## How do I calculate load bearing capacity of lumber?

## How do I calculate load bearing capacity of lumber?

(OP)

We have a stand alone office in our warehouse. I need to calculate load bearing capacity (PSF)of the roof. The roof is constructed of 2x6 joists on 24" c/c, 11'6" span, 9'4" wide, with a 3/4" plywood sheeting on top. We also have a forklift manlift basket 48" x 48" x 50" high, constructed of 1.25 x 1.25 x 18 SQ Tubing I need to calculate a load capacity for that aswell. Thanks for any help.

## RE: How do I calculate load bearing capacity of lumber?

Usually, this is a requirement of insurance companies in industrial settings and usually they require a signed and sealed letter from a licensed structural engineer. You are asking for engineering services (not tips) on this site.

I would suggest you hire a structural engineer to fully determine the capacity of this roof and the basket as the data that you could provide on this site wouldn't provide all the information needed to fully calculate the capacity, or understand all the parameters, of this problem.

## RE: How do I calculate load bearing capacity of lumber?

For example, how can we determine the load capacity of a manlift basket if we don't even know anything about the manlift itself?

## RE: How do I calculate load bearing capacity of lumber?

## RE: How do I calculate load bearing capacity of lumber?

## RE: How do I calculate load bearing capacity of lumber?

Another method is to determine how much weight a 2 x 6 at 24" O.C. over a span of 11.5' is allowed to support in PSF. In order to answer this question, need to know the species and grade (visually or machine graded) of the wood, or one has to assume a low grade and low strength species. I would use the National Design Specification for Wood Construction to answer this question. Would need to check to see what governs the strenth--is it the joists, the joist connections, the plywood sheathing, etc.

## RE: How do I calculate load bearing capacity of lumber?

....plywood sheathing, support beam capacities, support wall (stud) capacities, lateral stability of the office, code compliance issues (guardrail, stair, etc.), joist shear capacity, etc.

There isn't a "formula" that serves to replace the appropriate practice of engineering.

## RE: How do I calculate load bearing capacity of lumber?

If you're trying to find out if you can add more weight to the roof, such as roof equipment, then you're back to checking ALL the members and connections in its load path down to the foundation for adequacy.

## RE: How do I calculate load bearing capacity of lumber?

I would check all the failure modes, e.g. shear, bending, delfection, axial, interaction of axial and bending, headers, jambs, connections, etc. and the load capacity will reveal itself in your results. Try to base that on the in situ conditions as much as possible also since you don't know that the builder followed the plans, if you even have plans to look at.

I think you should hire someone, pay him or her the couple hundred dollars to write you a signed and sealed letter telling you what you need to know and go home and sleep well at night.

## RE: How do I calculate load bearing capacity of lumber?

## RE: How do I calculate load bearing capacity of lumber?

I may be wrong but it sounds like someone wants to store some materials on the roof of this office enclosure (shed?)which is INSIDE an existing warehouse building. Very risky. Many unknowns. Must be seen. I'd be surprised if anyone ever really engineered the office before it was built. This office may be nothing more than partition walls with a light duty roof to retain heat and air conditioning and to block out noise and dust. Sorry, gbabob.

## RE: How do I calculate load bearing capacity of lumber?