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Anatomy Of Home Siding – What You Need To Know

Part One: Thermal Expansion


>If you are even thinking about replacing the siding on your home, then you need to read this article. Far too often homeowners are sold on home siding they don’t want and they don’t need. Don’t waste your money on home siding that simply will not work on your home.

There are literally hundreds (if not thousands) of home siding products on the market today. From vinyl siding to fiber cement siding to everything in between. Just take a look at this comparison chart of various siding:

Now factor in styles and colors and you can see that your options are almost limitless.

We are going to focus on vinyl siding and fiber cement siding in this article because those are the two most popular types of home siding on the market today.


Home Siding – Thermal Expansion of Vinyl Siding vs. Fiber Cement Siding

Thermal expansion refers to the tendency of matter to change in shape, area and volume in direct response to changes in temperature.

So what does this have to do with siding? Everything.

Vinyl siding has one of the worst thermal expansion rates of any siding material on the market today. In fact, if exposed to direct sunlight at extreme temperatures, cheaper vinyl siding will actually warp…or melt.

In fact, Conventional PVC siding is typically only 0.040 to 0.050 in. thick and can be as thin as 0.038 in., so on top of easily warping, it also reveals any unevenness in the substrate, which can leave it looking flimsy.

But even worse is the expansion and contraction rate that occurs with vinyl siding when it is placed on your home. In fact, vinyl sidings rate of thermal expansion can be as high as about 0.3% to 0.4% for a 50º F temperature change.

This may not seem like much, but it becomes especially prevalent when you consider the type of weather we have here in Oregon. Really hot summers and long wet and cold winters cause multiple fluctuations – in other words all of the siding on your home will expand and contract at different rates.

Consider this. The expansion and contraction in vinyl siding is so severe that you cannot fasten vinyl siding directly onto your home for a weather tight seal. You must “hang” the siding on fasteners, through an expansion eyelet so that the vinyl siding can move as it expands or contracts.

Vinyl siding must be “hung” with eyelets in order to allow for the extensive expansion and contraction


This expansion and contraction is so bad, that many vinyl siding manufactures have been forced to redesign their products. That is why we are seeing so many new vinyl siding products entering the market – like foam backed siding or “composite” vinyl siding.

In short, if your vinyl siding is not installed EXACTLY RIGHT, you are not going to get a weather tight seals. Leaks will occur and that will lead to all sorts of problems.

Now compare that to Hardi-Plank, a fiber cement siding that is actually affixed in place providing you the absolute best seal against the elements.

This is why we firmly believe fiber cement siding is a better option. It allows for margin of error, has one of the lowest thermal expansion rates on the market and it is fastened directly onto your home providing a better seal against the elements.

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