How do you size a load bearing beam?

Load Bearing Beam Sizing

The first thing to understand is that there are two types of beams: Loadbearing and Shear bearing. A shear bearing consists of several pieces connected together at right angles. These pieces will not move with each other due to their angle, but they will still cause the whole structure to sway when one piece fails or breaks.

A load bearing beam consists of only one solid piece connected at right angles. The weight of the entire structure does not cause any movement. If one piece fails, then all other pieces remain intact.

In order to determine which type of beam you have, you must measure the width between your top edge and bottom edge (also called “peak” or “peak to trough”). You may use a tape measure or simply look at it from different sides. If the peak is wider than the trough, then it is a shear bearing. If the peak is narrower than the trough, then it is a load bearing.

If you are unsure if your beam is a shear or a load bearing, then you should measure both ends of your beam. The difference between these measurements will give you an idea of whether it is a shear or a load bearing.

How Do I Size My Load Bearing Beam?

To determine how much material to buy for your load bearing beam, divide its height by 2. For example: a beam that is 8 feet high would need 4 feet of material. Beams longer than 12 feet should be made with a steel box, or “header”, to reinforce the top of the beam. This is especially true if the distance between the support posts are greater than 8 feet.

You are now ready to build your beam. You will need some heavy planks. Ideally, you will use 2″x12″ or 2″x10″.

Sources & references used in this article: