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How to Build a Deck With Composites

Expert deck builders show you how to build a deck with composites and other rot-resistant materials for longevity. Your deck will also look better and require less maintenance.

By the DIY experts of The Family Handyman Magazine

Overview: Build your deck using composite and other low-upkeep materials

Your deck should be a place to relax, not a painful reminder of those looming weekends you’re going to spend sanding, painting and staining. So if you’re in the planning stages for a new deck, consider alternatives to wood.

You can build yourself a low-maintenance deck using the same tools as you would a wood deck, and similar techniques. But there are differences between low-maintenance and wood products. We asked our pros for some tips to help DIYers avoid expensive mistakes.

Deck-building consultants

Deck-building consultants

Meet Our Experts

We asked Randy Moe from Decks Unlimited, and Bob Januik and Matt Norden from Precision Decks, for some tips on working with low-maintenance deck materials. Altogether, these guys have built more than 1,000 decks, using every material imaginable. Ten years ago, about half their jobs were wood. Today they install low-maintenance materials on three out of four.

Flatten the joists to avoid a wavy deck

Most PVC and composite products aren’t as rigid as wood, so they don’t bridge imperfections in the framing as well. If some of your joists are higher than others, you might end up with a wavy surface. Our pros stretch a string across the deck joists to detect high spots and then plane them down with a power hand planer. This might seem like a pain, but it takes less than an hour and pays off with a better-looking deck.

When choosing composites, beware of dark colors

Boards with dark colors can get blistering hot when the sun is beating down on them. If you like to go barefoot, consider a lighter color.

Hide composite ends

Many PVC and composite decking products are not the same color all the way through, so you’ll want to cover the ends. One solution is to “picture frame” the deck by installing deck boards around the perimeter. A picture frame creates a professional look but does require some additional framing. One way to support the perimeter boards is to add an extra joist 5-1/2 in. away from the outside joist and then install a 2x6 on its side between the two joists.

Protect joists from rot

Pressure-treated lumber is rot-resistant, not rot-proof. Two places our pros often see deterioration are along the top edge, where the decking traps moisture, and in between two joists that have been sandwiched together. Rolling butyl tape over the top of the joists will add years to your deck’s framing. Choose a dark-colored tape; shiny silver and white are noticeable between the gaps. A 4-in. x 75-ft. roll will cost you about $20 at a home center.

Check your joist spacing

If you’re planning to replace old wood decking with PVC or composite, measure the joist spacing first. Most deck joists are centered 16 in. apart, which is the maximum span for most low-maintenance decking. If you plan to install your decking at a 45-degree angle, your joists may need to be 12 in. apart. You may also have to install more stair stringers. Check your product specs, and talk to your local building official before you buy.

Avoid random splices

If your deck is 24 ft. long, don’t use random-length boards and butt-joint them together. Install a splice board to create two 12-ft. x 12-ft. spaces instead. Your deck will look better and you’ll avoid the frustration of trying to splice the decking over joists. A splice board will also require extra framing. Do it the same way you would for the perimeter boards (one extra joist and a 2x6 on its side between the outside joist and the extra joist).

Hide the screws

When it comes to fastening PVC or composite decking, all three of our pros like the Cortex concealed fastening system. You just countersink the screws using the special bit included with the kit, and hammer in a plug that’s made of the exact same material as the decking. Screw holes virtually disappear, and damaged boards are easy to remove if you have to. A box of 350 costs about $80 at Home Depot.

Stair rails made simple

Stair railings are one of the trickiest parts of any deck project. Some aluminum manufacturers offer a preassembled railing that racks to whatever angle you need. Just measure the distance between the posts, transfer the proper angle and cut to length. If your rails fit into a sleeve, you can cut them with a hacksaw, recip saw or circular saw. If your rail ends will be exposed, you may want to invest in an aluminum blade for your chop saw. Either way, clean up the ends with a file so you don’t scratch things up during installation.

Mix and match

You don’t have to stick with one type of product or one look for the entire deck. Our pros mix and match all the time: composite posts with aluminum rails, composite rails with aluminum spindles. And don’t be afraid to think outside the box when it comes to color. You can install perimeter boards the same color as the railing. Choose a post color that’s different from the railing. Have the spindles be a different color than the posts and rails. The possibilities are endless.

Connectors make railings easier

Creating a tight fit between a composite post and a rail is difficult—even pros struggle with it. Railing connectors make it easy. This connector, made by Deckorator, is screwed onto the end of the rail before being attached to the post. It comes in five colors. You can buy these connectors from the same place you get your decking, or order them through our affiliation with amazon.com for less than $10 a pair.

Dress up an ugly post

If your deck is more than a couple of feet off the ground, you may want to wrap the posts in PVC to match the rest of the deck. You’ll need two 1x6s and two 1x8s for each post. Our pros avoid material thinner than 3/4 in. because PVC expands and contracts more than wood, and it’s hard to keep the seams together using thinner material. Pin the boards in place with a trim gun before screwing them together.

Dark, round spindles improve your view

Do you know why horse fences are usually white? It’s because dark ones are harder for horses to see. The same principle applies to deck railings and people. If you want an unobstructed view, dark spindles are the way to go. And round is better than square. A 3/4-in.-diameter round spindle stays 3/4 in. no matter what direction it’s viewed from, but a 3/4-in. square spindle grows to more than an inch when you view it at an angle.

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Required Tools for this Project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

    • Miter saw
    • Circular saw
    • Power plane
    • Drill/driver, cordless
    • Corded drill
    • Chalk line

You'll also need other tools for deck building.

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July 12, 4:50 PM [GMT -5]

too bad there's nothing about which composite materials are better than others, in terms of lifespan.

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