deck stair run: how to pick it

[adrian]

I need to build a small deck stair. My total rise is 24.5 inches. I am planning a rise of 6.125 inches per step. But what should the run be? I consulted three deck building books and got answers ranging from

11 inches to 16 inches! Quite a spread. People don't seem to adhere to the same rules (e.g. the 17 rule) as for interior stairs. I was thinking I could use four 4 inch deck boards which would give me a tread of about 14 inches which is in the middle of the range recommended in the books. Is that reasonable?

[Edwin Pawlowski]

If you pulled a permit and will have it inspected, it does not matter what I think is reasonable. It matters to the building inspector. There are codes that apply to stairs. According to this web site, 14" is max.

It does the calculations for you.

[Harry K]

Yes the rule of 17 (or even 19) gives a very nice run/rise ratio if you stick with a rise of 6-7". Much over that gets into an awkward pace when using them. The 16" you mentioned would be way out of reasonable limits.

Harry K

[adrian]

That web site refers to interior stairs, not deck stairs. As I noted in my original post, it does not appear that deck stairs are designed the same way as interior stairs. The books typically say that space is not at a premium like it is for interior construction, so the stairs can be built with a longer run than inside (with a general implication that larger runs are better.) My interior stairs basement have a 9 inch run which I believe is the minimum allowed by my local code. Nobody suggests such a design for exterior stairs.

Here's a deck building reference that says just what I noticed above in different sources: 11" - 16":

[Edwin Pawlowski]

I see you post from an cornell.edu account. Lots of education, but no idea how to use it.

The site I sent you to gave information on rise and run and recommendations along with minimum and maximum. It does not matter is the stairs are inside, outside, first floor, or to the penthouse. There are minimums and maximums and less comfortable and more comfortable. As I stated, there are codes and there are reasons for those codes.

The only difference between interior and exterior is the location and sometimes the way stringers are cut for style.

[adrian]

>

Great. So I can add your site's recommendation (12" run for 6" rise) to the three sets of recommendations I already have from the deck books I've read and have perhaps four run lengths to pick from now. But how does this help determine what will be the best run? Why should I believe your site's recommendation which is just an option in a calculator's menu over my other references? Certainly that site gives the least justification of any reference I have yet consulted on this topic.

It doesn't give any information whatsoever on what the reasons are behind the codes, just a vague and I think possibly misleading statement about the code. (Like where does code allow a 8.25" run???)

In fact, I think it is typical for code to impose a minimum run but no maximum run. So indeed I know from code that I should not make my run 8 inches. But there's nothing enshrined in code that says I shouldn't make it 16, or even 25.

I read

that studies found that reducing the run below 11" significantly increases accident rates on stairs. But builders have successfully resisted codes that require an

11" run (instead of 9") because of the loss of floor space this would cause. The same source claims that it has been standard in the USA to build interior stairs with a 9" run and exterior stairs with an 11" run (but the same 7" rise in both cases). No difference? My point is that the location is very important. Inside space is (potentially) scarce and you may need to make stairs steeper than the ideal to conserve space. This means that rules of thumb and guidelines designed for indoors wouldn't necessarily be optimal for outdoors. It depends on the underlying reasons for the rules, which are rarely evident.

[Edwin Pawlowski]

Didn't read the whole thing did you? The 12" recommendation was for elderly people. something to consider since we all hope to be elderly some day. What is "best" for you may not be "best "for me. The only real way to determine what suits you is to build a mockup or measure some existing steps. No book can tell you that. You have to walk some steps.

At that great institution of learning you are at, they must have many different styles of steps inside of buildings, outside the library, front entrance to the dorms. Walk them. see what works for you. too long of a run , too shall a rise makes for tiring walking, too short makes for stability problems.

I don't know if you are 4' 5" or 6' 9" so how can any book say way what is best for you?

I'd use a 1 x 12

[Goedjn]

The stair-treads should be deeper than a boot-shod foot is long. That means 11" or more. Since the easiest thing to make them out of is 2x12s, use whatever tread-depth that is. (11 1/4")

Nosings are a trip-hazard. Don't use them outside. The stair-rise should be somewhere between 6" and 8", whatever divides evenly into the height of the deck. If that's variable, then go with a height that allows you to use a 1x8 plank unmodified as the riser.

[adrian]

Indeed, walking steps would be ideal. Unfortunately, the steps that are convenient to try aren't diverse. I'll admit that I hadn't given serious consideration to building a mockup (thinking it to be too time consuming to try a variety of runs) but after thinking about it some more I think it's not as much trouble as I thought. I can probably pile up bricks and cinder blocks and wood to different heights to support treads.

You have made an incorrect assumption about my location.

If optimal stair design depends on height a book can explain the relationship. If it depends on other variables this too can be explained in a book.

I read that it was better to avoid the wide stock and use narrower boards because of the risk of the wide boards cupping. What do you think of that? I notice that you and someone else both suggest using

12 inch wide material, which would certainly be easier. (I'm using ipe.)

Do you agree with the other poster that there should be no nosing?

[Edwin Pawlowski]

My deck steps are 1 x 12 and are still flat after about 18 years. The potential for cupping is there though, and I've seen steps made with two 1 x

6 instead of a single 2 x 12. The slight gap between them helps rain to run off also. One typical difference with indoor versus outdoor is the absence of a solid riser. Outdoors there is snow and rain to contend with so you want to be able to clear it easily.

I'd probably not use a nosing, but if the tread is sufficiently wide, I don't think it is a problem.

If you are putting a finish on the steps, consider a sprinkle of play sand on them to avoid becoming slippery. We did that on an outdoor ramp at work and although the sand is barely visible it makes it much safer for walking.