How to Size a Vertical Support for a Level Horizontal Beam

Measure the length of the horizontal beam that you will be supporting. If you're installing a support beam for a beam in a load-bearing wall, you will have to measure the length of the wall rather than the beam itself.

Determine the length that the vertical support beam will need to be by measuring the distance from the ground or floor to the bottom size of the horizontal support beam. This will be simplest part of the task of sizing your beam. The length of the vertical beam will help determine the size of the beam that you should pick.

Examine the load size that the beam will be supporting. For example, a support beam for a wooden deck is likely to need less thickness than one that is supporting a load-bearing beam in a wall. Generally, a 4-by-4 vertical support beam will suffice for most types of jobs. However, for jobs where you will be supporting a much larger workload, you will need to choosing a thicker piece of lumber, such as 4-by-6 or even a 6-by-6.

Choose a beam thickness based on the length of the of the beam. Beams up to 8 feet long can use beams as narrow as a 3-by-8 piece of lumber. Beams up to 10 feet long will be better with a 4-by-8 piece of lumber. Even larger sizes are typically used for spans between 10 and 12 feet. Beams can be anywhere from 3-by-10 to 4-by-12.

Consult a structural engineer before making any changes to load-bearing walls. Consult local building codes and get professional advice before proceeding with any major renovations.