Why does my composite deck make loud 'cracking' sounds in the winter?

Answered by Brendan ~ February 16, 2010 ~ Comments

I don't know the brand of decking as we just bought the house and this is our first winter here. The composite material used in our deck makes loud cracking sounds, like a rifle shot, when the temp is below zero. This happens with no set frequency - sometimes twice an hour for a few hours, or maybe not at all for a whole day. What is causing this, and more importantly, is this affecting the soundness of the deck? What can we do to fix this? Thank you!

Pat ~ Norfolk, Nebraska

Brendan Fowler

Let me start by saying that composite decking and wood have different expansion coefficients. This means that they move differently in changing temperatures. I can not say for sure what is causing the cracking sounds, but I can give you a couple of scenarios that might be a cause.

If you are going through a freeze thaw cycle every day, there may be a situation where the water trapped between the composite deck board and the wood joist freezes and forms a glue like joint that breaks at certain temperatures.

The same thing can happen if during the day the temp is high enough for the boards to expand and get so close together that as the temperature drops the boards freeze edge to edge. As the temperature drops further, the deck boards shrink, causing the ice glue joint between the boards to fail, thus causing a popping noise. All of the noise is probably not effecting the structural integrity of the deck. I have had situations in high alpine environments where the freeze thaw cycle was enough to shear off deck screws in composite decking. I would check all of the screws during warmer weather to make sure that none of the screws have sheared during the winter months.

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