Building a deck
Who says natural is the only way to go? Occasionally humans invent something that not only lasts longer than Mother Nature's products but is easier to maintain. In this article, we'll tell you how to use some of these materials to build yourself a deck that will last a long time, look good and be easy to maintain. We'll also show you tricks and tips to make the building process simpler and “mistake-tolerant.”
Decks are great do-it-yourself projects, and this one, big as it looks, is no exception. Although this multilevel deck looks complex, you can build it using standard tools. A circular saw, drill, tape measure, chalk line, hammer and posthole digger can be adequate for building anything from a simple 12 x 12-ft. deck to an elaborate multilevel structure. But don't think you'll knock this one off in a couple of weekends. This deck took 12 skilled-carpenter days to build, so if you're new to carpentry, add a few days for the learning curve, weather delays, weekend-only work and family obligations. Realistically, a deck this size could turn into a summerlong project.
Our deck is 420 sq. ft. and cost $8,500 (in 2000) including the planters and privacy wall. Using plastic composite decking (we used Trex) instead of cedar or treated added substantially to the project cost, but when you figure that 15 years from now you'll be vacationing in Mexico instead of replacing the old deck, it doesn't seem so bad. For decking material pros and cons, see “The Case for Composite Decking” below.
Figure A: Main Deck and Assembly
Figure A shows the footing locations and framing details for the deck and the privacy fence. For a larger, printable version and a complete Shopping List, see Additional Information, below.
The key ingredients that will make your deck last (almost) forever
Photo 1: Testing the layout
Determine the size of your deck by laying out garden hose to mark its footprint (size and shape) on the yard exactly where it will be built. We used two garden hoses of different colors, one to lay out the deck and the other to lay out the planter boxes. Then pretend it's your finished deck by arranging chairs, tables, barbecue grills, or whatever else you expect to keep on it.
Photo 3: Mark the joist layout
Draw joist layout marks every 16 in. on the ledger board. Drill a pilot hole, then install a 3/8-in. x 4-in. lag screw between each floor joist. (Screw length may vary, but the screws should extend through the house sheathing and the rim joist of the house.) Stagger the lag screws in every other joist space to prevent the ledger from splitting.
Photo 4: Establish a square layout
Install batter boards outside the perimeter of each corner of the deck so that the center of the batter boards is “eyeball” square to the left and right ends of the ledger board. Stretch a string line at right angles to the ledger board at each end using the 3-4-5 triangle method (6-8-10 in this instance for more accuracy). Pound a small nail into the batter board where the string crosses it and tie the string to the nail. The string is a square reference guide parallel to the edge of the deck for laying out the rest of the framing.
Photo 5: Establish the beam locations
Measure from the deck ledger to position batter boards and strings for the beams that run parallel to the house. Mark the outside edge of the beam locations with the strings. Drive stakes into the ground to mark the center of each posthole (remember that the string marks the outside edge of the beam, not the middle).
Decking: The floor bears the brunt of rot on decks. Because deck boards lie flat, water collects in cracks and knots and soaks into the end grain—especially at splices. Because these areas stay wet for long periods of time, they are the most vulnerable to decay. Although we used Trex for the decking, we chose rough-sawn cedar lumber for the privacy wall, planter trim and other exposed wood to give the project a more natural, tactile character. Because these items are largely vertical, they can be made of wood and will last a very long time.
Lumber: The wood for all the above-ground framing is .40-grade pressure-treated lumber, which will last for decades without any maintenance. Posts and planter framing that are underground call for foundation-grade .60-treated lumber, the same material used for wood foundations. Foundation-grade material may be a special-order item in your part of the country, but most lumberyards can get it for you.
Hardware: Plan on spending a few extra dollars to get quality hardware designed for outside use. That means using double-hot-dipped galvanized nails or, better yet, stainless steel nails for all nailing, and exterior-rated joist hanger nails. You can also use special screws designed for composite decking or buy hidden fasteners designed for decking, though these get expensive. Install drip cap above the ledger and behind the siding (see Photo 2). Don't scrimp on hardware; remember that for the first time ever, the structure could outlast the hardware.
Design: Take pains to plan your deck for the long term. Think far into the future to get the size and shape right. Think in terms of a room addition more than a deck. We hired an architect and spent $500, a sum that bought us a site visit, a couple of preliminary drawings and final plans. He had numerous suggestions and ideas we wouldn't have thought of. With the design fee only 6 percent of the total project, it was a bargain.
Footings: Make sure your footings are deep and wide enough for your climate. When you take your plans in to get a building permit, your inspector will let you know about the local requirements. Here in Minnesota, that means 42-in. deep footings, but we went 48 in. to ensure that the deck would be able to handle the next ice age.
Structure: Build with shorter spans, narrower spacing and heavier materials than you would for a normal, wood deck. Our deck spans called for 2x10 beams and 2x8 joists, but we spent about extra and upsized the structural members to 2x12 beams and 2x10 joists to give a more beefy, permanent feel to what we expect will be an outside living room.
Call 811 to locate and mark underground utilities before digging.
Photo 7: Set the posts
Assemble the posts from foundation-grade 2x4s and 2x6s, nailing them below their future cut-off level—see Photos 8 and 9. Drop them into their holes and align them with the string line. Lay temporary 2x10s (joist material) alongside the posts to help position them. Plumb the posts both ways and tack them into the floor joists. Fill the holes, packing the dirt as you fill.
Photo 9: Cut the posts
Cut off one 2x6 and the middle 2x4 with a circular saw. If your posts will show, you may want to cut off the 2x6 away from the house. Complete the cut with a handsaw. Cut off the longer 2x6 even with the top of the ledger.
Cut the deck posts to the right height for the double beams.
Photo 10: Nail the beams
Set the double 2x12 beam on the posts and fasten it to the long 2x6 with 16d galvanized box nails. Nail the 2x12s to each other with three nails every 12 in., one close to each edge and one in the middle. Be sure the beam projects several inches past the edge of the deck for later trimming.
The soil at our site was a combination of loose sand, rocks and hard clay, so we ended up using a power auger, a steel bar to loosen rocks and a clamshell-style posthole digger to extract the rock and clean out loose soil at the bottom of the hole. A drain tile shovel is great for loosening the clay at the bottom of the hole and for dislodging rocks.
Power augers cost about $70 - $90 per day to rent, and they don't always make posthole digging a quick, easy chore. They take two strong people to run, and they bog down in heavy soil and skip over the top of any rocks bigger than a tangerine. They are, however, worth their weight in gold if you have lots of holes to dig—especially if you're digging in sandy soil. The corkscrew end on the auger will extract the dirt more efficiently than the clamshell digger because sand falls through the end of the clamshell blades when you're lifting the tool out of the hole. The pros usually end up hand-digging about 40 percent of the holes even if they do have a power auger at their disposal. If you choose to rent an auger, remember to hand-dig a pilot hole a few inches deep before firing up the machine. Otherwise the auger has a tendency to wander at startup and your hole might shift several inches off your layout.
Use construction-friendly building methods
Photo 11: Nail on the joists
Nail the first end joist (A) into the end of the ledger and square it to the ledger with the 6-8-10 triangle technique (Photo 4). Mark the beam even with the outside edge of the end joist, slide the joist away from the cut mark, draw a square cut-off line and cut off the end of the beam. Toenail the joist into the beam and measure from the joist to make 16-in. layout marks on the top of the beam for joist placement. Use the joist layout marks on the ledger as a guide to transfer marks to the beam for setting the joists. Install the remaining joists, toenailing them into the rim and beam. After you're satisfied with the joist placement, secure them to the ledger with joist hangers.
Photo 13: Cut the deck joists to length
Measure from the rim joist the depth of the deck, mark the end joists and snap a line for cutting off the ends of the joists. (When measuring, don't forget to subtract for the 1-1/2 in. thickness for the rim joist.) Draw cut-off lines with a carpenter's square and cut off the ends with a circular saw.
Photo 14: Nail on the outside rim joist
Nail the end rim joist onto end joist (A) and have your partner raise and lower the rim joist to make the top edge of the rim flush with the top edge of the joists. Nail each joist, working your way from end joist (A) to end joist (B). Cut the end of the rim off flush with the end of the last deck joist.
Photo 15: Fasten the decking
Fasten the decking with ring-shanked 10d stainless steel nails, composite decking screws or hidden fasteners, working from the outside of the deck toward the house using 16d nails for spacers. Let the decking hang over the end joists at least 2-1/2 in. Measure from the house side of the deck every five or six boards to confirm that the decking is running parallel to the house (distances A and B) and make small spacing adjustments as necessary. Leave off the last piece of decking because the house will block the last cut made by the circular saw.
Follow the photo series for step-bystep building techniques and keep these labor-saving tips in mind when planning and building your deck.
- We employed cantilevers (beams hanging over posts, and joists hanging over beams) in our design because they make layout and construction much easier. They also give the deck a floating appearance by moving the main structural supports in from the deck's perimeter. Cantilevering also helps by providing “fudge factors” throughout construction. They allow you to fine-tune the dimensions of the deck as you build. Non-cantilevered decks require exact placement of posts at each corner from the moment you dig your first posthole. Unfortunately, all too often you discover only after setting the posts that footing and post placement is off by several inches. You're then faced with living with an out-of-square deck or making some very time-consuming fixes.
- Begin construction by installing the ledger board. (Don't forget the drip cap! See Photo 2). Use the ledger for laying out the rest of the deck, including posthole placement.
- Don't cut anything until you have to. If possible, install members before cutting them to length to give you the opportunity to make minor adjustments in the structure as you build. That means installing posts longer than they have to be, running beams longer than the deck is wide and attaching joists to the ledger before cutting them to their finished length.
- Make your deck at least 6 in. smaller than the standard 2-ft. increments of lumber. We made our 12-ft. section of deck 11 ft. 6 in. and our 16-ft. section 15 ft. 6 in. This lets you trim bad ends on deck boards, maintain a 1-in. overhang along the edges, and install cedar trim boards to hide the treated lumber framing.
The Case for Composite Decking
Decks used to be built solely of redwood, cedar or cypress because of their inherent wood preservatives. But as some of us have learned the hard way, all wood eventually rots—especially in shady, moist locations.
For many years, preservative-treated lumber has been the accepted material for a long-lasting, rot-resistant deck. But treated wood has its downsides too. Besides not being particularly attractive, it has a tendency to split, warp and twist (and those treated splinters embedded in the bottom of your hoofs are no picnic either).
There are now alternatives to conventional treated and natural wood. Various manufacturers sell different versions of plastic or composite plastic/wood decking. You'll find everything from basic, square-edged composites to elaborate space-frame vinyl and fiberglass extrusions with, of course, elaborate prices. Matching posts, railings and trim are also available for most types. These products are not available in all areas. You'll need to visit the lumberyards in your area to see what your choices are. For more information on options, see How to Choose Composite Decking.
We chose Trex composite decking for this deck because of its wide availability and reasonable price. The decking material we used is the classic 1-1/4 x 5-1/2 in. shape of conventional wood decking. (Visit trex.com to see the latest colors and styles.) In addition to decking, many composites are available in a variety of non-structural dimensions such as 2x6s and 2x4s, which you can use for benches, rails or privacy screens. Composite decking is generally limited to 16-in. spans, so the joists need to be spaced every 16 in. instead of the more common 24 in. used for wood 2x6s. Composite decking can be cut and drilled and shaped just like actual wood, so no extra tools are necessary.
Composites are denser and heavier than wood. Consequently, they're harder to haul around and a bit harder to drive fasteners into. The good news is that they won't split, warp, twist, cup or crack—ever. The surface is skid-resistant even when wet, and you'll get that warm, fuzzy feeling knowing that fewer trees gave their lives for your deck.
Splice decking with a single seam
The typical way to handle a deck that is wider than the deck boards is to randomly butt the ends together and split them over a deck joist. Cutting and fitting all these joints takes a lot of time and forces you to butt two boards tightly together to share the 1-1/2 in. thickness of a floor joist. Nailing close to the ends makes wood split and rot prematurely because moisture gets into the splice and doesn't dry out for long periods of time.
A more elegant, longer-lasting way is to create a single seam with a dogeared length of decking perpendicular to the deck itself. Then toenail in another floor joist for nailing the ends of the next section. Having a full 1-1/2 in. of joist for nailing each deck board allows for a space between the end of the decking board and the splice board for drying, and helps keep nails away from the splitting zone.
Figure B: Planter
Planters make a striking addition to the deck, and also create more privacy, making the deck feel almost like a separate room. For a larger, printable version of Figure B, see Additional Information, below.
Think through the rail, planter and step details or they'll trip you up later
Photo 20: Dig trenches for the planters
Dig trenches 6 in. deep and 12 in. wide and fill with gravel. Measure down from the deck to keep gravel levels within 1/2 in. of desired height. Lay down .60 foundation-grade lumber for footing plates a few inches longer than the intended planter length and width. To set the footing plates, measure down from the deck and pound on them with a heavy board. Use a 4-ft. level, working off the first plate when setting the plates that don't adjoin the deck.
Photo 21: Square the planter walls
Lay out all pairs of plates on walls that face each other so that the braces are square when you attach them to the studs. Nail the studs to the top and bottom plates and nail on the plywood after first fastening it to an end stud of the wall. Then square the wall by working the plywood up and down to align the bottom of the plywood with the bottom of the plate, nailing across the bottom from the fastened end toward the other end. Finish nailing the plywood to the studs and the top plate every 8 in.
Photo 22: Add cross braces
Cut 1-5/8 in. x 3-5/8 in. holes for the 2x4 braces halfway up the wall every 32 in. Cut 2x4 braces the same length as the width of the wall, slip them through the walls and lag-screw them to the sides of the studs before standing them against the deck (they may be inaccessible later, depending on the height of your deck and planters).
Photo 23: Fasten the corners
Tack the corners together with 16d nails. Fasten the ends of the walls with three equally spaced 3-in. lag screws to tie the corners together, and one 3-in. lag screw through each wall brace. Cut and nail tie plates so that the tie plates overlap adjoining walls. Nail with two 16d nails over each stud.
Photo 24: Side the walls
Install treated 1x6 boards at grade to protect cedar from ground contact, then top with 7/8-in. Z-flashing to keep water from getting behind the siding. Nail 2x4 corner boards, positioning the tops flush with the top of the framing and install 2x2 horizontal trim boards between the corners. Side the walls and cap with 2x10s.
Photo 25: Build the fence
Notch 4x4s and decking and cut 4x4s to length (4-ft. 10-1/2 in. above deck). Plumb posts with a 4-ft. level and bolt to rim of deck after predrilling 1-in. countersink hole and boring a 3/8-in. hole through the post, cedar trim and end joist. Nail on a 2x6 top cap and install premade panel assemblies by toe-screwing into the side of the posts.
Most building codes call for 36-in. high guardrails on any deck that's more than 30 in. above ground and any set of stairs that has more than three risers. Our deck had only one side higher than 30 in., so we decided to handle that area with a 5-ft. privacy wall (Photo 25) to provide a safety rail and to screen the deck from a nearby road. You can copy this design, or use the one shown in Deck Privacy Fence.
For the rest of the deck perimeter, we built planter boxes in lieu of railings (Photos 20 – 24) because we didn't want our lake view obstructed. We also liked the idea of being surrounded by a deck-level flower garden. Frame the planters like a conventional stud wall made of foundation-grade lumber and rest them on a gravel footing. It's important to make the planters freestanding. The lack of a frost footing means they'll rise and fall with frost movement and will lift the deck if they're attached to it. Don't consider them as legal guardrails but as a passive barrier to keep people from accidentally stepping off the edge. They were designed so the tops were 15 in. above the deck to double as casual seating.
Tips for laying out and cutting deck stairs are available in How to Build Deck Stairs. We added some cosmetic side stringers (Photo 26) to dress the stair sides and decked the treads with Trex. Rest the steps on a gravel footing topped with a treated 2x10 (Photo 26) using the same setting methods demonstrated for the planters (Photo 20).