Temperature of Composite Decking
Look at the bottom step of the Trex Transcend decking. It's 152.3 F! That's hot enough to cause burns to bare skin in just seconds. (This important column was featured in the August 1, 2021 Newsletter.) Copyright 2018 Tim Carter
"I think the decking can get to over 160 F, or more, the closer you are to the summer solstice. "
Temperature of Composite Decking - Can Cause Burns Fast!
The temperature of composite decking is hotter than you'd ever imagine. I tested my own Trex Transcend composite decking.
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What was the Temperature of the Decking?
The temperature of my composite decking was 152.3 F. I measured it just after noon on August 10, 2018 using a FLIR thermal imaging camera attached to my smartphone. It was a cloudless day and the sunlight had been striking the decking for hours.
What is the Highest Temperature Composite Decking can Get?
I think the decking can get to over 160 F, or more, the closer you are to the summer solstice. The summer solstice is always on or about June 21st of each year. This is when the sun is highest in the sky and goes through the least amount of atmosphere.
Does Wood Decking Get as Hot as Composite Decking?
Yes, wood can get as hot. I measured a piece of 3/4-inch oak decking and it was the exact same temperature as the composite decking, 152.3 F!
The wider piece of wood is solid oak 3/4-inch thick. The narrow board is a treated lumber 2x4. They are suspended in the air to ensure the test is accurate because the composite decking below is exposed to air beneath the deck. Setting the pieces of wood directly on the composite decking would yield inaccurate results. Copyright 2018 Tim Carter
The crosshairs of the FLIR camera are on the oak as you can see. Note the temperature. I would have bet money it would have been cooler. Copyright 2018 Tim Carter
What is the Temperature of Treated Lumber?
The temperature of the treated lumber 2x4 was 138.2 F. That's just 14 degrees cooler than the composite decking.
You can see the FLIR crosshairs squarely on the middle of the treated lumber 2x4. It had been in the direct sunlight for hours. The temperature is 138.2 F. Copyright 2018, Tim Carter
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How about doing the asphalt driveway.
Great information. I've been selling composite decking since the beginning and the darker the color the hotter it gets. Didn't realize how close wood temperature is to composites. Thought they'd be a bigger difference.
I already experienced this when my shoes melted on our back deck, which faces the setting sun in evening. We live in the Southwest desert at high altitude. The paint I've applied to our decking and back doors has just blistered and peeled away. I don't know what might help, besides replacing the wood deck with Trex or using industrial grade epoxy on the doors so they won't blister. It doesn't look pretty, and the deck is unusable after it gets warm in the day. Perhaps building a large roof to give shade to the space is the fastest solution, because growing large enough trees will take many years.
Luckily the thermal conductance of wood is lower than something like ... tin roofs for instance.
I guessed 154 pretty close to your flir readings.
You do inspire me Tim. A story maybe just for you. I was a Plankowner (the first) teaching the electronics in the S3A Viking ASW aircraft('73). We had the entire aircraft simulated in an almost gym size room for training. One particular OinC doing 'dog & pony' demonstrations, had guests sit in a cushioned chair, get up, then an Instructor would scan it with the FLIR.
The OinC got the biggest kick out of the image, sometimes the sitters 'junk!'
I am interested in the temp of an Ipe deck?
Tim;
I can't help but wonder how much impact the two black wrought iron chairs had on the temperatures that you recorded. it seems likely that they would have reached an even higher temp, & would have passed it on to the two wood pieces. Still, I get the point of the testing, it pays to be aware of the impact that the sun has on much of our everyday items e.g., blacktop comes to mind...
I have an aluminum deck, while it may get hot it is not slippery because of the finish, and will NEVER need to be painted or replaced! We wear shoes when walking on it just like on a “worn” wooden deck would require due to splinters. We have no complaints wearing foot covers as the lack of maintenance required more than pays for the inconvenience of slipping on Crocs!
Many thanks for this interesting report.
I have a Trex deck and I will not step on in it without shoes.
Hi Tim, I am shocked at this but I believe it. I had a composite deck put on my house and thankfully it is on the north side of my house. I won't do it again but then I don't plan on having another deck built. Too many precautions for composite, like having to use the right shovel in the winter as not to ruin the composite. Thanks for the information.
There are paints with very high albedo and very high emissivity of infra red. If such a white paint can be tolerated aesthetically, the temperature can be reduced to the air temperature. Maybe a bleach to whiten the wood would also reduce the temperature.
I designed spacecraft that used white paint to keep cool 50 years ago.