GUARD POST TO END JOIST
Figure 26
GUARD POST TO RIM JOIST
SECTION 14: STAIRS
Stair dimensions. Stair dimensions must comply with all of the following:
1.
The minimum width of a stairway is 36 inches.
2.
Handrails and associated trim may project a maximum of 4 1/2 inches into the required width at each side of the stairway. The minimum clear width at and below the handrail, including at treads and landings, cannot be less than 31 1/2 inches where a handrail is installed on one side, and 27 inches where handrails are provided on both sides.
3.
Stair geometry and openings must be as shown in Figure 27.
Figure 27
TREADS AND RISERS
4.
Within a stairway flight, the largest tread depth may not exceed the smallest tread depth by more than 3/8 inch, and the largest riser height may not exceed the smallest riser height by more than 3/8 inch.
5. If the total vertical height of a stairway exceeds 12 feet, an intermediate landing is required and must be constructed as a free-standing deck with flush beams and with posts.
6. Any landing width must equal or exceed the total width of the stairway it serves.
Stair stringers. Stringers must comply with all of the following:
1.
Stringers must be sawn or solid 2”x12”s complying with the above tread and riser dimensions.
2. Cut stringers must be spaced no more than 18 inches on center.
3. Stringers must bear on a solid surface, a minimum of 3 1/2 inches thick and 8 inches in diameter, and attach to the deck or a landing in accordance with Figure 28. Prior to placement of solid surface, all loose or organic material shall be removed.
4. Stringer-span length is measured using the horizontally projected distance between the centerlines of bearing at each end.
5. The span length of a cut stringer must not exceed 6 feet-0 inches, and the throat size of cut stringers must not be less than 5 inches, as shown in Figure 29.
Solid-stringer exception: Stringers for a stairway that has a width of 36 inches may have a horizontally projected span of up to 13 feet 3 inches if the stairway is framed solely with 2 solid stringers.
Intermediate-supported stringers: If the total stringer length exceeds the above dimensions, a 4”x4” post may be provided to support the stringer and shorten its span length. The 4”x4” post must be notched and bolted to the stringer in accordance with Figure 2. The post must bear over the middle one-third of a footing that is constructed in accordance with Figure 29 and must be attached as shown in Figure 2. An intermediate landing as described above may also be provided to shorten the stringer span.
Figure 28
STRINGER BEARING
LOWER BEARING AT FOOTING LOWER BEARING AT FOOTING – FROST PROTECTED
Figure 29
STRINGER BEARING
Figure 30
Tread and riser material. Treads and risers must comply with all of the following:
1.
Tread material must be equivalent to the decking specified in section 12 and be attached in accordance with Figure 31, except wood-plastic composites must be attached in accordance with the manufacturer's instructions.
2.
Stairs constructed using the solid-stringer exception noted above must have treads constructed of 2x wood material only and be attached in accordance with Figure 30.
3.
Risers that are not open (as shown in Figure 27) must be framed with 1x lumber minimum or an manufacturer recommended wood-plastic composite.
Figure 31
STAIRWAY TREADS
Table 7
1 Assumes 300 lb concentrated load, L/288 deflection limit, No. 2 grade, and wet service conditions.
2 Incising assumed for refractory species including Douglas fir-larch, hem-fir, and spruce-pine-fir.
3 Design values based on northern species with no incising assumed.
Stair guards. Guards must be provided on all open sides of stairs consisting of more than 3 risers. Stair guards must comply with section 13 and Figure 32.
Figure 32
STAIR GUARDS
Stair handrails. A flight of stairs with more than 3 risers must have at least one handrail that complies with all of the following:
1.
The handrail must be located at least 30 inches, but no more than 38 inches above the nosing of the treads – except that a volute, turnout, starting easing, or transition fitting may depart from these dimensions. Measurement must be taken from the nosing to the top of the rail.
2.
The handrail must be attached to a stair guard or exterior wall acting as a barrier as shown in Figure 33.
3.
The handrail and connecting hardware must be decay- and corrosion-resistant.
4.
The handrail must have a smooth surface with no sharp corners and must be graspable, as shown in Figure 34. Recessed sections may be shaped from a 2”x6” or five-quarter board, as shown there.
5.
Handrails must run continuously from a point directly over the lowest riser to a point directly over the highest riser.
6.
Handrails may be interrupted by guard posts.
Figure 33
Figure 34
Spiral stairs. Stair dimensions above are for standard stairs secured in accordance with methods shown in this appendix. Spiral stairs are allowed at decks when designed in accordance with the provisions of Chapter SPS 321.04. Connection of spiral stairs to decks and the supporting load path shall be designed in accordance with accepted engineering practices and with applicable provisions of the Uniform Dwelling Code.
SECTION 15: FRAMING PLAN
A typical framing plan shows a bird's-eye or plan view of the joist and beam layout; the location of the ledger board, diagonal bracing or hold-down devices, posts, and footings; and the type, size, and spacing of the ledger board fasteners. You can use the sample typical deck framing plan shown on the next page in combination with the requirements in this document to complete your deck.
Figure 35
TYPICAL DECK FRAMING PLAN
Decking: ⍽ 2x4
⍽ 2x6 ⍽ five-quarter board ⍽ wood-plastic composite (per ASTM D 7032)
⍽ Other decking, evaluation report number:
Joists: size: ⍽ 2x6
⍽ 2x8 ⍽ 2x10 ⍽ 2x12 spacing: ⍽ 12 in. ⍽ 16 in.
⍽ 24 in.
joist span dimension: ft. -
in.
overhang: ⍽ Yes ⍽ No overhang dimension: ft. - in.
rim joist: ⍽ 2x6 ⍽ 2x8
⍽ 2x10 ⍽ 2x12
Beam(s): number of plies: ⍽ 2 ⍽ 3 size: ⍽ 2x6 ⍽ 2x8 ⍽ 2x10 ⍽ 2x12
overhang: ⍽ Yes ⍽ No overhang dimension: ft. - in.
Posts: size: ⍽ 4x4
⍽ 4x6 ⍽ 6x6 height:
ft. - in.
Footings: size: in.
⍽ square ⍽ round thickness: in.
Ledger: ledger board size: ⍽ 2x8 ⍽ 2x10 ⍽ 2x12 ⍽ Not applicable (free-standing deck)
fastener: ⍽ Through bolt ⍽ Lag screw ⍽ Wood screw
⍽ Expansion anchor ⍽ Adhesive anchor
Lateral support: ⍽ Tension-tie
⍽ Diagonal bracing, size: ⍽ 2x
(not permitted for free-standing deck)