1.
Drill a ½-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.(See PDF for Figure)
Figure 16
LAG SCREW
SECTION 10: FREE-STANDING DECKS
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.
(See PDF for Figure)
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.
(See PDF for Figure)
Figure 18
DIAGONAL BRACING REQUIREMENTS
(See PDF for Figure)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 ½-inch threaded rod, with a withdrawal capacity of at least 750 pounds. The anchor must be installed in accordance with the manufacturer’s instructions.(See PDF for Figure)
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 two 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.
(See PDF for Figure)
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 ⅛-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.(See PDF for Figure)
Figure 22
TYPICAL DECKING
(See PDF for Figure)
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:
