HOUSE
JOISTS WITH FLUSH BEAM – DECK ATTACHED AT HOUSE
(See section 10 for more information.)
SECTION 6: JOIST - TO - BEAM CONNECTIONS
Joists must be attached to beams in accordance with Figure 8 and all of the following:
Use Options 1 or 2 if joists bear on a dropped beam.
2. Use Option 3 if joists bear at a flush beam; see section 7 for hanger requirements.
3. Mechanical fasteners or hurricane clips must have a minimum capacity of 100 pounds in both uplift and lateral directions. Installation must be in accordance with the manufacturer's instructions.