How Does a Wall Withstand Compression Forces?

Compressive Force

• Compression force occurs when two forces push opposite ends of a piece of material toward one another. For instance, think of the first floor wall of a house. The weight of all floors above this floor pushes down on the first floor wall from above. The Earth and the foundation of the home offer force from below. These two forces – one from above, one from below – compress the wall. Extreme compression forces can cause walls to barrel, buckle, crack of break completely.

Compressive Strength

• Compressive strength describes a material’s resistance to compression force. Builders, engineers and architects avoid problems due to compression force primarily by using wall material with the appropriate compressive strength for a job. Concrete, for instance, varies greatly in compressive strength. Before undertaking construction, builders test various types of concrete to find the one that meets or exceeds the needs of a job based on the expected compression force exerted on a wall. The compressive strength of a wood wall depends upon the type of wood used and the method of wood frame construction.

Measuring Compressive Strength in Concrete

• The compressive strength of concrete is measured in megapascals (MPa). Measuring the MPa value of concrete entails creating a block of material and placing it in a machine that exerts compression force until the concrete breaks. The strongest pressure the concrete can withstand before breaking constitutes its compressive strength measurement. MPa measurements for types of concrete usually range from about 17 to 70, though some types can reach upwards of 150. In terms of pounds of pressure per square inch (psi) resistance, 17 MPa equals a resistance of 2,500 psi, 70 MPa equals 10,000 psi and 150 MPa equates to about 21,755 psi.

Measuring Compressive Strength in Wood

• Compressive strength measurements in wood require a great deal more complex math than compressive strength measurements for concrete. Building a structure from wood requires cutting that wood into myriad small pieces and fitting them together. To measure the compressive strength of an actual wood wall, you must consider the type of wood used, the compressive strength of each wood beam and stud and potential weakening factors such as joints. Coatings on walls, such as stucco or concrete, also alter its compressive strength. All of this requires lots of advanced math. Contact an engineer or contractor for help with such calculations.

Weight Distribution

• Engineers and architects use weight distribution to help lessen the force exerted on a wall. Weight distribution does not help walls withstand compression force but rather redirects weight to lessen compression forces. In wood-framed houses, things like trusses and joist systems help relieve compression force by taking weight and moving it in multiple directions. Buildings with metal frames also sometimes use trusses. Large metal-framed buildings, such as skyscrapers, may contain weight support columns within the frame of the building so that not all weight is directed toward the walls.