Floor Joist Spacing For Deck Boards

If the floor joists that span the length of your deck are installed too far apart the boards on top will sag.

Floor joist spacing for deck boards.

The bigger you make your deck the more you ask of the framing timbers that hold up the deck s structure and the joists and beams that support the. Why the proper deck board spacing is important. Then using the lumber size of joists and the joist spacing determine if you are within the maximum allowable joist span. Why is joist spacing so important.

The larger the deck the larger the joists. Decide whether the joists will cantilever over or not. If adding additional framing be sure to keep all boards level and in plane across the tops. The last board won t look good if it s skinny or cut at an angle.

For best results refer to our wood and composite deck joist span table. A house is only as strong as its foundation and a deck is only as strong as its frame. If you will run decking at an angle you might need to put the joists closer together. Determine the decking board thickness and direction to determine joist spacing.

If you use 5 4 decking joists must be no farther apart than 16 inches. Decking boards span from joist to joist. In most cases it s best to start with a full board on the outside edge of the deck and work toward the house so the odd board is less visible. Table 1 2 or table 1 3 3.

I asked my local building official how he checks a deck plan to make sure the joist size and spacing combination will meet requirements of the building code he goes to the 40 lb. Recommended beam joist spans for deck framing. For a more rigid feel 12 or less may be preferred. While the gap in your deck boards may seem like a small step in a deck project the gap size you choose serves a significant purpose.

Adjust the spacing between deck boards gradually over the next 10 rows of decking until the distance to the house is equal. This helps to keep your deck s framework dry and rot free. Deck board spacing provides airflow through your decking allowing evaporating air to escape. Live load floor joist span tables in chapter 7 of the state residential code based on the 2012 international residential code.

Deck joists have a different maximum span length depending upon the size spacing and framing material that you re creating your deck with. In typical deck construction with a ledger on one side of the joist and beam on the other the size of the joists is driven by the size of the deck and based on the general maximum spans mentioned above. Here s a helpful chart covering the most popular wood framing species and their maximum allowed spans.