Handrail to Stud Wall 2

[bookowski]

I'm assuming that this has been worked out since it's done all over the place but what is a typical detail for attaching a railing to a stud wall (wood or metal stud). I have not encountered this before as it's usually delegated to others but an architect asked me to look at his detail. From what I see it looks common to specify blocking aligning with the anchor locations. I don't see how the 200# works for this detail, in particular if you apply 200# vertically on the rail, which is about say 3"+ away from the connection. What keeps the blocking from rotating?

The only way that I see this working is to have them lay out and align studs with the anchor locations and then use a tall plate to take the T/C forces from the 200#. Is there a better detail?

 

[precast78]

Most handrails have connector that can slide. So yes, you will line it up with the a stud. The manufacturer of the handrail probably already assume certain height of wall and design it with that 200 lb force.

If you design the handrail your self then yeah, I would think you want to line it up with a stud. There is a lot of coordination with the framer though unless you make the connector able to slide.

 

[SteelPE]

This is one of those details that I have never really looked at. I guessing others have never really looked at it as well. As you stated, the standard detail is to add blocking between the studs to attach the bracket. I don't think I have seen anyone that aligns the brackets with the studs.... but maybe that is just my clients.

 

[bookowski]

I can see the blocking taking 200# in/out, but vertically where you impose a moment seems like it would never work - at least on paper.

 

[Ron]

bookowski....are you talking about a "free hanging" handrail attached directly to a wall, the handrail along a stair stringer guardrail or a guardrail for a balcony or such? They are all attached differently. The one that actually has the lower load is the "free hanging" handrail along a wall. It is debatable as to whether the 200# in any direction applies to this one. It could be interpreted either way as it serves more as a guide rail than a handrail. In my opinion it should be able to withstand 200# in direct tension. It is difficult with the architectural attachments to get these rails to handle the moment applied when load is straight down.

To answer your original question, the blocking is usually set to attach between studs as it is rare to get exact alignment for the brackets over a stud. It is also rare that the blocking is able to withstand design loads, but that doesn't stop the field crew from installing anyway!

 

[bookowski]

Ron - My particular case is a 'free hanging' handrail attached directly to a wall. It is a stair in a retail space and as you go down the stair the sides are full height stud walls clad in a wood panel system. The rail needs to go through the wood panel and have a concealed connection to the backup metal stud wall.

If the 200# didn't apply vertically then it would be easy, but I've never seen that interpretation - but I haven't looked at many of these. Is this considered a 'guide rail' as you said and is therefore not subject to the same loading requirements?

 

[boo1]

Residental we just add solid blocking between the studs

 

[DBronson]

bookowski:

If you're in the US and subject to the IBC (International Building Code) the 200# (applied in any direction) is a code requirement. There's also a requirement for 50# per linear foot, applied in any direction. These loads do not act together. Section 1607 of the IBC has the details.

Regards,

DB

NB: These requirements are in ASCE 7 as well.

 

[dik]

Just a caution... some jurisdictions only permit a handrail to be a certain dimension that differs from a guardrail. Catch the following from correspondence to a young engineer I mentor:

The size of the handrail exceeds code maximum by 6 mm. The specified size for the handrail was determined by making it the same size as the guardrail which is at the opposite side of the wall handrail at the same stair case. My calculation indicates the 1.25" diameter STD pipe is not adequate for the guardrail of that height and spacing. The architecture drawings (Addendum) also indicates 1.5" metal pipe for handrail.

It is not a matter of the handrail being under designed; it is more than adequate from a strength and serviceability consideration. The size, moreover, is not too large to prevent an individual from using it for a firm grip.

If necessary, ??? can approach the City of ??? and advise them of the non-conformance and obtain a variance from the code requirement. If this is not forthcoming, it may be necessary to appeal the decision to the ??? Building Commission.

In the event the variance is declined by the ??? Building Commission, it may be necessary to replace the offending handrail.

In the interim, can you determine if the shop drawings were reviewed by either the Engineer of Record, the Architect for the project, or the Contractor? Can you advise me the results of their review.


Dik

 

[Bagman2524]

I think the architect needs to come up with some type of structural members within the wall that can handle the 200 lbs./50 plf. Most stairs I've come across are "exit stairs" which have to be within fire proofed walls and are therefore either solid concrete or filled concrete blocks. I just don't see a metal stud be capable of supporting the design loads.

Faith is taking the first step even when you can't see the whole staircase. -MLK

 

[bookowski]

It looks to me like the studs themselves can be shown to work fairly easily. Just to be clear they don't cantilever, it's a solid (full height) stud wall along the stair sides. The rail to blocking detail is what seems funky to me. I assumed that this is very common and I was just missing something here in the detail/load path but it sounds like maybe this is one of those things that usually gets drawn by an architect and doesn't work (on paper).

 

[Jerehmy]

Can you provide a sketch.

 

[SAIL3]

Sooner or later one has to use engineering judgement and common sense in interpreting the codes...the codes can not cover every possible situation nor should they. I would analize loading situations that are possible and reasonable and go with engineering judgement. With that in mind I would second Ron's approach.
If you can come up with a plausible and reasonable scenario where the rail would experience a 200# vertical load, please share it with us.
There is a site called juliusblum.com that you may want to look at.

 

[Jerehmy]

You can't think of a single situation where a handrail would have a 200# load on it? Let's say a 200#+ man starts to fall and grabs the handrail? It'd probably be even more than 200# equivalent static load since he's moving.

You can't say it's not made for that. If it's there, someone starts falling grabs it and it breaks, someone is getting sued.

 

[wannabeSE]

For metal studs, I typically see a 6" x 16 GA track used for backing. OSHPH (conservative building authority for Calif hospitals) uses the same for grab bar backing in there preapproved details. See page 48 of their metal stud partition details

http://www.oshpd.ca.gov/fdd/Pre-Approval/2013CBC_StdPartitionWallDetails.pdf

I have never tied to justifying the backing for handrails. But, I have been challenged with attaching some handrails to the backing.

 

[Ron]

If you look at the details for a wall handrail in the "Metal Stair Manual" by NAAMM, the supports are more architectural than structurally robust; however, we still have the code requirement for 200 lbf in any direction. Ultimately depends on the configuration of the mounting bracket and how well you can capitalize on the reduction in prying force from the applied moment based on the wall plate attachment configuration.

 

[BUGGAR]

WannabeSE thanks for the OSHPD manual. I rarely use it but when its needed..............


Is it just me or from a distance, does the figure in the OSHPD seal look like a hand with its fingers crossed?

 

[bookowski]

Jerehmy - I agree, doesn't seem hard to envision the 200# scenario to me. If I took a spill on the stairs that bar would get 200#.

Wannabe - Thanks for the link, that is along the same lines as other details I've seen. I have not gone through the analysis in detail but eyeballing it I'm surprised if it works for the situation of 200# applied vertically on the rail and the resultant m = 200# x 'e'.... it doesn't seem like the track would have the torsional stiffness or capacity.

 

[bookowski]

Came across this system - somebody put their stamp on it. Not very different from the OSHPH concept. Maybe it calcs out, didn't look like it would to me.

http://www.perfectwall.net/metal-framing-info/smooth-wall-flush-mount-ada-compliant.html

 

[woodman88]

Contractors do not like to install a Simpson A35 each end of the block as I have detailed. Wonder if they used them?

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.