3 The thickness of the sheathing over the band board must not exceed 15/32”.
4 The maximum gap between the face of the ledger board and face of the wall sheathing is 1/2”.
5 Wood structural panel sheathing, gypsum board sheathing, or foam sheathing is permitted between the ledger board and the band board. Stacked washers are permitted in combination with wood structural panel sheathing, but are not permitted in combination with gypsum board or foam sheathing. The maximum distance between the face of the ledger board and the face of the band board is 1”.
Through-bolts. Through-bolts must have a diameter of 1/2 inch. Pilot holes for through-bolts must be 17/32 to 9/16 inches in diameter. Through-bolts must be equipped with washers at the bolt head and nut. Bolts should be tightened 6 to 12 months after construction due to drying and wood shrinkage.
Expansion anchors. Expansion or adhesive anchors must be used for attaching a ledger board to a concrete or solid masonry wall, as shown in Figure 12. The bolt or threaded rod of expansion anchors must have a diameter of 1/2 inch, which in some cases may result in needing a 5/8 inch-diameter anchor. Expansion anchors must be installed in accordance with the manufacturer's instructions and must be equipped with washers.
Adhesive anchors. Approved adhesive anchors with a 1/2 inch-diameter threaded rod must be used for attaching a ledger board to hollow masonry, as shown in Figure 13. Examples of approved adhesive anchors include the Epcon Acrylic 7 by ITW Ramset/Red Head, and the HY-20 by Hilti. Adhesive anchors are also permitted with concrete or solid masonry installations. Adhesive anchors must be installed in accordance with the manufacturer's instructions and must be equipped with washers. Adhesive cartridges should remain on the jobsite for inspector verification.
Lag screws. The diameter, length, and shank of lag screws must comply with Figure 16. Lag screws must be equipped with washers and be installed in the following sequence:
1.
Drill a 1/2 inch-diameter hole in the ledger board and a 5/16 inch-diameter pilot hole into the solid-connection material of the existing house.
2. Insert the lag screw through the ledger board and into the pilot hole by turning. Do not drive with a hammer. Use soap or a wood-compatible lubricant if needed to facilitate tightening.
3. Tighten each lag screw snugly, but do not over-tighten so as to cause wood damage.
Figure 16
SECTION 10: FREE-STANDING
A deck that is free-standing does not utilize the exterior wall of the existing house to support vertical loads. Instead, an additional beam is provided at or offset from the existing house wall, as shown in Figure 17. If the edge of a deck footing is closer than 5 feet to an existing exterior house wall, the footing must bear at the same elevation as the existing wall footing as shown in Figure 17. For a house with a basement, a cylindrical footing (caisson) is recommended to minimize required excavation at the basement wall.
Figure 17
FREE-STANDING DECK
SECTION 11: LATERAL SUPPORT
A deck that is more than 24 inches above grade must resist lateral loads in accordance with the following:
Diagonal Bracing. Provide diagonal bracing both parallel and perpendicular to the beam at each post as shown in Figure 18. Where parallel to the beam, the bracing must be bolted to the post at one end and to the beam at the other. Where perpendicular to the beam, the bracing must be bolted to the post at one end and to a joist or blocking between joists at the other. Where a joist does not align with the bracing location, provide blocking between the adjacent joists.
Exceptions: Bracing is not required perpendicular to the house for a deck that is attached to the house with both a ledger board under sections 8 and 9 and the connection specified in either Figure 19 or 20. For a free-standing deck that is attached to the house as specified in Figure 21, bracing parallel to the house may be omitted at the beam adjacent to the house. All bracing may be omitted for a deck which is attached to the house in accordance with sections 8 and 9 or Figure 21 and which has all of its decking installed at a 45 degree angle to the deck joists.
Figure 18
DIAGONAL BRACING REQUIREMENTS
Figure 19
TENSION-TIE CONNECTION, WITH LEDGER BOARD
Tension-tie requirements. Tension ties, if used instead of perpendicular bracing as described above, must comply with all of the following, but are not permitted for free-standing decks:
1.
The deck joists and floor joists must be parallel.
2. At least 4 ties must be installed, at the end joist and first inside joist at each end of the deck as shown in Figure 19. A set of tension-ties must be installed for each structurally independent section of a multi-level deck.
3. Approved tension-ties include the LTS19-TZ from USP or DTT1Z from Simpson Strong-Tie.
4. The minimum capacity of each tension-tie is 750 pounds.
5.
Tension ties which are not available in a G-185 zinc coating require a barrier membrane separating the tension tie and the preservative-treated joist. The barrier membrane must be recommended for this location by its manufacturer.
6. Tension-ties must be attached to the underside of the joists in accordance with the manufacturer's instructions. Tension-ties must be attached to the exterior wall with lag screws as shown in Figure 19. Lag screws must penetrate a minimum of 3 inches into the sill plate or top plate of a wood-framed wall.
7. Where attaching to a concrete wall, lags screws may be replaced with adhesive or expansion anchors and a 1/2 inch threaded rod, with a withdrawal capacity of at least 750 pounds. The anchor must be installed in accordance with the manufacturer's instructions.
Figure 20
HOLD-DOWN TENSION DEVICE, WITH LEDGER BOARD
Hold-down tension devices. Hold-down tension devices, if used instead of perpendicular bracing as described above, must be provided in at least 2 locations per deck, and each device must have an allowable-stress-design capacity of at least 1,500 pounds.
Free-standing deck – attachment to house. Attach the deck's rim joist to the existing house exterior wall as shown in Figure 21 for a free-standing deck, if diagonal bracing parallel to the house is omitted, as described above. The wall must be sheathed with minimum 3/8 inch wood structural panel sheathing. Use lag screws or through-bolts if fastening to an existing band joist or wall stud; and use expansion or adhesive anchors if fastening to concrete or masonry. Do not attach to brick veneers. Verify this condition in the field prior to utilizing this method. Fasteners must be 16 inches on center and staggered in 2 rows. Flashing over the rim joist is required and must be installed in accordance with the flashing provisions in section 8.
Figure 21
ATTACHMENT OF FREE-STANDING DECK TO HOUSE FOR LATERAL SUPPORT
SECTION 12: DECKING
All decking materials must be wood or a wood-plastic composite and must comply with all of the following:
1.
Wood decking must be 2x4s, 2x6s, or five-quarter span-rated decking boards. Wood-plastic-composite sizes must be in accordance with the manufacturer's instructions. Plastic decking may be used if it is approved by a professional testing organization for supporting a live load of 40 psf and is installed according to the manufacturer's instructions.
2. Decking must be attached in accordance with Figure 22, and may be placed at an angle of 45 to 90 degrees to the joists unless disallowed in the manufacturer's instructions. If the decking is wet, place it with no gap so that after drying, a ?-inch gap is created.
3. Decking may overhang a joist by up to 3 inches unless disallowed in the manufacturer's instructions.
4. The center-to-center joist spacing may be up to 24 inches for wood decking, but may not exceed 16 inches for wood-plastic-composite decking unless specified otherwise by the manufacturer.
5. Each wood decking member must bear on a minimum of 4 joists or intermediate blocking between joists.
6. Placement and attachment of wood-plastic composites must be in accordance with the manufacturer's instructions.
7. Attach the decking to the rim joist in accordance with Figure 23.
Figure 22
TYPICAL DECKING
Figure 23
RIM JOIST CONNECTION
SECTION 13: GUARD AND POSTS
All open sides of a deck area that is more than 24 inches above grade – at any point within 36 inches beyond the edge of the deck – must have a guard that complies with Figure 24 and with all of the following:
1.
Required horizontal guards shall not have openings from the walking surface to the required guard height which allow passage of a sphere 4 inches in diameter, when applying a force of 4 pounds.
2. Required guards at stairs shall not have openings which allow passage of a sphere 4 3/8 inches in diameter, when applying a force of 4 pounds, other than the triangular opening at the side of an open stair formed by the riser, tread, and bottom rail of a guard, which shall not allow passage of a 6 inch sphere, when applying a force of 4 pounds.
3. Wet lumber must be spaced such that when shrinkage due to drying occurs, a compliant opening is maintained.
4. Rope, cable, or a similar non-rigid material may be used instead of balusters if it is strung with maximum openings of 3 1/2 inches and with vertical supports no more than 4 feet apart.
5. The guard and posts must withstand a 200-pound load applied in any direction.
6. Guard-infill components, such as balusters and panel fillers, must withstand a horizontally applied, perpendicular load of 50 pounds on any one-foot-square area.
7. Wood-plastic composites of equivalent dimensions may be substituted for the guard cap and infill elements shown in Figure 24 if the manufacturer's instructions permit this use.
Figure 24
GUARDS
Guard posts. Guard posts must be attached to the deck structure in accordance with all of the following:
Notching guard posts, as shown in Figure 25, is prohibited.
1. Notching guard posts, as shown in Figure 25, is prohibited.
2.
Hold-down anchors must have a minimum capacity of 1,800 pounds.
3.
Guard posts may be attached to either side of the end joist or rim joist.
4.
Bolt holes for a post must be at least 2 inches from the wood edge, at least 2½ inches apart, and no more than 5 inches apart.
5. Hold-down anchors, as shown in Figures 26 and 27, must be used to attach the guard post to the end joist and rim joist, respectively.
Figure 25
POST NOTCHING PROHIBITED
Figure 26
GUARD POST TO END JOIST
Figure 26
GUARD POST TO RIM JOIST
