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  1. #1
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    Default Guard opening limitations explanation

    Can someone please remind me what this means, in the 2006 IRC:

    "Guards: R312.2 - Exceptions: Openings for required guards on the sides of stair treads shall not allow a sphere 4 3/8 inches to pass through."

    I'm having trouble visualizing the difference between "guards on the sides of stair treads" and "Required guards on open sides of stairways..."

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    Default Re: Guard opening limitations explanation

    Quote Originally Posted by John Arnold View Post
    Can someone please remind me what this means, in the 2006 IRC:

    "Guards: R312.2 - Exceptions: Openings for required guards on the sides of stair treads shall not allow a sphere 4 3/8 inches to pass through."

    I'm having trouble visualizing the difference between "guards on the sides of stair treads" and "Required guards on open sides of stairways..."
    John,

    This is what you are referring to:
    - R312.2 Guard opening limitations. Required guards on open sides of stairways, raised floor areas, balconies and porches shall have intermediate rails or ornamental closures which do not allow passage of a sphere 4 inches (102 mm) or more in diameter.
    - - Exceptions:
    - - - 1. The triangular openings formed by the riser, tread and bottom rail of a guard at the open side of a stairway are permitted to be of such a size that a sphere 6 inches (152 mm) cannot pass through.
    - - - 2. Openings for required guards on the sides of stair treads shall not allow a sphere 4
    3/8 inches (107 mm) to pass through.

    You took part of that out of context and then it did not make sense: (read it this way)
    Required guards on
    - open sides of stairways,
    - raised floor areas,
    - balconies
    - and porches
    - shall have intermediate rails or ornamental closures which do not allow passage of a sphere 4 inches (102mm) or more in diameter

    ALL of the above shall have openings which shall not permit the passage of a 4 inch sphere ... well, except for ...

    ... okay, there is an exception to the on "open sides of stairways":
    - - - 2. Openings for required guards on the sides of stair treads shall not allow a sphere 4 3/8 inches (107 mm) to pass through.

    Which means that guards on the open sides of stairs are allowed to have openings through which a 4 inch sphere CAN pass, just not a 4-3/8 inch sphere.

    Got it?


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    Default Re: Guard opening limitations explanation

    Anyone care to guess or explain why the exception is in there?


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    Default Re: Guard opening limitations explanation

    JP - I don't get it, no. Not trying to be dense. It just comes naturally.

    What I'm not getting is the difference between
    "open sides of stairways" and
    "
    on the sides of stair treads".

    Can you describe to me in, other words, where it is ok for a 4" sphere (but not 4 3/8") to pass?

    Thanks.


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    Default Re: Guard opening limitations explanation

    I think "open sides of stairways" is referring to the landing between stairs. and
    "
    on the sides of stair treads" is on the stairs themselves.


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    Default Re: Guard opening limitations explanation

    Quote Originally Posted by neal lewis View Post
    Anyone care to guess or explain why the exception is in there?
    I believe it has to do with the length of the standard tread on a stair.


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    Default Re: Guard opening limitations explanation

    Quote Originally Posted by John Arnold View Post
    Can you describe to me in, other words, where it is ok for a 4" sphere (but not 4 3/8") to pass?
    The 4" applies to landings, balconies, decks, etc.

    The 4-3/8" applies to the flights of stairs, i.e., where the treads and risers are, the angled portion of the stair. I.e., you could have 4-3/8" at a flight of stairs, 4" at the intermediate landing, 4-3/8" at the next flight of stairs, then end with 4" at an upper balcony/loft/bridge at the second floor.

    Make sense?

    Not to me either.

    What about the 6" sphere at the triangular area of the tread/riser/guard with a bottom rail? Some how the 6" is not supposed to be dangerous there, but over 4-3/8" is at the guard above that 6" opening. Has more to do with no affecting constructibility than safety if you ask me ... to avoid the 6" triangular area the balusters would need to go all the way to the tread and no bottom rail would be allowed - this would reduce the choices available for design of the guard.

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    Default Re: Guard opening limitations explanation

    Jerry - Thanks.

    No, it doesn't make sense to me, either, and now I realize that's what was confusing me!

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    Default Re: Guard opening limitations explanation

    Quote Originally Posted by John Arnold View Post
    Can someone please remind me what this means, in the 2006 IRC:

    "Guards: R312.2 - Exceptions: Openings for required guards on the sides of stair treads shall not allow a sphere 4 3/8 inches to pass through."

    I'm having trouble visualizing the difference between "guards on the sides of stair treads" and "Required guards on open sides of stairways..."


    This might help....

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    Default Re: Guard opening limitations explanation

    The 4-3/8 inch spacing on the stair treads came about due to the depth of the tread 7-3/4 inches. Itís about the math guys. Two diagrams that should help.

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    Wink Re: Guard opening limitations explanation

    This one is for California inspectors as of Jan. 1, 2011.
    (Just think, more love from our agent friends!)

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    Default Re: Guard opening limitations explanation

    Quote Originally Posted by Jerry McCarthy View Post
    The 4-3/8 inch spacing on the stair treads came about due to the depth of the tread 7-3/4 inches. Itís about the math guys. Two diagrams that should help.


    Riser maximum height 7-3/4"

    Depth of Tread - minimum 10" clear w/nosing projection, 11" min w/o.

    Which math allows a legal stair witha 7-3/4" deep tread, and where is this shown in your attachments?

    I admit EW/ WC Jerry, I'm not picking up what you're putting down.
    I'm confused by your post.


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    Default Re: Guard opening limitations explanation

    Sorry, I miss-spoke as I meant 10 inch tread rather than a 7-3/4 inch riser.
    Haste makes waste.

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    Default Re: Guard opening limitations explanation

    Okay, but I still don't see the point of where it is in the math as you said.
    The same 3/8" slop factor or larger more permissive sphere size exception holds for open sides of stairway guards which have a bottom rail or which land upon a solid sloped plane.

    The older rules (when risers could be taller) had larger sphere tests for the guards (wider spacing).

    To the questions earlier posed:

    There is no difference, it is the same open side of stairways that's being referred to in both the subsection and the exception.

    It is how the code is written, first an all inclusive most restrictive (not pass a 4" sphere) overall statement regarding all such guards, which includes the guards on open sides of stairways; followed by a set of exceptions which are less restrictive that is to say more permissive for the guards at open sides of stairways (i.e. the 6" sphere under bottom rail on open sides of stairways, and the 4-3/8" sphere between ballisters/guard vertical guard componants on open sides of stairways).

    Why the 3/8" difference, or more permissive (4-3/8" sphere not to pass instead of smaller 4" sphere not to pass) or a 3/8" greater allowance, larger sphere on open sides of stairways?

    3/8" is the overall maximum slop-varience permitted in the IRC staircode for interior stairways' treads, nosings, and riser heights.. 3/8" max. overall nosing var., 3/8" max. overall tread depth var., 3/8" max. overall riser height var. - all which effect rise and run; therefore 3/8" is also the max overall ballister/guard max. varience.

    Why would you need? Even if using perfect non-turned ballisters - you may have visually off-set tread depth/riser height slop to make up for.
    turned guards will be offset at some point in the overall guard, from tread to tread or overall if captured on bottom rail.

    If you've a varience on one axis you can only correct with the other, after its built (the stairway). Its not a chicken or the egg question, the stairway comes first, the guard follows.

    You've got three planes and the complication of larger openings, and turnings - even if you're within 1/8" on each - you're covered with the not-to-let the 3/8" larger diameter sphere pass.

    Generally in site built stair you design/plan to 4" as tight as tolerance as is reasonable with finish carpentry a 1/10 - 1/20" is about as tight as you can affect individually with ideal conditions with power tools in the field considering its wood we're talking about; 1/8" is about as tight as you can expect overall with a very careful craftsman even if goaling for tighter. The 3/8" is the max overall tolerance for the entirety. You usually also have wood products in a vertical orientation, which as they age, tend to shrink some overall, may twist a bit as they age, and have seasonal shifts in less than ideal conditioned environments, as will likely, the overall stairway.

    Last edited by H.G. Watson, Sr.; 01-14-2011 at 09:03 PM.

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    Default Re: Guard opening limitations explanation

    Hal, I looked you up and found you're far more educated than I am, therefore I will defer to all things mechaical in which you offer an opinion on. In no way am I being sacastic, but would like to remind you there is a difference between wisdom and knowledge.

    Some day I'd like to hear you expand on your Mini-Mag-Light legal case if you can. Professor Watson is all he says folks so listen to him and learn. I close with an age old definition of engineering;

    Definition: Engineering
    ďThe art and science of molding materials we do not fully understand; into shapes we cannot precisely analyze; to resist forces we cannot accurately predict; all in such a manner that society at large is given no reason to suspect the extent of our ignorance."

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    Default Re: Guard opening limitations explanation

    Quote Originally Posted by Jerry McCarthy View Post
    Hal, I looked you up and found you're far more educated than I am, therefore I will defer to all things mechaical in which you offer an opinion on. In no way am I being sacastic, but would like to remind you there is a difference between wisdom and knowledge.

    Some day I'd like to hear you expand on your Mini-Mag-Light legal case if you can. Professor Watson is all he says folks so listen to him and learn. I close with an age old definition of engineering;

    Definition: Engineering
    ďThe art and science of molding materials we do not fully understand; into shapes we cannot precisely analyze; to resist forces we cannot accurately predict; all in such a manner that society at large is given no reason to suspect the extent of our ignorance."
    While our H.G. is very intelligent, and I appreciate his presence on this forum, the CURRICULUM VITAE OF HAL WATSON, JR. Ph.D., P.E., makes no mention of either MI or Fl. I believe we are still looking to find "who is H.G. Watson Sr.?" JMHO


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    Default Re: Guard opening limitations explanation

    Vern

    I sure hope that the Dr. Watson on this BB is who he says he is and not a fraud otherwise many of us will be devastated. Perhaps we should contact Sherlock for confirmation?


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    Default Re: Guard opening limitations explanation

    Quote Originally Posted by Jerry McCarthy View Post
    Vern

    I sure hope that the Dr. Watson on this BB is who he says he is and not a fraud otherwise many of us will be devastated. Perhaps we should contact Sherlock for confirmation?
    But he has never said who he is, other than H.G. Watson Sr., which the CV lists as a Jr. Not that it matters to me. I appreciate the posts whom ever he is.

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    Default Re: Guard opening limitations explanation

    Very interesting brethren.

    I appreciate Watson's thinking.

    I always assumed the exception was a "break" granted to builders who use turned balusters where distances between are subject to variation.

    I have known carpenters who were practically hairless trying to arrange turned balusters to meet req., especially ones where the only way to get it is by having three per tread, which looks like the devil.


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    Default Re: Guard opening limitations explanation

    It's quite explainable and simple to understand. Because of the tread width requirement, on an open stair and attaching spindles to the treads, you would need 3 spindles per tread, which would make for a fairly odd looking railing in my opinion. Your spacing would be around 2". That's why the extra 3/8" allowance of spacing.

    On the 6" sphere, because it's a triangle, it would be most difficult for someone to fit through the opening.

    There really would be no other way to comply with the code, this would render these two methods of construction non-compliant. I don't believe these methods are really any more dangerous than other methods.

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    Default Re: Guard opening limitations explanation

    Thanks Jin and Door Guy. I rest my case.

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    Default Re: Guard opening limitations explanation

    Perhaps if you begin reading the section R312 @ R312.1 and read all the way through you wouldn't have a question. Not to minimize your question but I have no problem with the interpretation. Have a great day.


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    Default Re: Guard opening limitations explanation

    Here's the best document I have found for information on stairs and gaurds in the IRC.

    http://smai.roundtablelive.org/Resou...20download.pdf


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    Default Re: Guard opening limitations explanation

    Quote Originally Posted by Door Guy View Post
    It's quite explainable and simple to understand. Because of the tread width requirement, on an open stair and attaching spindles to the treads, you would need 3 spindles per tread, which would make for a fairly odd looking railing in my opinion. Your spacing would be around 2". That's why the extra 3/8" allowance of spacing.
    In South Florida, for decades we used the 4" for stairs too, and, yes, they install 3 balusters per tread, and, no, it did not look "fairly odd", it in fact looked "normal".

    On the 6" sphere, because it's a triangle, it would be most difficult for someone to fit through the opening.
    Let me get this straight ... ... a 6" sphere is a triangle?

    A person is not going through an opening (there are not prohibited shape requirements for guard openings) which is a 4" diameter circle any easier than they would go through a 6" diameter circle opening ... no way can you convince me that a smaller opening is less safe than a larger opening, and whether or not the opening is "triangular shaped" or "odd shaped", the key is the dimension which would allow a spherical object to pass through, and a larger 6" diameter opening will more easily allow an object to pass through than a smaller 4" diameter opening will.

    Convince me otherwise.

    There really would be no other way to comply with the code, this would render these two methods of construction non-compliant. I don't believe these methods are really any more dangerous than other methods.
    Not sure what that means or is referring to - if the code limited the opening size to 2" then construction would comply with that. The code limits the opening size to 4", 4-3/8", and 6", and if the two larger openings are "safe" then when not make them all 6", unless 6" is not safe, in which case make them all 4" ... makes no sense to me, and I have been trying to allow myself to be convinced that somehow the 6" opening is based on the same research (or better research) that the 4" opening is based on - but I still don't understand it. I *do* understand why the opening in the IBC (non-residential) allows a maximum of a 4" diameter sphere to a height of 34" and an opening of 8" from a height of 34" and higher as a taller child would have a larger head, but ... that flies in the face of the 6" allowed for the triangular opening down low ...

    I have always been told that was a compromise to allow more design flexibility for architects and designers as restricting the 6" opening to a 4" opening would virtually prohibit guards with bottom rails and require guards with balusters from the tread up the the top rail, which would also greatly increase the cost of the guard rail (it would as it is quick and cheap to manufacture a guard with a top and bottom rail, then install it between a support at the top and bottom of each flight of stairs).

    The same reason was given for the 4-3/8" openings for guards on the sides of stairs - only requires two balusters instead of three ... again, money, not safety.

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    Default Re: Guard opening limitations explanation

    It's always been about the money. BTW, I understand the 4" diameter sphere rule as far as an opening 4" or more 36" in height (in CA 42"), or an open riser regarding an infant slipping through it, but cannot envision them squeezing through 6" triangular opening between a baluster and riser.

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    Default Re: Guard opening limitations explanation

    Quote Originally Posted by Jerry McCarthy View Post
    but cannot envision them squeezing through 6" triangular opening between a baluster and riser.
    It's not a " 6" triangular opening ", it is a triangular opening large enough to pass a 6" sphere, which means it is much larger than that 4" opening, in fact ... ... it is more than 2" larger than that 4" opening in its smallest dimension of the sphere space.

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    Default Re: Guard opening limitations explanation

    Quote Originally Posted by Door Guy View Post
    It's quite explainable and simple to understand. Because of the tread width requirement, on an open stair and attaching spindles to the treads, you would need 3 spindles per tread, which would make for a fairly odd looking railing in my opinion. Your spacing would be around 2". That's why the extra 3/8" allowance of spacing.

    On the 6" sphere, because it's a triangle, it would be most difficult for someone to fit through the opening.

    There really would be no other way to comply with the code, this would render these two methods of construction non-compliant. I don't believe these methods are really any more dangerous than other methods.
    In Canada we don't have the extra 3/8". 4" everywhere. I built a set of stairs last fall which came very close to the limit. I laid out the spindles and used the 4" rule to determine the unit run of the stairs. The extra 3/8" would be nice. (I think I would find 3 spindles per tread looking cluttered but maybe that is just because I'm not used to it.)


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    Default Re: Guard opening limitations explanation

    Quote Originally Posted by Jerry Peck View Post
    In South Florida, for decades we used the 4" for stairs too, and, yes, they install 3 balusters per tread, and, no, it did not look "fairly odd", it in fact looked "normal".



    Let me get this straight ... ... a 6" sphere is a triangle?

    A person is not going through an opening (there are not prohibited shape requirements for guard openings) which is a 4" diameter circle any easier than they would go through a 6" diameter circle opening ... no way can you convince me that a smaller opening is less safe than a larger opening, and whether or not the opening is "triangular shaped" or "odd shaped", the key is the dimension which would allow a spherical object to pass through, and a larger 6" diameter opening will more easily allow an object to pass through than a smaller 4" diameter opening will.

    Convince me otherwise.



    Not sure what that means or is referring to - if the code limited the opening size to 2" then construction would comply with that. The code limits the opening size to 4", 4-3/8", and 6", and if the two larger openings are "safe" then when not make them all 6", unless 6" is not safe, in which case make them all 4" ... makes no sense to me, and I have been trying to allow myself to be convinced that somehow the 6" opening is based on the same research (or better research) that the 4" opening is based on - but I still don't understand it. I *do* understand why the opening in the IBC (non-residential) allows a maximum of a 4" diameter sphere to a height of 34" and an opening of 8" from a height of 34" and higher as a taller child would have a larger head, but ... that flies in the face of the 6" allowed for the triangular opening down low ...

    I have always been told that was a compromise to allow more design flexibility for architects and designers as restricting the 6" opening to a 4" opening would virtually prohibit guards with bottom rails and require guards with balusters from the tread up the the top rail, which would also greatly increase the cost of the guard rail (it would as it is quick and cheap to manufacture a guard with a top and bottom rail, then install it between a support at the top and bottom of each flight of stairs).

    The same reason was given for the 4-3/8" openings for guards on the sides of stairs - only requires two balusters instead of three ... again, money, not safety.
    Jerry, first you know what was meant by the 6" sphere being a triangle, and so did everyone else.

    I really shouldn't need to convince you... I'm very sure your good at math. A run of 11" and a rise of 7" triangle yeilds a 38.5 sq. inches (.26 sq ft.) of space that a 6" sphere will not fit through.

    A 4" by 36" space between a spindle yields a 144 sq. inches (1 sq ft.) of opening. Which one sounds bigger now? The 4" spindle spacing yields almost 4 times the area than the 6" sphere requirement.

    Most humans only have one part of there body that is a sphere, their head (except Santa Claus, he pretty round). I have never met a human that only has a head and no body. I also have never seen someone who's shoulders are smaller than their head.

    While sideways shoulders may be narrower than a head, this is why the prior 6" spacing was changed to 4". Small children with a head smaller than 6" could get their shoulders through sideways. There is no way to turn sideways to slip through a trianglar opening. Especially one that is 4 times smaller in area than allowed on upright spindles.

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    Default Re: Guard opening limitations explanation

    Door Guy nailed it. These 2 diagrams may help understand this particular code?

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    Default Re: Guard opening limitations explanation

    Quote Originally Posted by Door Guy View Post
    Jerry, first you know what was meant by the 6" sphere being a triangle, and so did everyone else.
    Apparently you do not, not based on the below statement by you ...

    A 4" by 36" space between a spindle yields a 144 sq. inches (1 sq ft.) of opening. Which one sounds bigger now? The 4" spindle spacing yields almost 4 times the area than the 6" sphere requirement.
    You have apparently missed a very key word ... "sphere" ... not "circle" or "circular area" - "sphere".

    The concern is IN NO WAY RELATED TO the "area of the opening", the concern is related to the "dimension" of the opening", i.e., you could have a decorative pattern which included staggered 3.9375" (3-15/16") square openings which had an area of 15.5 square inches, or a decorative pattern which included staggered 3.9375" (3-15/16") circles which had an area of 12.2 square inches ... BOTH would NOT allow a 4" sphere to pass (provided, of course, that the material was strong enough to resist deforming and becoming enlarged) and thus BOTH would be acceptable, even though the square pattern clearly is larger than the circular pattern.

    I.e., it does not matter that a 3.9375" opening is 0.5" in the other direction or 53" in the other direction - the key is that the 3.9375" dimension will not allow a 4" sphere to pass through.

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    Default Re: Guard opening limitations explanation

    Quote Originally Posted by Jerry McCarthy View Post
    Door Guy nailed it. These 2 diagrams may help understand this particular code?
    The Door Guy missed it entirely, he is thinking area and not single dimensional size - the space could be 100 feet long as long as it does not pass a 4" sphere in the other dimension.

    My drawing shows the space at the tread-riser-railing bottom triangle and that it is larger than the 4" opening for the guard.

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    Default Re: Guard opening limitations explanation

    We all know a 4" sphere is smaller than a 6" sphere. What is critical is the shape of the opening. A triangle that progressively gets narrow at each end is much harder for a person to slip through. That's the point here. NOT which is bigger a 4" or 6" hole. Clearly most code officials agree or it wouldn't be in the code. I don't believe this is money issue either. Neither section is more or less safe.

    We are worried about this code section being safe. Take a look at this link of the Mackinaw Bridge. Thousands have walked this bridge, take a peek at the guard rail here... a little larger than 4".

    Mackinac Bridge

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    Default Re: Guard opening limitations explanation

    Bottom rails for stairway guards, do not always run directly OVER, along or nearly upon the nosing of exposed treads on stairs!!

    In fact most DO NOT.

    An open stairway can still have captured treads!

    A stairway does NOT require solid, full-height captured risers. An open stairway may well have minimally guarded, otherwise open risers.

    Openings beneath stairway guard bottom rail (s) can be in shapes other than simple triangles!

    That is the area the 6" sphere-not-to-pass rule is applied.

    Get out of the "triangle" thinking box. Even as pictured the area opening is NOT simply a triangle, nor is the opening area simply 2-dimensional! Skip the "largest circle" (and the term is incircle) "that can fit in a right triangle" crud.

    The sphere is allowed to roll, rotate and change orientation. If (a sphere, a six inch sphere, not a circle) it does and can pass through ANY (Three-dimensional!) opening between the stair (not necessarily the tread) and the lower or bottom guard rail the stairway guard test for area below the bottom guard rail, has failed.

    Enough.

    Last edited by H.G. Watson, Sr.; 01-23-2011 at 12:40 PM.

  34. #34
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    Default Re: Guard opening limitations explanation

    Quote Originally Posted by Door Guy View Post
    We all know a 4" sphere is smaller than a 6" sphere. What is critical is the shape of the opening. A triangle that progressively gets narrow at each end is much harder for a person to slip through. That's the point here.
    A LARGE triangle is easier to slip a head through than a NARROW slot. The minimum dimensional size of the opening IS the point here.

    Clearly most code officials agree or it wouldn't be in the code. I don't believe this is money issue either.
    Most code officials I have talked with about this agree that a LARGER OPENING is easier to slip through than a SMALLER opening is. It is not the code officials who put things in, or leave them out, of the codes - the codes ARE "consensus" documents, and that consensus includes all affected parties, including manufacturers, who have a great influence on the end result of the code.

    I believe H. G. gets it:
    Quote Originally Posted by H.G. Watson, Sr.
    Get out of the "triangle" thinking box. Even as pictured the area opening is NOT simply a triangle, nor is the opening area simply 2-dimensional! Skip the "largest circle" (and the term is incircle) "that can fit in a right triangle" crud.

    The sphere is allowed to roll, rotate and change orientation. If (a sphere, a six inch sphere, not a circle) it does and can pass through ANY (Three-dimensional!) opening between the stair (not necessarily the tread) and the lower or bottom guard rail the stairway guard test for area below the bottom guard rail, has failed.

    Enough.
    I disagree with someone saying "Enough.", though, as it is not "enough" just because someone says so, it is only "enough" when the discussion/debate is through.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  35. #35
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    Default Re: Guard opening limitations explanation

    As much as EC Jerry and I have agreed on code interpretations in the past I have got to go with Door Man on this one. The basis of our position is not about the "head," but rather the rest of the body following the head through an opening. It's also true that the area of contention is not a triangle, but triangular shaped.

    BTW, are "captured treads" considered POW's in the stair wars?

    Jerry McCarthy
    Building Code/ Construction Consultant

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    Default Re: Guard opening limitations explanation

    Quote Originally Posted by Jerry McCarthy View Post
    As much as EC Jerry and I have agreed on code interpretations in the past I have got to go with Door Man on this one. The basis of our position is not about the "head," but rather the rest of the body following the head through an opening.
    And we do agree on most ... this is one of a few on which we disagree, and the why behind why we disagree.

    "The basis of our position is not about the "head," but rather the rest of the body following the head through an opening."

    Which could well save the child's life.

    It is the head going through the opening and getting stuck, leaving the child to be trapped and strangled by the sides of the opening.

    I know, I know, with a 6" sphere opening within the triangle, the entire body could just fall right on through and down to the lower level - BUT .... that may not result in as serious injuries as if the head only became stuck in the 4" opening.

    It is all conjecture and suppositions, and the 6" is in the code, and undoubtedly there was, at one time, some reasoning behind it.

    From the Commentary: (bold and underlining are mine)
    Guards must be constructed so that they not only prevent people from falling over them but also prevent smaller occupants such as children from falling through them. To prevent people from slipping through a guard, any required guard would need to have supports, spindles, intermediate rails, or some type of ornamental pattern so that a 4-inch (102 mm) sphere cannot pass through it. This spacing was chosen after many years of discussion and because information was submitted to show that based on the size of a child's head, very few children would be able to crawl or walk through a 4-inch opening. The code does provide two exceptions for this spacing requirement, permitting the use of a 6-inch (152 mm) sphere for the triangular area formed by the riser, tread and bottom rail of a guard along the open side of a stair and 4 3/8 inch (111 mm) sphere for the guard on open side of stair treads. See Commentary Figure R312.2 for an illustration of the guard requirements.
    The Commentary does not explain the 'why' behind the two exceptions, even after establishing that "information was submitted to show that based on the size of a child's head, very few children would be able to crawl or walk through a 4-inch opening".

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

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    Default Re: Guard opening limitations explanation

    Quote Originally Posted by Jerry McCarthy View Post
    As much as EC Jerry and I have agreed on code interpretations in the past I have got to go with Door Man on this one. The basis of our position is not about the "head," but rather the rest of the body following the head through an opening. It's also true that the area of contention is not a triangle, but triangular shaped.

    BTW, are "captured treads" considered POW's in the stair wars?
    Thanks Jerry, I like the "captured treads" quote... I just don't see the over concern on the exceptions. I posted a link to pictures of the Mackinaw Bridge that has a Labor Day walk every year. In fact there is a new bridge in our town that has a walk way over the river with horizontal 12" oc rails that is upstream about 100' from a damn. Were sitting here bickering over 4" or 6" spheres. I'd rather have small children use my strairs (which btw was built with 6" oc spacing) than have small children use that sidewalk...

    Randy Gordon, construction
    Michigan Building Inspector/Plan Reviewer

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    Default Re: Guard opening limitations explanation

    Quote Originally Posted by Jerry Peck View Post
    And we do agree on most ... this is one of a few on which we disagree, and the why behind why we disagree.

    "The basis of our position is not about the "head," but rather the rest of the body following the head through an opening."

    Which could well save the child's life.

    It is the head going through the opening and getting stuck, leaving the child to be trapped and strangled by the sides of the opening.

    I know, I know, with a 6" sphere opening within the triangle, the entire body could just fall right on through and down to the lower level - BUT .... that may not result in as serious injuries as if the head only became stuck in the 4" opening.

    It is all conjecture and suppositions, and the 6" is in the code, and undoubtedly there was, at one time, some reasoning behind it.

    From the Commentary: (bold and underlining are mine)


    The Commentary does not explain the 'why' behind the two exceptions, even after establishing that "information was submitted to show that based on the size of a child's head, very few children would be able to crawl or walk through a 4-inch opening".
    I remember some of the "why", and as I recall the retention of 6" sphere bottom rail ex. isn't as quite as how you represented it. The 4" spheres yes, and as I recall it, regarding the reduction to 4" sphere from six overall for guards, and residential only, the editorial remaks are in essence a fair summary.

    Last edited by H.G. Watson, Sr.; 01-23-2011 at 08:27 PM.

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    Default Re: Guard opening limitations explanation

    I'd like to suggest that those of you who have problems picturing the Code requirements for stairs or who would just like to have pictorial information to show your clients (by way of explanation) go to Stairway Manufacturers' Association - Home and open their "Visual Interpretation of the IRC". This is the Stairway Manufacturer's Association and they do a better job than anyone I have seen in explaining visually what the Code means. I think most of you would enjoy looking through this 16 page document. They have versions available for free download for 2000, 2003 and 2006 IRC.


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