How to Anchor a Deck

When building a deck one of the most overlooked steps is proper anchoring. Quite often people only nail the ledger board to the building. While this will hold the deck up temporarily while it is being built it certainly isn't adequate. It's not unusual to hear reports of decks collapsing and in the majority of cases the problem is inadequate anchoring.

Depending at what height the ledger board lands on the building will determine the correct type of anchoring. In most cases the ledger board will be fastened to the buildings wood framing. Here what is needed is a 1/2" x 3.5" lag bolt with the appropriate washer. These are available at all hardware stores and home centers. Galvanized bolts and washers must be used. They won't rust like standard steel bolts and will last much longer.

If the ledger is going to be connected to concrete a concrete anchor must be used. Shields are the most common type of concrete anchor. They are also available at all hardware store and home centers. Again galvanized must be used.

In new construction its best to lay out the ledger where the joists will land. This way the correct location for the lag bolts can be determined so they don't get installed where a joist will land. Two bolts per bay is adequate. Predrilling with the correct wood bit is necessary. Lagging the ledger board to the building is easiest done before any decking is installed. Otherwise it will have to be done from underneath which makes the task much more difficult.

The next area that needs anchoring is where the joists connect to the ledger. Being that the ledger is bolted to the building it makes perfect sense that the joists should be mechanically fastened to the ledger. Here you need to use the appropriate galvanized joist hanger on every joist. Galvanized nails must be used in the joist hangers. It is very important to fill every nail hole in the hanger as this is where it gets its strength.

Next the posts need to be anchored. Most all decks today should be built on concrete piers. This gives you the option of using galvanized post bottoms. An anchor bolt is placed in the cement when the piers are poured. Care must be taken to install the bolt where the center of the post will be. The post bottoms connect to this bolt and are nailed to the wood post.

As with all building related projects be sure to follow all applicable building codes.