Weight Limits For Load Bearing Studs...

StudioDan

I put up a shed supported by 4x4 posts and noticed a good amount of vertical cracking in the supports. At first this scared me as I thought maybe I had too much weight and these were stress cracks. But then I got to looking at some various decks, fences even went to the lumber yard and noticed the same type cracks in all the dried 4x4s I found.

This still got me thinking tho... How much load can a vertical 4x4 support?

KentWhitten

alot. those cracks are normal. it's when they're horizontal is when you start getting nervous.

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StudioDan

What I figured if the weight is distributed evenly is that each 4x4 post is supporting a max of about 420 pounds.

Thats about 3 of me and I cant imagine that weight being a threat to a vertical 4x4... even a horizontal one with a decent span.

reveivl

A 4x4 in good condition, if held in a vertical position, can take thousands of pounds of pressure. The cracks you're seeing are likely just drying checks.

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StudioDan

Thanks for the reassurance.

RobertCDF

It is roughly 4,300 LBS for the entire post. This can vary by species but they can support a lot of weight.

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Colorado Springs Custom Decks
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EasTnBldr

Although "varying by specie" is VERY true and something to be considered when you get outside the "norm" of standard framing material ... the rule of thumb would be 500lbs. per square inch of material = end grain carrying capacity. Thus a 3 1/2" x 3 1/2" piece of material is 12.25 sq. inches of material = 6,125 lbs. of end grain support. I would use this number up till the point that member reached 8' of vertical hold without diagonal bracing. If the 4x4 were used in a shed with rated sheathing on the exterior wall ... the original number will hold.

As far as the "cracking" that you see ... it's called "checking." Very common in all materials 3" thick or thicker. I do a lot of post and beam construction and it's one of my many headaches trying to explain to HOs that have exposed beams and see this happen. I've had them ask "how do you fix it" ... my general response is "that's wood ... that's what it does ... and quite frankly, those that truly "love" wood ... enjoy every bit of character it adds ... speaking of character ... I threw that in for free." Most times they just laugh and understand.

EasTnBldr

As an additional thought ... it's better to work with the number given prior to my last post. Maxing out a pc. of lumber's capacity is never a good course of action. Yes, it might hold ... but you never know when you get that one piece that slipped thru the "graders" eye-sight. It may be stamped #1, #2, or #3 & btr. but that doesn't always mean that it is.

RobertCDF

This number came from my building department and is probably based upon worst case situations (lowest grade lumber, cracks that do affect structural load ratings, blah blah blah) (I think they use 375 lbs per sq in.) It is never wrong to upgrade before really needed... In this case I dont see a point in worrying about the posts in the shed.

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Robert Shaw
Colorado Springs Custom Decks
Colorado Custom Decks
Custom Composite Decks