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Glass Baulisters/ No Top Rail

mtlogcabin

mtlogcabin

SAWHORSE
Joined
Oct 17, 2009
Messages
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Location
Big Sky Country
This is outside my jurisdiction where ther is no code enforcement. A lake view house that is removing the log baulisters and replacing with glass panels. The owner does not want a top rail because it will interfere with the view. I believe it can be done per the exception in 2407.1.2.

Question is there anything else the contractor should be aware of? He wants to do it right but the client has his own ideas and does not see the additional expense. The highest deck is about 40 ft above the ground and the temps can be 20 below to 105 above with a south eastern exposure.

Section 2407.1.2 Support.

Each handrail or guard section shall be supported by a minimum of three glass balusters or shall be otherwise supported to remain in place should one baluster panel fail. Glass balusters shall not be installed without an attached handrail or guard .

Exception: A top rail shall not be required where the glass balusters are laminated glass with two or more glass plies of equal thickness and the same glass type when approved by the building official . The panels shall be designed to withstand the loads specified in Section 1607.7.
 
I agree that the exception is pretty clear. Unfortunately, it only references 1607.7, and does not specify a safety factor of 4 as is referenced a couple of paragraphs up in 2407.1.1. However, I think that the safety factor of 4 clearly applies.
 
That exception is new to the 2009 IBC. Previous editions required the top rail because glass fails instantly while metal will usually flex before failing. This has long been an issue in stadiums and arena where glass rails are preferred because of sight lines and the top rail impacts sightlines. I will have to go back and read the code change documentation on this one.

2407.1.2 Support. Each handrail or guard section shall be supported by a minimum of three glass balusters or shall

be otherwise supported to remain in place should one baluster panel fail. Glass balusters shall not be installed without

an attached handrail or guard.

Exception: A top rail shall not be required where the glass balusters are laminated glass with two or more glass

plies of equal thickness and the same glass type. The panels shall be designed to withstand the loads specified in

Section 1607.7.

Reason: At the time the provisions of Section 2407.1.2 were developed the dominant glass used for baluster panels was single tempered glass.

This glass was structurally adequate and had been successfully used. The required top rail was to provide a degree of protection should one

baluster fail for any reason. Tempered glass characteristically may fail in a manner where it evacuates the opening.

In some applications the use of a top rail is an undesirable visual barrier. A typical example is the guard at the front of the spectator levels of

sport arenas and theaters. In a number of these installations the top rail has been eliminated. The balusters have been laminated heatstrengthened

or tempered glass complying with the IBC structural requirements for top rails. Variances from Section 2407.1.2 have been historically

granted by building officials.

If one ply of the laminated glass breaks, the glass will remain in place. Unlike single tempered glass, it will not evacuate the opening. Even in

the rare instance where both plies may simultaneously fail, the glass will remain in place.

It should be noted that the GICC has submitted another code change which proposes to delete Section 2407.1.2 in favor of reference two ASTM

standards. If the section is deleted as recommended in the other proposal, the proposed exception is not required and this proposal should be

recommended for Disapproval.
 
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Mtlogcabin,

This has log been an issue that few truly understand.

1.) if this is a private home under the IRC and not the IBC then the glass is subject to the 4 times safety factor applied to the 200 lb point load at the top of the guard.

Thus the glass has to withstand an 800 lb point load on the edge of glass, though engineers will argue need not IRC simply states point load 200 glass 4 times safety factor.

So simply, show proof that the tempered glass edge will take the 800 lb point load and your golden.

2.) If this is a R2 condo or IBC home because over 3 stories or other, then as COUG DAD pointed out the wording in 2407 in 2009 does allow with the exception. However some argue that single family homes built under the IBC are note required to follow chapter 24 because of the exception in 1607.7.1

1607.7.1 Handrails and guards. Handrails and guards shall be designed to resist a load of 50 pounds per linear foot (plf) (0.73 kN/m) applied in any direction at the top and to transfer this load through the supports to the structure. Glass handrail assemblies and guards shall also comply with Section 2407.

Exceptions:

1. For one- and two-family dwellings, only the single concentrated load required by Section 1607.7.1.1 shall be applied.

1607.7.1.1 Concentrated load. Handrails and guards shall be able to resist a single concentrated load of 200 pounds (0.89 kN), applied in any direction at any point along the top, and to transfer this load through the supports to the structure. This load need not be assumed to act concurrently with the loads specified in Section 1607.7.1.
Click to expand...
Thus, built under the IBC 1&2 family homes do not have to apply the 4 times safety factor (debated time and time) because the link to 2407 in under 1607.7.1 which is now exempt.

In any case, the one thing I will point out is that the no edge post design guard system shown in the pictures are marketed for pool enclosures which have no load requirements and are now being used as guards.

Lastly, if you are the inspector and you receive this type of installation I would recommend that the applicant look in to Sentry Glass by Dupont or a competitors product of the same make up.

This laminated glass stays right in place when both sides of the glass is broken, there is a video out there showing the a glass panel standing straight up with nothing holding it in place except the shoe at the bottom, they break both panels and try and push over and it all stays right in place.

Pricy, but great stuff for glass guards
 
Thanks for the input I will pass the info onto the contractor. The house is located in an area with NO building code enforcement I did not find in the 2006 IRC if a top rail was required or not so I went to the next code the state adopted the 2009 IBC. This is an extensive remodel on an existing home. I was there for an insurance inspection a couple of months back and I may get called again when it is finished. Even though we are not suppose to look for code violations they do ask for recommendations to reduce risk so to answer peach if I get called back he will either be paying a big premium or get cancelled. The bothersome part is everbody on this board would know who this owner is and money is not a problem.
 
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