How to Plan a Deck Frame

The frame is the part of a deck that has to be right. Once decking is on, changing your mind costs ten times more. Plan the frame carefully and build it dry before you set a single post.

Build the frame dry first

This is the single most valuable habit in deck building. Lay out the entire frame on the ground — posts, beams, joists — before you dig anything. You can move lumber around for free; you cannot move a cured footing.

The dry layout also lets you check for conflicts: a joist that lands where a door needs to swing, a beam that blocks a window, a footing in the path of a downspout.

Footing placement

Space footings 6 to 10 feet apart, closer for stiffer frames and higher loads. Check your local frost depth and go below it. Every footing needs a post base — an adjustable steel bracket that holds the post above grade and lets you set the frame height precisely after the concrete cures.

Set the footings high enough that the finished deck surface is at least 6 inches above grade at the lowest point. Anything less traps moisture and rot.

Beams and joists

A beam spans between posts. A joist spans between the beam and a ledger attached to the house. Any joist running more than a few feet without support needs a beam or blocking behind it.

Before cutting joists, work out your span: the distance from the ledger to the center of the beam. Look up your joist size and spacing in the span table and confirm the plan holds. A beam needs to land on the posts, not between them.

Blocking and hangers

Solid blocking goes between joists over bearing points to stop the frame racking. Joist hangers at every bearing are faster and, when fastened with the right structural screws, stronger than blocking alone. Both methods are code-accepted; hangers are easier for a first build.

At the house, every joist gets a hanger on the ledger — not just the ends. A joist that is only screwed or nailed through the ledger can pull out.

The build order

1. Mark the deck outline and post locations.
2. Dig footings below frost depth, place post bases, pour concrete.
3. Let the concrete cure — 24 to 48 hours before loading.
4. Set posts to height, attach beams.
5. Attach the ledger to the house with flashing.
6. Hang joists with hangers.
7. Add blocking and the rim board.
8. Do a final level check before decking.

The level check

Before decking goes on, walk the entire frame with a level. Check every post, every beam, and joists at several points. A frame that is level within 1/8 inch across the whole span drains correctly; one that is off by 1/4 inch ponds at the low corner, which is where boards start to cup and hold water.

This is the point of no return. Fixing a low post after decking means removing boards. Five minutes with a level saves half a day.

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