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• THERMAL EXPANSION of MATERIALS - CONTENTS: What is the definition of coefficient of thermal expansion?How do building materials change in dimension in response to temperature changes, sun, shade, ice, snow?How do the dimensions of different building materials vary with temperature, heat, cold?Table of Coefficient of Expansion of Building Materials
• POST a QUESTION or READ FAQs about the thermal expansion or contraction of building materials as temperatures vary
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Thermal coefficient of expansion of building materials: here we provide a Table of Coefficient of Thermal Expansion of Building Materials - what is the linear expansion of glass, metal, wood, masonry or plastic in response to temperature changes.

We include a discussion of the definition of thermal coefficient of expansion, how thermal expansion causes trouble in building materials, and how to use the data in the thermal expansion table to calculate changes in material size as temperatures change.

## Table of Coefficients of Thermal Expansion of Common Building Materials

Sketch at page top and accompanying text are reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.

### Definition of the coefficient of thermal expansion

The linear expansion of a heated solid (or liquid) is measured by

α = the coefficient of linear expansion,

The coefficient of thermal expansion is defined such that α measures the percentage change in the length of the material per degree of temperature change. Be careful in comparing the coefficient of expansion of different materials from different reference sources for thermal expansion coefficients as various references quote α in degrees C, others in degrees F.

The following simple formula for the coefficient of thermal linear expansion in a building material is written to measure the percentage change in length per degree of temperature change:

α = (Change in Length / Original Length) / Change in Temperature

One can write similar formulas to calculate the coefficient of thermal expansion of a material in area (applicable, for example in thermal splitting of asphalt roof shingles ) or to calculate the coefficient of thermal expansion of volume. But because so many building material failures and leaks derive from cracks or openings due to thermal expansion of materials in length, that is our focus here.

Comparison of Coefficients of Linear Temperature Expansion of Common Building Materials
Name of Material
Coefficient of Temperature Expansion
Material Coefficient of Expansion in inches of expansion per inch of material per degree F. Material Coefficient of Expansion in inches of expansion per inch of material per degree F.
ABS plastic 0.0000170 (glass fiber-reinforced) Acrylic 0.0001300 (extruded)
ABS plastics 0.0000410 Polyethylene 0.0001110
Acrylic 0.0001300 (extruded) Polycarbonates 0.0000440
Acrylic 0.0000410 (sheet cast) ABS plastics 0.0000410
Aluminum 0.0000123 - 0.0000129 Acrylic 0.0000410 (sheet cast)
Brass 0.0000104 - 190 Epoxy 0.0000310
Brick 0.0000031 (brick masonry) Ice 0.0000280 (effects of freezing water)
Cast iron 0.0000058 ABS plastic 0.0000170 (glass fiber-reinforced)
Cast iron 0.0000060 (gray cast iron) Zinc 0.0000165
Cement 0.0000060 Lead 0.0000151
Clay tile 0.0000033 Aluminum 0.0000123 - 0.0000129
Concrete 0.0000080 (Concrete structure = 0.0000055) Brass 0.0000104 - 190
Copper 0.0000093 Copper 0.0000093
Epoxy 0.0000310 Concrete 0.0000080 (Concrete structure = 0.0000055)
Glass, hard 0.0000033 Iron, pure 0.0000067
Glass, plate 0.0000050 Steel 0.0000063 - 0.0000073 (also Iron, forged)
Glass, Pyrex 0.0000022 Cast iron 0.0000060 (gray cast iron)
Granite 0.0000044 (also Limestone, Marble) Cement 0.0000060
Ice 0.0000280 (effects of freezing water) Cast iron 0.0000058
Iron, pure 0.0000067 Glass, plate 0.0000050
Lead 0.0000151 Granite 0.0000044 (also Limestone, Marble)
Masonry 0.0000026 - 0.0000050 Nylon 0.00000447 (molding & extruding compound)
Mortar 0.0000041 - 0.0000075 Mortar 0.0000041 - 0.0000075
Nylon 0.0000447 (molding & extruding compound) Clay tile 0.0000033
Polycarbonates 0.0000440 Glass, hard 0.0000033
Polyethylene 0.0001110 Brick 0.0000031 (brick masonry)
Steel 0.0000063 - 0.0000073 (also Iron, forged) Wood,Oak 0.0000030 (across grain)
Wood,Oak 0.0000030 (across grain) Wood, Pine 0.0000028
Wood, Oak 0.0000027 (parallel to grain) Wood, Oak 0.0000027 (parallel to grain)
Wood, Pine 0.0000028 Masonry 0.0000026 - 0.0000050
Zinc 0.0000165 Glass, Pyrex 0.0000022

Readers can see from these building material coefficients of thermal expansion (also called coefficient of linear temperature expansion) that assembling a building component that uses multiple materials requires methods that allow for these differences in the degree of expansion as temperatures change. Failing to permit movement of abutting or connected building materials whose rate of thermal expansion varies significantly will lead to separation, cracks, leaks, or damage in many instances.

Examples of the problems caused by differences in thermal expansion of building materials are particularly seen in windows and skylights (
see SLOPED GLAZING DETAILS),

At SKYLIGHT LEAK DIAGNOSIS & REPAIR we include an example of failure of roof flashing cement that has lost its ability to tolerate thermal expansion and contraction on the building.

As we discuss at CRACKS in FIBERGLASS SHINGLES, we have not found a source defining the coefficient of thermal expansion of asphalt roof shingles
- CONTACT Us if you can provide that information.

### Reader Question: can thermal expansion of some building materials can lead to loud noises?

Can the high heat (100F today) cause a building material to expand/contract and cause a loud boom and vibration. - Angela 7/22/11

Interesting question, Angela; I can imagine that very hot metal roofing installed without allowance for expansion/contraction, or even a thin metal storage tank that is nearly empty could make a loud noise on being heated. But loud boom and vibration - if it is recurrent you'll be able to track down the noise to a source (let us know what you find as it may help other readers)

If the building was damaged by something else like structural movement you'd expect to see cracks or stuff out of plumb/square.

If the noise was due to a dangerous gas explosion (sewer gas or LP or natural gas) you need an expert on site immediately.

### Reader Question: I don't understand coefficients of thermal expansion

can we have the answers in plain english please?

Anonymous:

Sure, glad to oblige.

When you heat various substances, most of them expand, or get bigger.

The just how much bigger something gets is a function of the amount of temperature change and the properties of the specific material itself. Different materials expand at different rates.

Because the increase in size (thermal expansion) in a material can cause problems like breaks and cracking, especially where the material is bound tightly by something else, designers pay attention to the thermal expansion data of the materials involved.

The table above gives, for many substances found in or on buildings, the Coefficient of Expansion in inches of expansion per inch of material per degree F.

In plain english, the coefficient of expansion is the amount of increase in size of a given material for each degree Fahrenheit that its temperature increases.

Example: if the COE for pure copper is 0.0000093, that means that if we heat any specific volume of copper, say one cubic inch of copper, by one degree F, the copper will get bigger by 1 x 0.0000093. So our one cubic inch of copper would now occupy a slightly larger space = 1.0000093 cubic inches.

For an interesting example of how failure to allow for thermal expansion of materials causes trouble,
see THERMAL EXPANSION CRACKS in BRICK

or for a case that can cause a tank to rupture or a pressure/temperature relief valve to blow,
see THERMAL EXPANSION of HOT WATER.

#### Some Common Building & Material Failures We've Seen that Appear to Track to Thermal Expansion-Related Damage

• Cracked exterior brick veneer walls (built without an expansion joint)
• Cracked leaky metal roof valley flashing installed in too-long strips with no provision for thermal expansion
• Cracked automobile windshields that occurred not due to impact but when the vehicle was left in hot sun
• Cracked skylights or other building windows that were improperly constructed or installed, exposed to hot sunlight
• Cracked glass bowl used to heat substances in a microwave oven

Continue reading at THERMAL EXPANSION of HOT WATERor select a topic from the More Reading links shown below.

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