How to Size Engineered Beams

Determine the type of load your beams will have to hold. This will depend on the use of the beams. For instance, if you are using an engineered beam as a roof support in New York, you will need to consider the potential live load of the snow and the roof's dead load. On the other hand, if you are using the engineered beam to support your home's first floor, you will need to estimate the maximum weight it will have to hold including people, appliances and furniture.

Determine the length you want your engineered beam to span. The longer the span of the beam, the more weight it will have to support. This will affect the width, depth and wood grade of your engineered beams.

Estimate the total load your beams will need to withstand. A good rule of thumb is that every foot of beam will support 15 pounds of dead load and 50 pounds of live load. So, a 10-foot beam will have to support around 650 pounds per linear foot.

Compare your measurements and specifications with a manufacturer's span table to determine which model, size and wood grade you need to use. For example, if you have a clear span of 16 feet for a floor support with a load of 450 to 650 pounds per linear foot of beam, you will need 5-12 by 12-3/8 inch engineered beams.