Here are five simple critical inspections that a homeowner can do to determine if their deck is safe.
#1: Ledger Attachment
The ledger board is one of the most important boards on a deck. It should have two lags with washers every 16”, 19.2”, or 24” on center. If it is nailed, it is only a matter of time before it falls off. House floor joists can be 16”, 19.2”, or 24” on center. Lags need to hit into the house floor joists. Just because you see a lot of lags doesn’t mean that they hit something solid.
#2: Joist to Ledger
Joist hangers hold the joist to the ledger board or rim joist so make sure all joists have a joist hanger on them. If you don’t see joist hangers, you should not use your deck. Every nail hole should be filled with special joist hanger nails. Joist hanger nails are thicker, stronger and have more shear strength than other nails. Screws should not be used in hangers unless they are approved joist hanger screws. All outdoor connectors, hangers, bolts, lags, nails and screws in contact with treated lumber should be hot-dipped galvanized, stainless steel or triple coated zinc polymer steel. When using stainless steel connectors you must also use stainless steel fasteners.
#3: Beam to Post
Connections should always be bolted with a minimum of two in each post, or four if there is a splice. Carriage bolts should be ½” in diameter. Never use nails or screws. You can also use special heavy-duty post brackets that are made for this.
If your deck shakes, wobbles or sways, it probably does not have cross braces on the posts or under the joists. For appearance and strength, use 2×4’s flat underneath (bottom side) the floor joists. They should go from the ledger board to the rim joist or beam. Use a cross brace with two nails or screws per joist.
#5: Railing Post to Deck
If your railing is the type with 4×4 posts, each post should have a minimum of two carriage bolts each. The post must not only be fastened to the rim joist, but also tied back into the joist framing. 4×4 posts should never be notched.