Deck Design – Post Hole Layout
How to Layout Solid Foundation Support Using the 3-4-5 Method
This article is Part 4 of the deck design and building series. It explains laying out post hole locations and the ledger board: the same methods used by deck contractors.
Deck Design – Post Hole Layout
Building a backyard deck is a great way to boost property equity and reclaim unused space for some well-deserved leisure time. Why hire a deck contractor when this makes such a great DIY project? This article is part 4 of the deck building series and focuses on post hole layout for a solid deck foundation.
Part 1 of the deck building series covered deck design fundamentals, part 2 explained basic deck framing concepts and part 3 expounded on lumber sizing and spacing. That’s a crucial topic because it leads directly into this one – the posts that support the deck.
Squaring the Deck Layout
This assumes a rectangular, attached deck using cantilevered joists of a certain size. It’s also assumed that the joists start at one end of the home. If this is to be a deck on a concrete patio, the layout method explained here are still valid.
- Deck Terminology - A cantilevered deck means that the outside joists are attached to the ends of the ledger board, but the ends of the beams overhang the posts for a more attractive look.
The numbers used are to make it clear how to use the 3-4-5 method of getting a squared foundation layout (in this case, 6-8-10; but any similar multiple may be used).
- Make a mark on the house siding where one end of the deck will be located.
- Measure down the wall the distance of beam overhang. Hammer a nail half way in at this spot.
- Measure 6’ down the wall and hammer in a nail.
- Tie a string line to the first nail.
- Reel off a length of string longer than the deck will extend, and tie it to a 2” X 2” stake.
- Make a mark on the string 8’ from the nail.
- Tie another string to the second nail and mark it 10’ out.
- With strings taut, one person holds one string and another person holds the other.
- Move the strings until the marks intersect.
- Hammer in the stake. This spot is directly perpendicular to the house.
- Repeat the above process for the other end. A square area is now defined with respect to the home.
Find the Deck Post Locations
The number of, and distance apart, of the posts, has already been determined from the lumber sizing and spacing article. Now that knowledge will be used to find the deck post locations.
- For each row of posts parallel with the house, mark the two staked strings.
- With more stakes and strings, make a matrix, guided by the marks just made to establish the rows.
- Now, just mark the lines where the posts will be.
- Use a plumb bob and mark the ground with carpenters chalk or fluorescent spray paint.
Locate the Ledger Board
The dimensions of the joists and the distance of the home’s door from ground level are used in determining the location of the ledger board. In cases where the door is very close to the ground, the ledger is actually two pieces of lumber, one on one side of the door and one on the other. In this case, design the deck to be stepped up onto. Be sure to get the ledger board level using either a 4’ level or a laser level.
The next article covers setting and leveling the deck posts in fast setting concrete mix.
