Composite Decking in Full Sun: How Hot It Gets and What Helps

Yes, composite decking gets hot in direct sun, and it usually gets hotter than pressure-treated wood or cedar, especially in dark colours. The colour of the cap layer and how many hours of sun the deck receives matter most. In Ontario the problem shows up on hot July and August afternoons, mainly on south and west facing decks. Lighter colours, shade and a sample test keep bare feet comfortable.

How hot does composite decking get in the sun?

Any deck surface warms up in direct sun. Composite warms up more than most wood, and it holds that heat longer after the sun moves on. No honest single temperature exists, because the result depends on the colour, the air temperature, the wind and the board itself. Be wary of anyone who quotes one number for every deck.

What you can count on is the pattern. On a hot, sunny day a dark capped board in full sun can be too hot for bare feet. A pale board in the same spot is far easier to stand on. Surface temperature is also not the whole story. A dense, hard material passes heat into skin quickly, while wood is a better insulator, so a wood board at the same temperature feels gentler.

The trouble window is short. Spring and fall are rarely an issue. The uncomfortable stretch is a handful of hot, humid afternoons in July and August. Boards cool quickly once the sun swings round or cloud rolls in, which is why a deck that is too hot at 3 p.m. can be pleasant by supper.

Do composite decks get hotter than wood?

In most conditions, yes. The table gives a rough guide to how common decking choices behave in direct sun. It is a comparison, not a measurement.

Choose composite if you accept a hot spell or two in exchange for less upkeep, and you are willing to pick a lighter shade or add shade. Choose wood if a cooler surface in full sun matters more than skipping the staining. Our composite vs pressure-treated wood comparison covers the other trade-offs.

Why colour, cap and board type change the heat

Four things decide how a composite board behaves in the sun.

• Colour. This is the biggest factor. Dark pigments absorb more sunlight and pale ones reflect more. Inside one product line, the darkest and lightest shades usually show the widest gap.
• The cap. On capped boards the plastic cap is the surface you walk on, so its pigment and finish set the surface heat. Some makers sell lines marketed as cooler. Ask for the maker's own test data for your exact colour and how it was measured, not just a label that says cool-touch.
• Board profile and density. A solid, dense board can store more heat than a lighter, grooved one. Ask how the maker's profiles compare rather than assuming.
• Exposure. A west facing deck with no shade takes the afternoon sun at full strength. The same boards on a north or east side may never be a problem.

Heat also makes composite boards expand. That is why makers specify gaps at the ends and sides of each board. Follow the installation instructions closely, because boards laid too tight can buckle on a hot day. Ask the maker, too, whether the warranty limits damage from strong reflected sunlight off windows or glass doors next to the deck.

How to keep a composite deck cooler in summer

You have several options, and the first two do most of the work.

1. Choose a lighter colour. It is the one fix you cannot add later without replacing boards.
2. Add shade. A pergola, an awning, a shade sail, an umbrella or a mature tree over the seating area cuts the sun that reaches the boards. If the cover is attached to the house or roofed, ask your building department first. Kitchener and Waterloo both list a roofed deck as needing a building permit.
3. Rinse the boards. A spray of water cools the surface for a few minutes. It is handy before kids go out, not a long-term answer.
4. Lay a light outdoor rug or runner along the paths and play areas people cross barefoot.
5. Leave airflow under the deck. Open framing lets boards shed some heat from below and keeps the frame drier. Do not box the space in tight.
6. Place seating where the afternoon shadow falls, usually along the house wall on the east and north sides.

Painting or staining composite boards to change their colour is not a reliable fix, and it may affect the warranty. Ask the maker before you try.

Test colour samples in your own yard before you choose

A showroom board tells you little about heat. Your yard tells you a lot.

1. Ask your deck builder or supplier for full-size sample boards in the shortlisted colours. Add a piece of wood if you are weighing both.
2. Lay them on the ground in the spot where the deck will sit, in direct sun.
3. Check them on a hot afternoon, after they have sat in the sun for an hour or more, with the back of your hand and then a bare foot.
4. Think about when your family uses the deck. A deck used mainly for evening dinners can take a darker colour than one where the kids play all afternoon.

Also look at the sun path. Mark which hours the deck sits in full sun in July. If shade from a tree, a fence or the house covers it from mid afternoon on, the heat problem shrinks. If it bakes from noon to evening, treat colour and shade as design decisions, not afterthoughts.

Kids, pets and bare feet: what to watch

Children and pets do not judge a surface the way an adult does. A toddler will run across a hot board, and a dog's paw pads are bare skin. Put the back of your hand on the board and hold it there for a few seconds. If you cannot keep it there comfortably, bare feet and paws should not be on it.

A few habits help. Keep sandals or water shoes by the door. Put a shaded, light-coloured play area on the cooler side of the deck. Wet the boards before kids play, and move pets to grass or shade during the hottest part of the day. Stairs, railings and a barbecue next to the boards can be hot too.

If a deck has already been built and the boards are too hot, shade and a rug are the quickest fixes. Replacing boards is the last resort. Our list of deck warning signs helps you decide when a deck is due for work for other reasons.

Planning a new deck: ask these questions first

If you are choosing between composite and wood, bring sun exposure into the conversation early. D&D Exterior Finishing builds decks in pressure-treated wood, cedar, composite and aluminum, and the free written estimate lists the materials and colours before work starts, so you can compare options on paper.

Questions worth asking any deck builder:

• Which side of the house gets the afternoon sun, and how does that affect the colour you would choose?
• Can I see full-size samples in the colours you recommend?
• What does the maker say about heat, expansion gaps and reflected light near my windows?
• Where could shade go, and does it need a permit?

Our guide to choosing a deck builder in Kitchener-Waterloo lists other checks for a quote. To see what we build, visit the deck building service page.

Hot deck questions homeowners ask

Does composite decking get hotter than wood?

Usually yes. In direct sun, capped composite tends to get hotter than pressure-treated wood or cedar, and it holds the heat longer. Dark colours show the biggest gap. A pale composite board in the same spot is much closer to wood. Dark-stained wood can also get hot, so colour matters for every material.

What colour composite decking stays coolest?

Lighter shades such as pale grey, sand and off-white reflect more sunlight and stay cooler than browns, deep greys and near-black boards. The difference between the lightest and darkest colours in one product line is often large. Compare sample boards side by side in your own yard, in the sun, before you choose.

Is composite decking too hot for bare feet or dogs?

It can be on hot, sunny afternoons, especially in dark colours with no shade. Press the back of your hand on the board for a few seconds. If that is uncomfortable, it is too hot for bare feet and paws. Shade, a light rug and a water rinse help.

Can you cool down a hot composite deck?

Yes, in small ways. Rinsing with water cools the surface for a few minutes, and shade from a pergola, awning or umbrella lowers the heat that builds up. A light outdoor rug helps on paths. Do not paint or coat the boards unless the maker approves it.

Devon Moore, Operations Lead Co-Founder & Operations Lead — D&D Exterior Finishing

Devon Moore is the co-founder and Operations Lead at D&D Exterior Finishing, specializing in siding, roofing, windows, and exterior renovations across Waterloo Region.