A single post can serve four functions:
(a) be part of the balustrade, (b) help support the deck, (c) provide a frame
work for installing lat
tice, and (d) support the stair stringer.
tangle of the deck. To hold the rim joist in place, I clamp 2x4 blocks under the end of each end joist, creating small shelves at both ends.
Installing the rim joist is then a piece of cake, because both ends are supported. On some decks, I attach the rim joist temporarily, mark the footing locations, and then remove it while I'm digging the footings. (I often do this on low decks, where the rim joist would interfere with the digging.)
The Footings and Posts
The deck structure is now a level and square rectangle held up by
Balustrade
Stair stringer
OUTSIDE STRUCTURE
Laying Out
Large Decks The width of a deck is usually limited to the span of the joists (typically 1 6 ft. or less). The length of the deck. on the other hand, can easily be made as long as the house. To build a modest, 1 6-ft.
long deck. I use the rim joist both to lay out the locations of posts and to suspend the posts while I pour the concrete footings. But what do I do when I have to build a much longer deck. where the rim joist has to be pieced together from two or three boards? I use string.
After installing and squaring up both end joists as described in the text, I set up a string that extends from the top, outside corner of one end joist to the top, outside corner of the other. Next I hook my tape measure over one of the end joists and mea
sure and mark the post locations on the string. (I mark the layout on the string with a felt-tipped marker; if the tape measure won't stay put on
temporary supports. The next step is to install the permanent posts.
I mark the location of the posts on the perimeter joists (the end joists and the rim joist), then transfer those locations to the ground with
DECKS
the joist, I clamp it down.) After transferring the layout from the string to the ground, I lay out and dig layout and cutting for later. I begin by mixing a batch of moist but stiff concrete. I pack 8 in. of this mixture in the bottom of the footing then set a post on the concrete. After making sure that the post will be long enough (39 in. above the string) to accommodate the balustrade, I brace it plumb in both directions and even with the marks on the string.
With the post securely braced, I pour a wet, mushy batch of concrete around the post until it's level with the surface of the ground. After the concrete cures, I cut the notch and the top of the post as it stands.
a plumb bob. Experience has taught me to think about more than just providing support for the deck when I plan the locations of the posts.
If I intend to underskirt the deck with lattice, for instance, I make sure the posts are no more than 8 ft. apart, which is the length of a sheet of lattice. If I'm going to build a set of stairs, I add a post to support each stringer. Finally, if I plan on having the posts extend through the deck and serve as newels for the balustrade, I make sure the posts are no more than 8 ft. apart. (Keeping the space between the newels under 8 ft.
lessens the chances that the rails will sag or bow and provides for a strong, safe balustrade.) I often use the same post for all of these func
tions (see the drawing on p. 1 29).
After
I
determine where I want the posts, I mark their locations on the perimeter joists. This process is simply a matter of pulling the tape measure from the outside corners of the propped-up perimeter. Next I lower a plumb bob and transfer the layout to the ground. Based on this layout, I measure and mark the outline of each footing, which I make 1 6 in. square.In my part of the country, the foot
ings only need to be 20 in. deep to get below the frost line. The clay soil that predominates here yields readily to hand tools, so I rarely spend more than 30 minutes dig
ging each footing by hand. When I'm done, the excavation is neat, with plumb sides, a flat bottom,
T R I C K S O F T H E T R A D E
Digging
Tools When you dig the footings for a deck, the goal is not to move dirt-it's to carve a clean opening in the ground, with a level bottom and plumb sides. I've found thot the best tools for this job are a small, square shovel, a one-hond mattock, and a couple of different
sized brick trowels. I olso keep a large poir of loppers handy for cutting tree roots.
and no loose soil-the perfect form for the concrete. Having built as far north as Maine, however, I know that things aren't always so easy. If you live in a cold region and/or have to contend with diffi
cult soil, you may want to use exca
vating equipment (see the sidebar on p. 1 32).
When I finish digging, I pour the footings and install the posts. I do these things at the same time, so the bottom of the post is embedded in the concrete. Although this prac
tice is approved by most building codes, some carpenters object to it because they're concerned about the long-term effects of leaving the post in contact with the concrete.
The main concern is that the base of the post will absorb moisture
OUTSIDE STRUCTURE
Building Decks in Cold
Climates In cold climates, where the frost line is more than 3 ft. down, it often makes sense to bring in a backhoe or an auger to dig the foot
ings. When you use excavating equip
ment, you can't dig the footings with the perimeter joists in place because you need room for the machinery.
So take down the perimeter joists after you've laid out the footings on the ground, bring in the excavator, and dig the footings. When you're done, it's surprisingly easy to reinstall the perimeter joists, especially if you've been able to leave the goal
post-shaped supports in place (see
PI'.
1 25- 1 2 7).There are two other things to consider if you're building in a cold climate.
The first is the concrete at the base of the posts. Where deep freeze occurs, the ground expands upward, or heaves. If the sides of the con
crete are jagged-as they would be if you used the excavated hole as a form-the heaving soil might grab the sides of the concrete and lift the entire deck. It's good practice to use concrete tubes or build wood forms to create smooth sides when you pour concrete around the bottoms of the posts.
DECKS
The other consideration is the height of the deck. Where heavy snow is expected, it makes sense to build the deck one step (7 in.) down from the top of the doorsill. This space makes it easier to open an outswinging door (usually a storm door) after a bliz
zard and keeps melting snow from seeping through the door opening.
Because building the deck at this height frequently places over half the band below the top of the foun
dation, there's a good chance you'll have to drill through the foundation to bolt the band to the house. If you're building a new house and you know where the deck will be, you can save yourself a lot of work by embedding these bolts as you build the foundation. Or, if you prefer, embed treated wood in the founda
tion to receive bolts when you install the band.