Blocking Joists for Decks

Blocking a deck increases the strength of deck frames that make use of long joist spans. Blocking is typically a technique reserved for larger decks, but it can be used on any deck to strengthen the structure. If you expect your deck to need to endure heavy loads like a hot tub, you should probably block your deck. This is easier to do while the deck is being built, but blocks can be added to an existing deck.

Tape measure
Wood that matches species and dimensions of the joists of the deck, probably 2-by-6 southern pine
Circular saw
3-inch wood nails
Hammer
Chalk line

Instructions

- 1
  Chalk a line along the underside of your deck along the joists, at the middle of the span. Make sure this line is bold and clear, as this will define where you put the blocks.
- 2
  Cut the wood to fit between joists using the circular saw. So if your deck is made of 2-by-6 joists, and the joists are 16 inches apart on center, your blocks should be 14 inches long.
- 3
  Nail the blocks under the deck one at a time, aligning them in a staggered pattern with the chalk line. Put the blocks about an inch off the chalk line on alternating sides. Hammer nails through the joist, into the ends of the block. Put two nails in either side.

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