# Full height wire mesh as guardrail



## Examiner (Jul 14, 2016)

Sorry this will be a little long.
I am looking at a design where the guardrail system is being substituted for a wire mesh design element that goes between the inside stair stingers on a U-stair with an intermediate landing. 

*This is important*; the wire mesh is to be continuous from the first floor anchorage, up between the stair’s stingers to a connection point at the stair’s roof structure.  However, there may have to be a horizontal rated shaft wall cap over the stair before the roof structure is reached.  The distance between the stair stinger runs will leave space for the wire mess to pass but between each stinger outside face distance and wire mess face is a 3 ½” gap.   

The design is also calling for the wire mesh to be attached at the stair stringers, which slope.  This will cause the wire mesh to be more flexible as the distanced between the stringer connections get taller.  Therefore, I see some deflection movement in the wire mesh as it’s connection points get farther apart especially at the top last stair run to the 2nd floor’s landing from the intermediate landing.  It appears that the guard railing at the landings will be the typical rail system but not between the stair stringers.  I am also concerned that the 4” sphere rule must be maintained at ends of the wire mesh (since it is a panel system of a limited width) and the mesh’s abutment close to the landing’s guardrail.

Another concern is how is the contractor going to make the attachment of the wire mesh to the stair stringer as the stingers converge at the intermediate landing?  There is only 3 ½” of gap on each side of the mesh to the stinger face.  Not much working room for tools.   

In the 2012 IBC Section 1607.8 there are sub-sections with the requirements for handrails and guardrails.

I question how this wire mess will comply with the sub-sections loads.  There are linear loads and concentrated loads that have to be complied with. 

Since the wire mess does not have a typical top rail at 42”, is all the wire mess then nothing but Intermediate Rails? 

Will the entire wire mess have to comply with loads as if it was the top rail?

Is any deflection allowed when applying these loads? 

Or is the loads looking only for failure at the applied location? 

Each load referenced in the sub-sections calls for compliance to Section 4.5.1 in the ASCE 7 document.  Of, course I do not have such a document to review.  I guess the document addresses the deflection allowed.  One thought came to mind if a deflection is allowed.  The ends of the wire mesh may deflect enough that will cause the gap between its end and the landing guardrail to be greater thus allowing the passage of a 4” sphere.

Now for the horizontal rated shaftwall question.  It is very possible that the weight of this wire mesh system cannot be supported by attachment to the rated shaftwall cap.  I question whether or not structural connections can go through the rated cap to the roof structure? 

The rated cap is not the finished ceiling.  The design calls for a 2’x2’ acoustical tile panel in a suspended lay-in grid which would require the hanger wires to be attached to the rated cap somehow.  I suspect that exposed furring strips @ 48” OC and perpendicular to the cap’s joist would be attached to the finished side of the cap at the point of the joist so the suspended ceilings hanger wires would have a place to be attached to without penetrating the rated cap.

A handrail will have to be attached with vertical post from the stair stinger’s flange since wall brackets on this side of the stair will not occur.  Of course the handrail’s continuous clearance and allowed vertical interruptions must be in compliance with IBC 1012.4.  In Exception 2 there is reference to baluster attachment for the handrail.  The vertical post to support the handrail are not really newel posts or other obstructions are they?  There is an ADA reference about interruptions along a handrail cannot exceed 20% of the handrail’s length as I recall [ref: 2012 ADA 505.6].  That addresses the handrails connections to something.  

Any thoughts on this design?


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## steveray (Jul 14, 2016)

Can the handrail meet the guard requirements and then the mesh is infill?


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## ADAguy (Jul 14, 2016)

Now that is a real conumdrum.
As to loads, it might be possible to use tension ties with turnbuckles to maintain tension.
However I would not see the wire mesh (opening sizes?) as being a smooth surface adjacent to a handrail (have a photo?)
Do you have FM by-in to this?


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## JPohling (Jul 14, 2016)

If this is expanded metal mesh then that would certainly not be a smooth surface adjacent to the handrail.  More like a cheese grater.


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## steveray (Jul 14, 2016)

Where is the "smooth surface next to a handrail" required?


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## ADAguy (Jul 14, 2016)

Where handrails are required. I find this condition offered by bleacher manufacturers all the time.
It can be a real finger snapper or long nail remover.


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## steveray (Jul 14, 2016)

I meant a code section...I know it is a bad idea. But obviously the person proposing it needs more than "That is a bad idea"...

As far as the penetrations of the exit enclosure, (lid/ cables and such) I would argue that they are not allowed as they serve no purpose related to exiting...


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## ICE (Jul 14, 2016)

steveray said:


> Where is the "smooth surface next to a handrail" required?


1012.7 Clearance. Clear space between a handrail and a wall
or other surface shall be a minimum of 11/2 inches (38 mm). A
handrail and a wall or other surface adjacent to the handrail
shall be free of any sharp or abrasive elements.


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## ADAguy (Jul 15, 2016)

Thanks Ice, I know these things from experience and am not always concerned about the cite as some on the forum are who don't deal with this on a daily basis.


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## steveray (Jul 15, 2016)

Hunh....No more block stairs I guess....


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## Examiner (Jul 15, 2016)

Gentlemen,

Thanks for the responses.  I currently do not know the composition components of the screen between the stair stingers.  It appears to be a screen material that allows seeing through it to allow viewing between stair runs and I guess the designer is trying to use it as a wall between the stair stingers.  Not sure if it is some sort of sun screen with louvers as blinds, a diamond wire mesh or hog wire.  The designer has not shared the info with me.  He is in Design Development at this point.  I am the office Code Reviewer as well as a Senior Architect. I review plans during the DD’s and CD’s to try and catch Code issues, ADA issues and detailing issues that all could result in a Change Order that someone will have to pay for resulting from errors.  It is good to know the Section 1012.7 that addresses the other surface textured finish beyond the handrail.  I missed that one.  That puts another code compliance to this item I am questioning.  I would assume that masonry even though could be an abrasive surface is really not much different than a concrete wall.  Same can be assumed for textured finishes on sheetrock.  You can fall against them and scuff yourself so unless the Code defines what sharp and abrasive elements are, I would assume the aforementioned wall surfaces/finishes are really not abrasive enough. 

However, if the design of this screen system cannot comply with Section 4.5.1 in the ASCE 7 then the design is useless.  I was actually asked why I was critiquing and questioning the design by the young whippersnapper.  That is why I was asking if anyone had a copy of the ASCE mentioned.  The load requirements for the guardrail’s components may disallow the design.  I guess I will just tell the designer that he needs to get a letter from whomever the vendor is for this screen system to state that the system complies with the design loading for all the guard railing components and address the compliance of the finished surfaces to Section 1012.7. 

As for the rated horizontal shaft wall cap at the top of the stair.  I am not sure you can penetrate it with structural items.  HVAC maybe with a fire damper.  If no one can answer that one, I guess I will ask a sheetrock vendor who has shaft walls.

Thanks for the help and advice.


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## steveray (Jul 15, 2016)

No penetrations that do not serve egress (with limited exceptions of course) 1019 in 2003, not sure where it is in the newer codes...


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## tmurray (Jul 15, 2016)

steveray said:


> Hunh....No more block stairs I guess....



Just needs parged behind the handrail.


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## tmurray (Jul 15, 2016)

Examiner said:


> I guess I will just tell the designer that he needs to get a letter from whomever the vendor is for this screen system to state that the system complies with the design loading for all the guard railing components and address the compliance of the finished surfaces to Section 1012.7.



That's what we usually do, unless the approval is just common sense. It's fun to watch people who think they are smarter than they actually are, scramble when you start blowing holes in the documentation they've provided.


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## Phil (Jul 16, 2016)

ASCE 7-10 is very similar to IBC section 1607.8


4.5.1 Loads on Handrail and Guardrail Systems
All handrail and guardrail systems shall be designed to resist a single concentrated load of 200 lb (0.89 kN) applied in any direction at any point on the handrail or top rail to produce the maximum load effect on the element being considered and to transfer this load through the supports to the structure.

Further, all handrail and guardrail systems shall be designed to resist a load of 50 lb/ft (pound-force per linear foot) (0.73 kN/m) applied in any direction along the handrail or top rail. This load need not be assumed to act concurrently with the load speciﬁed in the preceding paragraph, and this load need not be considered for the following occupancies:

1. One- and two-family dwellings.
2. Factory, industrial, and storage occupancies, in areas that are not accessible to the public and that serve an occupant load not greater than 50.

Intermediate rails (all those except the handrail or top rail), and panel ﬁllers shall be designed to withstand a horizontally applied normal load of 50 lb (0.22 kN) on an area not to exceed 12 in. by 12 in. (305 mm by 305 mm) including openings and space between rails and located so as to produce the maximum load effects. Reactions due to this loading are not required to be superimposed with the loads speciﬁed in either preceding paragraph.


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## glzath (Jul 18, 2016)

tmurray said:


> Just needs parged behind the handrail.



Or block filler and two coats of paint.


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