The following table provides the coefficients of linear thermal expansion and representative thermal expansion values for various building materials. Where possible, the values were taken directly from manufacturer technical data sheets and reflect the coefficients of linear thermal expansion for specific, representative products. In a few cases, the values we give were calculated by averaging manufacturer or producer data from more than one source, or were taken from a non-commercial source that we consider authoritative.
We discuss thermal expansion here, but everything applies in reverse as the temperature decreases and the material contracts.
The coefficient of linear thermal expansion (CLTE) is the change in the length of a quantity of material as a fraction of the original length of the material per degree of temperature change. So when you see a manufacturer’s technical data sheet express the CLTE as “in/in•°F” (or very often as “in/in/°F”), you can read that as “change in length (measured in inches) per inch per degree.
If the CLTE is one millionth of an inch, that means that for every degree of temperature increase, one inch of the material will expand to be 1.000001 inches long. For a ten foot long section of material (120 inches), that means an increase of 120 millionths of an inch for a one degree change. For a 100 degree increase, that means the original ten foot section will add 12,000 millionths of an inch to its length. The original ten foot section will now be 10 feet and 0.012 inches long. (One millionth of an inch is not a typical CLTE, all of the materials listed below have much larger CLTE’s.)
Please note that variations in product formulations, the manufacturing process, and the temperature range can all affect actual thermal expansion values. Built-up roof membranes, for instance, have much larger CLTE’s from -20°F to +30°F than they do from +80°F to +130°F. The CLTE of concrete varies according to the type of aggregate material used in the mix. The roofing membrane materials listed below will typically develop smaller CLTE’s as they age.
These thermal expansion values are meant to provide a general idea of how much various materials expand and contract due to temperature change, and should not be used if precise values are needed for critical engineering calculations. When precision is necessary, always refer to the data sheets of the actual, specific product you intend to use. If the data sheets do not provide a coefficient of linear thermal expansion, contact the technical department of the product manufacturer or material provider.