Figure 1. The installation of bolts or lag screws, including their number and spacing, depends on the size of the deck deck joist span and other conditions given in the table footnotes. If bolted, the bolts must go completely through the deck ledger and house floor band joist and have nuts with washers tightly fitted. The installation of lag screws requires drilled pilot holes, correctly sized so the threads of the screw fully engage the wood and extend all the way through both the deck ledger and the house floor band joist.
Of course, the latest code provisions in the IRC should be consulted for the proper installation of bolts or lag screws See Figure 2 used as a deck ledger connection. Figure 2. When decks that are simply nailed to the house are loaded by occupants, vertical and lateral loads stemming from the weight and movement of the occupants can cause the ledger nails to bend or pull out of the wood sheathing and house band joist.
Decks have collapsed in this way with as few as one or two occupants present. The failed deck structure shown in Figure 3 depicts a case where the deck shifted laterally, away from the structure, and fell to the ground. Had the deck fallen vertically, the nails would have bent over. In this case, the nails are essentially straight, indicating that the nails withdrew from the wall before total collapse.
Nails used in withdrawal have limited strength, and may provide only enough support for the weight of the deck itself and not that of the occupants. Undoubtedly some nailed-only ledger decks are still standing probably because they haven't been heavily loaded to the IRC-anticipated 40 psf live-load about one person on every 2-ft. Due to the frequency of ledger connection failures constructed with nails only, it became apparent to researchers and engineers that ledger connections made with only nails could not be relied on to perform while meeting the loading requirements of the code for a residential deck, typically 50 psf total live plus dead load.
Prior to , an economical engineered design solution using lag screws or bolts for this application was not available. Due to recurring deck collapse cases reported in the news, Virginia Tech researchers, with input from the Journal of Light Construction, successfully tested deck ledger connections that were eventually adopted into the IRC and Virginia building code. Figure 3. Close-up of deck ledger that was connected to a structure with nails only.
Even though only lightly loaded by occupants, the deck shifted laterally, pulling the nails out of the supporting structure. This question can be answered in a few minutes.
If only nail heads are visible on the surface of your deck ledger, you most likely have a nailed-only deck ledger. The deck should be identified as unsafe, its use forbidden, and immediately repaired or replaced in accordance with the recommendations of a qualified designer or construction professional. Joist hangers are used to attach the ends of joists to the face of a beam or a ledger board.
If you identify a crown in the board, you should always install it upwards. How far should a lag screw go into wood? How much weight can a ledger board hold? The ledger is 10' long so every foot of ledger must be designed to carry at least lbs of load. Do I need a washer with a lag screw?
No nuts are required to install a lag bolt. A bolt is installed into a through pilot hole that is larger in diameter than the threads. A washer is used for both screws and bolts to increase the surface area in contact with the wood. This prevents the hex head from ripping into the wood and losing grip.
How deep should a lag bolt go? Can ledger board extends past House? If your ledger board will continue around the corner of your house, you will also have to remove the house siding corner post in addition to the siding. Sometimes, you may want to extend your ledger board beyond the house to function as a beam with a post connection at the opposite end.
How much can a lag bolt hold? Does deck ledger need to be one piece? They should have a washer or a large head. They are usually installed in a zig-zag pattern. Douglas Fir-Larch, Southern Pine. Never counter sink bolts. This will significantly weaken the ledger board. Be sure to know what you are connecting to.
Standard bolt patterns are based on a solid connection to a solid-sawn and fully supported band joist in the home. Lag screws that hit wall plates or studs may not be comparable. The fasteners must be compatible with pressure-treated lumber to prevent corrosion.
Typically, you will need to install your bolts alternating high and low 2" from the top and bottom of the ledger board. As a rule of thumb, bolts can be spaced 16" on center for supporting joist span up to 12' in length.
0コメント