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Tread depth/ landing at stairs


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Good question and one I would like to know the answer. I'm smack in the middle of the learning curve I have been into all the books and stuff. The only figures I see for tread are minimums. I have not seen any listings for max tread.

Well, it is not in any code books I can find, and all I see are minimums as well. It just seems to me there should be a max. tread depth to allow for an average persons stride.

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I don't think there is a max tread depth, just a minimum one. But a tread depth exceeding the minimum I would think would still have to meet the minimum variation rule.

I guess another question would be at what depth does the minimum variation rule not apply? If each step is the size of a minimum landing is it step or a landing?

Chris, Oregon

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For decades the rules of thumg have been Riser + Tread = 17-1/2 in. or Riser x Thread = 75; so, if your riser height is 7-3/4in., you're allowed a maximum thread width (depth) of 9-3/4 inches. Using the same numbers and checking it with the second rule of thumb; 7-3/4 X 9-3/4 = 75.5625 and is outside of the rule. So, look at it with a 7 in. riser and a 10.5 in thread and you're there at 17-1/2-inches. Check that with the other rule of thumb and you've got 7 in. X 10-1/2 in. = 73.5 so you're in the ballpark.

It's really a question of the height and length of the area that you must place the stairs within. You establish the maximum distance that the stairs can terminate from the top of the stairwell and still provide you adequate headroom. Then you calculate the height and depth of the treads and risers using a standard mathematical formula, using the floor-to-floor height and the number of treads you're hoping to get, staying under the maximum allowable height and over the minimum allowable thread width, allowing for nosings, and you'll come up with the height and width of the thread. It's a little more involved than that and takes a little tweaking, but that's how it's done. If you know the formula and your calculations are made correctly, you can end up cutting your stringers with oddball sizes, down to the 1/8 in. and end up precisely on the money with every tread exactly the same in height and depth.

So, the width (depth) of the tread is really restricted by the length of the stairs, determined by where you want them to end, allowable headroom, and the height of the stairs from floor to floor.

I guess I've made that clear as mud.

ONE TEAM - ONE FIGHT!!!

Mike

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Might find something in Architectural Graphics Standards.WJ

Thanks, never thought to look there.

It's really a question of the height and length of the area that you must place the stairs within.

The reason I am asking is that I have seen several decks where an upper deck is accessed via a lower deck with half landing steps (think of a sloped property where both decks are fairly close to the ground, but the hill slopes to the lower deck). Say the landings are all 18-30" of uniform depth, and run for about 10 to 12 steps. It screws me up every time I try to walk these things. (kind of like when trying to golf in Japan apparently).

I usually just make a note of the fact that it is an unusual configuration and a potential trip hazard.

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Originally posted by Brandon Whitmore

Might find something in Architectural Graphics Standards.WJ

Thanks, never thought to look there.

It's really a question of the height and length of the area that you must place the stairs within.

The reason I am asking is that I have seen several decks where an upper deck is accessed via a lower deck with half landing steps (think of a sloped property where both decks are fairly close to the ground, but the hill slopes to the lower deck). Say the landings are all 18-30" of uniform depth, and run for about 10 to 12 steps. It screws me up every time I try to walk these things. (kind of like when trying to golf in Japan apparently).

I usually just make a note of the fact that it is an unusual configuration and a potential trip hazard.

As an old-house guy, I've noticed that lots of old stairs -- interior and exterior -- have long treads and low risers. They're much more foot-friendly than modern stairs. I could be wrong, but I think that these designs took into account women with long dresses, who wanted to appear to "float" on the stairs.

Anyhow... tread length would have to conform with how far a person actually steps. The longer the better, as long as the treads create a natural footfall, and don't turn the treads into an awkard two-step (or worse, step-and-a-half) platform.

I've read -- and forgotten -- formulas that were developed for outdoor walkways that require a person to take more than one step before hitting another riser. Those formulas probably came from Architectural Graphics Standards; but heck, they could've come from Rodale Press.

If anybody runs across some of this long-tread info, please post it. I, for one, would find it fascinating.

WJ

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