Deck Design and Framing Concepts
Putting it Together: Hardware, Concrete, Posts, Beams, and Joists
Jan 16, 2008
Deck Design and Framing Concepts
In part 1 of the deck building article series, the topic of deck design fundamentals was covered. In this article, part 2, the focus is on deck design and framing. Deck building materials are also covered.
Deck Framing Materials
The deck understructure is what gives the deck not only its shape, but also its strength. The understructure is composed of posts, beams, and joists. Proper wood selection is the key for long life.
- Wood – Be sure to only select pressure-treated lumber. It should also be treated with an insecticide – a common one is chromated copper arsenate (CCA). Both southern pine and Douglas fir are good choices. It’s also a good idea to apply a brush preservative to wood surfaces that are cut or drilled.
- Hardware and Fasteners – These include deck screws, bolts, framing anchors, and nails. They should all be galvanized, but the deck screws should also have an additional resin coating.
- Concrete – Use premixed concrete. Quikrete Fast Setting Concrete Mix is the best choice and it’s readily available. Plan on using one to two bags per post depending on post depth. It’s always a good idea to dig the hole approximately 3” deeper than needed and lay in a bed of pea gravel. This will provide proper drainage away from the bottom of the post.
Framing an Attached Deck
For an attached deck, a 2” X 4” ledger board is attached to the house; it must be level. This will support one side of the deck; the remainder of the deck is supported by 4” X 4” posts.
Beams are fastened to the top of the posts parallel to the ledger board. How many beams and rows of posts are installed depends on the size of the deck and how much weight the deck is expected to bear. Special consideration must be given when hot tubs or other items are going to be supported by the deck. (Lumber sizes and spacing will be covered in the next article of the deck building series.)
Deck floor joists run from the outer beam to the ledger board. Use joist hangers on the ledger board and post caps on the beams to support the joists. Finally, a rim joist is attached to the open end of the joists.
Framing a Freestanding Deck
A freestanding deck is the same as an attached deck except that in place of the ledger board, a beam and a row of posts are used. This construction method is ideal for building a shed.
Weather and Climate Considerations
In areas where extended freezing periods are the norm, posts must be set a minimum of 8” below the frost line. At the other extreme, in areas where there is no danger of freezing, posts may be attached to precast concrete pier blocks. Whichever method is used, always consult local building codes.
 |
