Composite Decking

Four surfaces, and what each one asks of you

Pressure-treated pine is what most decks around here are wearing. It's cheap, it takes fasteners well, and it arrives wet. Left alone it goes gray, checks along the grain and lifts splinters.

Cedar is calmer. It moves less, it smells better and it costs more. It's still wood, so it still wants a coat on a schedule.

Capped composite is a wood-flour and plastic core with a hard shell around it. The shell resists stains and fading. The core is what makes it heavy and what makes it move with temperature.

PVC has no wood in it at all. It's the lightest, the most stain-resistant and the most obviously plastic underfoot.

Humidity, pollen and the yellow month

Georgia does two things to a deck that a brochure from Colorado won't show you. The first is moisture that never really leaves. Shaded boards over damp ground stay damp, and anything organic on a damp surface eventually grows.

On wood that becomes surface mold you scrub off. On composite it sits as a film on top of the cap, which is easier, but it's not nothing. The second is pollen.

For a few weeks every spring, every horizontal surface in the state turns yellow. Nothing you buy prevents it.

A washable surface is the only defense, and every material on this page washes.

Movement, and why gaps look wrong in January

Wood swells across its width when it gets wet and shrinks when it dries. Composite does the opposite trick. It changes mostly along its length, with heat.

That difference shows up at the ends of boards. A composite deck fitted on a hot afternoon is at its longest. Fit it tight that day and the boards have nowhere to go when the cold arrives.

So gapping is a calculation about the temperature on the day of the job, not a habit.

The frame has to suit the board

This is the part that surprises people mid-project. A composite board is stiffer than pine across a short span and softer over a long one. Most lines want the joists closer together than a wood deck needs.

Run the boards diagonally and that spacing tightens again, because the effective distance from joist to joist grows with the angle. None of that is a problem on a new build, where the frame gets laid out for the chosen board. It's only a problem when a surface is picked after the framing is finished.

Hidden fasteners, and what they cost you in time

A clip system leaves a deck with no visible screws. It also captures every board on both edges, so replacing a damaged board later means working in from one end.

Face screwing is faster, repairs easily and leaves a visible pattern. On pressure-treated wood that pattern is normal. On a capped composite it's what people notice.

Where to read next

The frame under any of this is on the deck building page, and if the existing frame is the question, start at deck repair.

Wood needs a finish and composite doesn't, which is the whole of deck staining and sealing. For a side-by-side view written for the person paying, not the person installing, read choosing materials, and the deck size and board calculator sizes the deck and counts the boards for each option.