How to install composite decking

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 and check out some composite deck designs.

You can build yourself a low-maintenance deck using the same tools and similar techniques as you would a wood deck. And most parts of a deck are now available in composite material.

Tools required

Chalk line

Circular saw

Corded drill

Drill/driver – cordless

Mitre saw

Power plane

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.

Pro tip: This might seem like a pain, but it takes less than an hour and pays off with a better-looking deck.

Learn how to check a deck frame.

Boards with dark colours can get blistering hot when the sun is beating down on them.

If you like to go barefoot, consider a lighter colour.

Learn more on how to create the perfect deck.

Many composite decking products are not the same colour 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.

Pro tip: A picture frame creates a professional look but does require additional framing.

One way to support the perimeter boards is to add an extra joist 140mm away from the outside joist and then install a 2×6 on its side between the two joists.

Hide composite ends by mitring joints around the deck perimeter.

Add extra joists for support as needed.

Follow these tips for tighter mitres.

Pressure-treated timber is rot-resistant, not rot-proof.

Two places our pros often see deterioration are along the top edge, where the decking traps moisture, and between two joists sandwiched together.

Rolling butyl tape over the top of the joists will add years to your deck’s framing.

Choose a dark-coloured tape; shiny silver and white are noticeable between the gaps.

Lay butyl tape over the joist tops to help prevent rot.

If you’re planning to replace old wood decking with PVC or composite, measure the deck joist spacing first.

Most deck joists are centred 400-450mm apart, which is the maximum deck joist spacing for most low-maintenance decking.

If you plan to install your composite decking at a 45-degree angle, your joists may need to be 300mm apart.

You also may have to install more stair stringers.

Learn how to plan and build a deck.

Use splice boards to eliminate random splices in long runs.

If your deck is 7m long, don’t use random-length boards and butt-joint them together.

Install a splice board to create two 3.5m x 3.5m 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 2×6 on its side between the outside joist and the extra joist).

When it comes to fastening PVC or composite decking, our pros recommend a concealed fastening system.

This may vary depending on which decking your using, so take this into consideration before making your decision on decking.

Pro tip: Features like this make composite deck designs really look polished.

Stair railings are one of the trickiest parts of any deck project.

Some aluminium 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, reciprocating saw or circular saw.

If your rail ends will be exposed, you may want to invest in an aluminium blade for your chop saw.

Either way, clean up the ends with a file so you don’t scratch things up during installation.

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 aluminium rails, composite rails with aluminium spindles. And don’t be afraid to think outside the box when it comes to colour.

You can install perimeter boards the same colour as the railing.

Choose a post colour that’s different from the railing.

Find a complementary colour for your composite deck stairs.

Have the spindles be a different colour than the posts and rails. The possibilities are endless.