New Loads on Existing Structures

By Brian Ki, P.E. | July 7, 2021

We often have clients and contractors wishing to modify an existing building to create some sort of new space. In these types of projects, an assessment of the existing structure is necessary to see what is structurally feasible.  Often, the loads of the building must be redesigned and redistributed.

There is common misconception when existing engineered wood (LVL’s, PSL’s, etc.) or steel beams are discovered. These elements are much stronger than conventional lumber and many contractors ask, “can’t we just post down to those types of materials without having to improve them?” The answer is almost always no.

The reasoning of a really strong material being able to carry a hefty load does not provide an accurate account of what goes on during the design process. Engineers will design structures to meet the requirements of the code, that’s the line set in the sand. Anything under is considered unsafe and could cause structural failure. Anything over is conservative, usually adds unnecessary costs to the project, and the person paying typically does not appreciates it.

Put into context, existing structural members usually can withstand the loads for when the building was originally designed, and not necessarily additional loads that a new renovation often calls for.

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