Reuben's Home Inspection Blog


Don't Lean On Me - The 500 Pound Requirement For Guardrails

The International Residential Code requires deck guardrails to be present when the deck surface is more than 30″ above the ground.  Guardrails must be at least 36″ high, and must be designed in such a manner as to prevent 4″ sphere from passing through.  This is all pretty easy to build, as long as you own a tape measure.  The last requirement is that guardrails be able to withstand 200 pounds of pressure along the top rail.  Now here’s the kicker - according to some, the guardrail must also be constructed with a safety factor of 2.5.  

Click any of the photos of unsafe guardrails below for a blow-up.

Very wobbly (featured in video below), spacing greater than 4" Flimsy, spacing greater than 4" I don't even know where to start...Flimsy, less than 36" high, spacing greater than 4" Flimsy, spacing greater than 4"

A safety factor of 2.5 means that the guardrail must be constructed to withstand 500 pounds of pressure along the top rail.  This means that guardrails must be constructed to be ridiculously strong, and most methods of conventional contruction aren’t good enough.   A guardrail constructed with 4×4s attached to the deck with lag bolts will actually rip the bolts out of the deck long before 500 pounds of pressure can be applied to the top rail.

DTT2Z bracket made by Simpson Strong-TieThe easiest and surest way to construct a guardrail that will withstand 500 pounds of pressure is to use metal brackets that are designed just for this purpose.   A couple manufacturers that make brackets just for this purpose are DeckLok and Simpson Strong-Tie.   They’re also the ones that promote the safety factor of 2.5 (go figure).  According to reports that I’ve read by both of these manufacturers, metal brackets are the only way to achieve the 500 pound rating.  I’ve talked to deck builders that say there are other ways to achieve this rating, but I’ve never seen any testing reports that verify this.  Nevertheless, most building officials in the Twin Cities area aren’t picky about guardrail details, and they allow guardrails to be built without metal brackets.

To read an in-depth report with several different construction methods and tests, go here.  The only problem I have with this article is that the testing they’re doing is based on a single post, and no guardrail can ever be constructed with a single post.  As soon as other posts and right angles are incorporated in to the guardrail, it will get much stronger.  When I inspect houses and I find flimsy guardrails (like the one in this video), I tell my clients to repair or replace them.  When I find guardrails with 4×4s that have been notched, I tell my clients that the guardrail might not be strong enough to prevent a large, falling adult from breaking it.

Reuben Saltzman, Structure Tech Home Inspections - Email - Minnesota Deck Inspector

RELATED POST: Deck Safety (Balcony Collapse)


Reuben Saltzman, Structure Tech Home Inspections


Comment balloon 4 commentsReuben Saltzman • June 09 2009 06:34AM


Reuben, what is the recognized test for applying the 500 lbs?  Almost any weight going at the right speed will rip through the railing:)

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) about 11 years ago

Brackets and through bolts would be able to achieve the 200 lb. requirement. We have a Simpson rep here who gives great seminars on deck construction. The brackets he shows have been tested by Simpson and do meet the 200 lb. requirement. I have not heard of the 2.5 safety factor until now. Seems a bit excessive.

Posted by James Quarello, Connecticut Home Inspector (JRV Home Inspection Services, LLC) about 11 years ago

Charles - I'm not aware of any standard test.  Yes, any weight going at the right speed would destroy the railing, but that also means that it would be exerting more than 500 pounds of pressure.  In the testing that has been previously done, they used some kind of a winch to pull at the top of the post.

James - the brackets that Simpson Strong-Tie sells actually meet the 500 lb requirement.  I'm surprised they didn't mention this at the seminar you attended.  I first learned about this at a seminar given by Simpson back in November.  I couldn't believe how much stuff I had been missing on decks.... how about you?

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) about 11 years ago

No doubt the Simpson seminars are full of great info. I always pick up some new and useful tips for my inspections. I'll have ask about that 500 lb. limit next time I see the rep.

Posted by James Quarello, Connecticut Home Inspector (JRV Home Inspection Services, LLC) about 11 years ago