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J.Saravana Balaji
Joined: 25 Dec 2007
Posts: 17
Location: India
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 Posted: Mon Mar 31, 2008 5:48 am Post subject: Missing Step in a dog legged staircase. |
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In most of the firms ,while designing a doglegged staircase,last step of a fight (near the landing)will be missed delibrately,which they term it a missing step.
As per my understanding the step down from the landing will be missed so that we can have a rectangular soffit with out any offsets.
Is that true or there any other reason for missing step.Because some firm have the practice of missing the step that is going up from the landing.
The sketch enclosed is self explanatory kindly clarify.
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Kevin
Site Admin
Joined: 13 Apr 2004
Posts: 1048
Location: Eugene, Oregon
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| Posted: Wed Apr 02, 2008 8:00 am Post subject: |
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| From a US perspective, it is hard for me to visualize what you are talking about. Is the step skipped horizontally, or vertically? Perhaps if we could see the mentioned graphics, you'd get more response. Thanks!
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lekizz
Joined: 11 Jan 2006
Posts: 954
Location: UK
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| Posted: Wed Apr 02, 2008 8:37 am Post subject: |
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As Kevin says, the sketch is missing so it's difficult to know exactly what you are describing. But I find that, where a staircase requires a handrail, the steps to/from a landing may be staggered to allow a smooth handrail transition between one direction and the other.
My scanner and pdf writer are not connected to this PC so I can't offer you a sketch either.
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J.Saravana Balaji
Joined: 25 Dec 2007
Posts: 17
Location: India
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lekizz
Joined: 11 Jan 2006
Posts: 954
Location: UK
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| Posted: Sat Apr 05, 2008 6:53 am Post subject: |
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| I don't know the reason why your firm prefers the LHS version. In the UK another consideration is that (to meet accessibility regulations) the handrail normally must extend 300mm beyond the edge of the landing. That would be possible with your Plan 2 but not Plan 1. Though for domestic staircases it does not matter. Who designed your staircase? Why don't you ask them?
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J.Saravana Balaji
Joined: 25 Dec 2007
Posts: 17
Location: India
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| Posted: Tue Apr 08, 2008 3:46 am Post subject: |
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In the UK another consideration is that (to meet accessibility regulations) the handrail normally must extend 300mm beyond the edge of the landing.
Unable to follow,Could you please explain with a sketch.
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J.Saravana Balaji
Joined: 25 Dec 2007
Posts: 17
Location: India
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| Posted: Wed Apr 09, 2008 4:07 am Post subject: |
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Find enclosed the sketch with the handrail.In both the cases the handrail is not extending the landing.
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teamjdc
Joined: 25 Oct 2007
Posts: 145
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| Posted: Wed Apr 09, 2008 8:35 am Post subject: |
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I think you're reading way too much into some pretty basic strategies for solving simple problems.
Also, if you're access codes are like ours, continuous rails do not require extensions. So, either your code is different, or some architects do not know how to apply it.
In any event, you're looking for something that isn't there.
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JWmHarmon
Joined: 15 Apr 2004
Posts: 105
Location: Ohio
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| Posted: Wed Apr 09, 2008 12:30 pm Post subject: Handrail extensions |
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The intent of the handrail extensions of 12 inches (30 cm) is to provide for the user to grasp the handrail before taking a step down or up. Grasping the handrail before stepping up or down helps to prevent falls from missing the step. It gives an additional margin of safety. It also gives a tactile clue to the user that there is a transition from steps to landings.
Falls on steps are one of the major sources of injuries in buildings.
This web site shows handrail extensions (scroll to the bottom for figures 505.10.1, 505.10.2, and 505.10.3):
http://www.access-board.gov/ada-aba/html/tech-05.html
All handrails should terminate in a return to the wall, a return to the floor or a newell post.
The purpose of this return is to prevent purse straps or attache case straps from catching on the end of the handrail. A strap getting caught on a handrail end will tend to pull the user off balance resulting in a backwards fall with the potential for head and neck injuries or broken arms.
_________________
When building or manufacturing always ask, "How will we recycle that?" - JWmHarmon |
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mx2
Joined: 18 Jan 2006
Posts: 1814
Location: Miami, Florida
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| Posted: Wed Apr 09, 2008 1:15 pm Post subject: |
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By code, if the handrail is continuous, particularly on a switchback stair as shown, it is not required to extend an additional 12"...note that I said additional. The handrail, for construction and practical reasons, must extend at least one tread length in order to maintain the same grasping height of the handrail...
...however, our friend here, M. Balaji, has presented a good option and good question/alternative. When the two edge of risers align (as in most stair designs) then the handrail has to "drop" one riser at the switchback...the 180 degree turn...in order to maintain the same handrail grasping height. Try drafting the detail, keep the handrail 34" above nose of treads and you'll see...but by offsetting one more tread, the switch will end up relatively close. And therein lies the answer M.Balaji...the idea is to add one more tread at the higher flight of stairs so that it terminates at a lower point for the switchback...if you did the opposite (Plan-1) then you actually worsen the "drop" of handrail...although you're right, you would get a nicer clean soffit below. But most of the time, people are looking at their feet when descending or climbing a flight of stairs, and not the soffits...
mx2.5
_________________
*Art of Architecture: The conscious use of skill and creative imagination in the production of an aesthetic building.
*Science of Architecture: The calculated use of technical skill and knowledge in the construction of a functional building. |
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