Deck board patterns and direction

The rule that governs every pattern

Decking must cross its supporting joists, and the unsupported distance between those supports has a limit set by the board — 16 inches for most 5/4 wood and nearly all composite, 24 inches for 2x wood decking.

That single rule decides everything below. Any pattern that increases the distance a board spans between joists has to be compensated for by closing the joist spacing or adding blocking. Get it wrong and the deck feels soft underfoot, and with composite it voids the warranty.

Straight boards, perpendicular to the house

The default. Joists run away from the house, boards run parallel to it, everything is at right angles. Lowest waste, fastest install, cheapest framing.

The only real decision is board direction relative to the longest dimension. Running boards the long way means fewer, longer boards and fewer butt joints; running them the short way means more rows. Where the deck is longer than the available stock, boards the short way avoids joints entirely.

Diagonal at 45 degrees

A diagonal layout is visually effective and hides the fact that a deck is a plain rectangle. It has two costs.

First, the framing. A board crossing the joists at 45 degrees spans further between them by a factor of about 1.41, so a joist spacing of 16 inches has to close to about 11 or 12. That is a third more joists, a third more hangers, and a third more framing labour. The joist spacing calculator works out the required spacing for a given angle.

Second, the waste. Every board is cut at an angle at both ends and the offcuts rarely fit anywhere else. Budget 15 percent waste rather than 10, and more on a small deck where there is less opportunity to reuse a cut end.

Picture-frame borders

A border board running around the perimeter, with the field boards butting into it, hides every cut end and makes a deck look considerably more finished. It is probably the highest-value upgrade per dollar on any deck.

What it needs underneath is blocking. The border runs parallel to the joists on two sides, so there is nothing beneath it to fasten to and nothing supporting the field boards' ends where they meet it. The solution is a row of blocking set inboard of the rim on those sides, which the border and the field board ends both land on.

• Plan the blocking during framing, not after. Retrofitting it from below is unpleasant work.
• A double border looks deliberate and is barely more work than a single, because the blocking is already there.
• Mitre the corners for a clean job; butt joints at the corners always read as a shortcut.
• Allow the same board gap where the field meets the border as everywhere else, so drainage is continuous.

Herringbone and chevron

Both create a woven or arrow pattern from short boards laid at opposing angles. They are striking, and they are the most demanding layout to frame.

Every board end has to land on support, and in a herringbone the ends land all over the deck rather than in lines. In practice that means joists at 12 inches on centre plus blocking, or a full sheathing layer, and a great deal of cutting. Waste often reaches 20 percent. It is a pattern worth doing on a small feature area rather than a whole deck.

Cost summary

Run your own board count for any layout with the deck board calculator, and check the gap and last-board width with the board gap calculator.