Composite deck materials add sophistication and durability to any deck. Here's how to install composite decking and railings.
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You'll need a solid frame for any type of decking. This deck has a frame made of pressure-treated lumber. If you need help with framing and setting the posts, see How to Build a Deck: Post Holes and Framing.
If you choose to install wood decking, you can find step-by-step instructions in How to Build a Deck: Wood Decking and Railings.
Follow all local building codes.
For composite decks, mount the posts to the inside of the joists.
Start by determining the number of posts you need and the post spacing. You should have posts by the house, at outer corners and at the top of the stairs. Measure the distance between two corner posts and divide by the distance allowed between posts. Round up to the nearest whole number, then subtract 1.
15 feet ÷ 5 feet = 3
3 - 1= 2 posts in between
Make sure the posts are evenly spaced. If one lines up over a joist, you can reposition it slightly.
Most codes permit a maximum post spacing of 6 feet.
Cut the posts to length according to your plan and local codes. The bottom ends of the posts will be flush with the bottom edges of the rim and end joists.
This deck has deck anchors attached to the joists, which makes for a stronger railing.
Along the end joists, use deck screws to attach extra bracing between the floor joists and end joists to mount the anchors. Cut the bracing from the same 2 x lumber you used for the joists (for this deck 2 x 8 lumber).
Your local code may specify a method of post installation.
Begin installing posts along an end joist. Screw a post in place, making sure it's plumb and extends to the bottom of the joist.
You can use clamps to keep the posts in position while you fasten them to the deck.
Mark the joist at the center of the post about 2 inches from the top and 2 inches from the bottom.
At the marks, drill two bolt holes through the end joist and post.
Insert the carriage bolt in the top hole, place the anchor and tighten the nut and washer.
Attach the anchor to the bracing with screws.
Secure a second bolt through the bottom hole. Each post should have two carriage bolts, but will only need one anchor.
Attach an anchor on the back of the bracing for added strength.
Continue installing posts. For posts in the corners, add bracing around the post and secure it with anchors. Again, cut the bracing from the same material you used for the joists (in this case 2 x 8 lumber).
Along the rim joist, add similar bracing behind the posts with screws and corner brackets, then secure the posts with carriage bolts.
Once all the posts are secured you can install the decking. For a cleaner look, use hidden deck clips and grooved composite boards. If you deck will have parting boards running down the middle, install decking on either side of the bracing you installed to support them. You'll trim the decking before installing the parting boards.
The hidden clips set a drainage gap between the boards.
Starting near the house side of the deck, use screws to secure the start / stop clips flush with the rim joist, spaced about every 16 inches.
Set your first board down, and push the groove over the clip prongs.
Next, at every joist, insert a clip prong fully into the board's groove and secure with screws.
Line up the grooves on the next board with the prongs, and push the board tightly into place. Overhang the boards by a couple of inches at the end joists. You'll trim them later. Continue installing the boards. Use a jigsaw to cut the decking and work around the posts as needed. You can make the cutouts a bit wide to help fit the boards in place — you'll cover the gaps later with post skirts.
You'll need someone to assist you with installation of long deck boards.
The last board might not need to be full width. Rip it — cut along the length of the board — to fit if necessary. If you're installing skirting, leave a 1-1/4-inch overhang. Set the board in place and attach with composite decking screws. Later you can cover the cut edge with a fascia board.
If you're not installing skirting, you can cut the decking flush with the joists. On the last deck board, you’ll have to rip it to fit and then cut a groove into the board with a router. To secure the board, place the start / stop clips in the groove and attach with screws.
To trim the deck boards to length, snap a chalk line along the end joist and cut along the line with a circular saw. Leave a 1-1/4-inch overhang if you're installing skirting.
A saw cutting guide helps you make clean, straight cuts.
At the center of the deck, cut the decking to fit the parting boards.
Secure the parting boards in place with composite decking screws. Use a screw to set a drainage gap.
Slide on the post sleeves. Cut them to height if necessary.
Glue post sleeve collars in place with PVC cement. Follow the package instructions.
Measure the distance between posts and mark both ends of each bottom rail 1/4-inch shorter, keeping the baluster hole spacing even between the marks.
Measure and mark the top rail in the same way.
Cut the rails to length.
Use PVC cement to secure a crush block centered on the underside of each bottom rail. Allow the glue to cure.
Slide the brackets and flanges onto a bottom rail. Hold the rail in place, trace the brackets on the posts and then remove the rail.
You can temporarily place another crush block under the bottom rail near the post to support the bottom rail at the correct height.
Reposition the brackets and flanges on a post and mark the holes. Drill pilot holes and secure the flanges with screws. Follow the same procedure on the other post.
Slide the brackets back onto the rails and lock the rails in place between the posts.
Put the end balusters in place as guides and set the top rail in place. Mark the bracket location and install the flanges as you did on the bottom rail.
Insert all the balusters and then lock the top rail in place. Attach post caps with PVC adhesive.
Install the rest of the railings.
Always follow the manufacturer's recommendations for fasteners and structural hardware.
Read more about pressure-treated lumber and wood preservatives on the EPA website:
It's time to attach the stairs. See How to Build a Deck: Composite Stairs and Stair Railings.
Watch the complete deck series at Lowes.com/BuildaDeck.