How to build stairs on a low or gentle slope or stairs with a small total rise height.

Here we explain how to make stair design calculations for low angle stairs - stairs that are the opposite of "steep".

We explain the design of the stair angle and the calculation of the necessary number of steps, step riser height, total stair height or rise, total stair length or run.

This article series provides stair building calculations for most indoor and outdoor situations and warns about some "in between" stair tread sizes that may be a trip/fall hazard.

Our photo (above left) illustrates construction of a low-slope stairway located in the "Jewish Quarter" in Girona, Spain. These steps are several hundred years old, are worn, and have a bit of a slope to them.

How to Build a Low Slope Stair

Calculate the Step Tread Depth Required to Achieve the Total Horizontal Run

For most indoor and many outdoor steps and stairs we simply choose a standard tread width (say 11") and we allow the number of steps to determine the total horizontal run of the stair case.

Then we "fit" that stair into the building design plan, or outdoors we let the stairs end where they may, provided there is adequate entry/exit room at the stair top and bottom.

But for our example low-slope outdoor stair situation, the stairs described by a reader needed to climb a low slope, traversing an extra long distance.

Here is how we solved that problem.

Check that the total horizontal run of the stairs fits the space

Let's use an 11-inch deep tread to make nice stairs. Actually I don't like an 11-inch deep tread with such a short rise but it's code compliant. [Click any of our images to see an enlarged view.]

• 19 steps x 11 inches per step = 209" - far short of your 336" run.

The total rise needed for the stairs is in conflict with the total run needed for the stairs.

In other words, you can't keep stair riser height within an acceptable range and traverse the horizontal run distance without deepening the stair treads.

This means you're going to make your stair treads deeper, but unfortunately, keeping riser height to within acceptable bounds and making the stair run match the required length, the result may be an awkward halting-walk stairway.

Calculate the Total Number of Steps up or Risers Necessary to Achieve the Total Vertical Rise

If we used the minimum rise/step of 4" then 78 / 4 = 19.5 - we'd have to go to 19 steps (since we can't build a fraction of a step and since we're not going with 20 steps which would have a slightly short rise of 3.9" though the local code official might accept that)

• 78" total rise / 19 steps = 4.1" riser height

Really this means we need 19 steps up or 19 risers to make up the vertical rise - the total change in grade.

How to Find the Percent Slope & Angle of a Low-Rise Stairway

Above is our sketch of a very low-slope stairway proposed by a reader. The stair has to rise 78" over a horizontal distance of 336".

The individual step riser height and step tread depth was given as 15 risers of 5.57" and an individual tread depth or horizontal travel distance of 24".

If we divide the total rise by the total horizontal distance travelled or "run" we have

Percent Slope = (Rise / Run) OR (Vertical Distance / Horizontal Distance) multiplied by 100

78" / 336" = 0.23 x 100 = 23%

A Slope angle expressed in degrees is computed as

ArcTan (Rise/Run) = Slope in Degrees

[ArcTan (.23)] = 12.9 or about a 13° slope for this stair - pretty modest.

This stair can work because of the very wide 24" tread depth, though it might result in what we don't particularly like, a "halting walk stair" that we discuss

at HALTING WALK STAIR DESIGNS for LOW SLOPES or SHORT STEP RISE.

Watch out: we still have to check the riser height and actual number of steps against the horizontal run space as follows.

As you see below, there is a trip hazard (a toe catcher) on these outdoor steps because the landscape ties extend up above the black asphalt walking surface near the end of the stair step. But there is a second trip hazard: the total step depth from nose to riser may be too short for comfortable walking.

Watch out: in reducing the step riser height if you produce a tread depth distance that makes walking awkward or "halting" the result may be an increase risk of stair falls.

Also see STAIR DESIGN for SENIORS

How do we set the step riser height & tread depth for a very low angle staircase?

Reader Question: How do I design an outdoor stair for a low slope long run situation

Perhaps one of the experts here could give advise on this. What are the rules for a low angle staircase? I am planning an exterior (built on grade) staircase on a slope too steep for a ramp.

My rise is 78 in. over 28 ft. and there is additional room for a landing at top and bottom. I am considering 3 ½” risers and 16” treads (using commonly available cement block).

What rules-of-thumb should I follow to build a comfortable walk-able low angle staircase?

If there is some formula to the ideal cadence; I would form this in concrete in order to achieve it.

I do not want to feel like I am taking “baby steps” or alternately taking a “step-and-a-half” all the way up and down. - Tom 6/23/12

Reply: simple approach to calculating the stair rise & run for a low slope stairway - Stair-Building Rule of thumb

Great question. Bernie Campbalik who taught us carpentry, including stair building, used a rule of thumb that basically makes the run longer when the rise is shorter.

I've seen several rules such as

• the sum of one stair or step tread or "run" and one step height or "riser" should always be about 17" or 18" in total
• or two treads plus one riser should add up to around 28" or 29"

The concept is that a low rise stair usually has, just as you suggest, a tread that provides a "longer" walking surface. Up to a point. If we make the rise too short (under 4 inches of rise) it's not a step at all, it's a trip hazard.

Generally we solve the problem of low slope long run stairways by using all platforms - steps that are 36" in length or more in the direction of run of the stairs, or by using a combination of normally sized stair treads (say 11" deep treads with a 6" or 7" rise) along with intermediate stair platforms.

Our exterior stair photo at left illustrates one stair builder's approach to a low slope stairway. He used a combination of asphalt and landscape ties to build these nice looking steps that incorporate several trip hazards.

The projection of the wooden tie up about 3/4" above the walking surface of each step threatens to catch the toe of a shoe, leading to a trip or fall.

And there is a naturally-occurring risk factor - wet surface of the steps. On these stairs the wet wooden landscape tie will be more slippery than the asphalt walking surface. Walkers will naturally tend to step on the wooden surface because it forms the leading edge of each step.

And relevant to your question is the "depth" or run of each step in the direction of travel. While generally it's good to use a deeper stair tread (treads less than 11-inches in depth are not recommended), there may be some intermediate depths (or step run) such as around two feet that make for awkward walking and may risk stair falls. A better stair design may involve increasing the rise and lengthening one or more steps into a platform of 36" or more of horizontal walking surface.

And of course long stair runs due to a very tall total rise (more than 12 feet) also is likely to require an intermediate stair platform as well.

Watch out: make these stair "steps" long enough to avoid a halting-walk stair fall hazard.

See HALTING WALK STAIR DESIGNS for LOW SLOPES or SHORT STEP RISE

Reader Follow-Up:

Dan, Thanks for your response. I now think any rule can at best only make general recommendations for all the low-slope possibilities. I figured that if I could determine the optimum number of steps to comfortably traverse the distance of the slope of my proposed staircase I would then know the correct number of treads.

So I marked off the landing locations and simply walked up and down the slope while counting the number of steps I took as I did so. I repeated this a few times adjusting my gait somewhat and arrived at an average number.

In this case I took 14 steps to travel the slope which equates to 14 treads - 24” long. Then since the landing counts as one of the treads; I divided the rise by 14 which give me a riser height of 5.57”.

I also counted steps made on level ground over the same distance as the length of the stair and came up with 12 so I think 14 is conservative considering the slope but about right for my needs. I am not in a hurry to build but before I do I would still like to hear a professional opinion or two on this. Another possibility might include a landing midway up thus making all the treads shorter? Your input is appreciated.

Reply: stair design basics: calculating step riser height, step tread depth, total rise, total run, intermediate platform lengths

Tom,

I think a sketch of what you're up to would be helpful - if you want to send one use the CONTACT US link at page top/bottom. Meanwhile I'll provide my own versions, not to scale, of your stair dimension proposal and an alternative that you might want to consider and then adjust to your taste.

Based on the figures you provided we describe for other readers the basics of stair design calculations that consider total rise, total run, and step riser height and step tread depth.

Theoretical stair design before fitting to the actual data - how to calculate the number of uniform stair treads

Watch out: at STAIR RISER SPECIFICATIONS we emphasize that stair tread risers must be uniform in height, varying by no more than 3/8" from one step to another. Greater variations in riser height are serious trip and fall hazards.

Back to Tom's exterior low-slope stair design

A consistent riser height of 5.57" would be entirely in spec if you can achieve that for all of the risers, presuming we make all of the steps identical in tread depth - which is SOP. But the landing, if its walking surface is at ground level, doesn't count as a riser. It's a step or tread (really a platform) but not a riser. Let's compare your 14 steps of 5.57" rise and 24" run to your data.

• Total Rise of proposed stair: 14 risers x 5.57 = 78" - that's ok
• Total Run of proposed stair: 28 ft x 12? /ft = 336". 336" / 24" = 14 steps - that's ok except for a possible tread depth issue that we discuss next.

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

Question: how to build steps for people who have trouble climbing stairs

(June 14, 2015) Anonymous said:
i am ask to build steps for an older couple ,one already has a hip replacement an the other getting one done ,,, my steps height is three feet an the distance is five feet they need lower risers

can someone tell what the dimensions would be

Reply: design the stair with a long run, deep treads, shorter rise, and secure handrailings

Anon:

You can make short rise steps by making the stairway run longer. For example if you have a total rise of five feet and you want a 3-inch step rise you'd divide (5x12=60) 60 inches by 3 inches to get 20 steps that you'd need to build to climb up five feet.

Of course you'll want to make the stair treads deeper front-to back to make such short rise steps safe and comfortable.

And secure hand railings on both sides of the stairs will be important for folks for whom stairs are difficult.

See details at STAIR DESIGN for SENIORS

Question: How can I shorten the drop from step to step on my stairs?

4 July 2015 bonita said:
I am no longer able to walk down stairs with the standard drop. How can I make my drop from step to step shorter?

Reply:

Bonita:

When I'm no longer able to make it safely up and down stairs to my office I will probably install a chair lift - see STAIRWAY CHAIR LIFTS

The problem is this: you can indeed re-build a stairway to reduce the riser height but to do so the depth of each tread has to increase significantly too. That means that the entire run (horizontal length) of the stairway will get much longer than it is now, perhaps double.

In the interior of most homes, doubling the run of a stairway between floors would be horribly expensive - if it would fit at all, or making a long stairway that winds or turns - taking more room in other dimensions.

I suspect that the cost of a stair rebuild indoors would be much higher than the cost of adding a stair lift.

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Continue reading at Xspan class="LI_Spaced">STAIR CONSTRUCTION, SPECIFIC TOTAL RISE & RUN - using lanscape tie stairs as example, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• SLIP TRIP & FALL HAZARD LIST, STAIRS, FLOORS, WALKS
• STAIR BUILDING RULES of THUMB
• STAIR CONSTRUCTION IDEAL DIMENSIONS
• STAIR CONSTRUCTION, LOW ANGLE SLOPE
• STAIR CONSTRUCTION, SPECIFIC ANGLE or SLOPE
• STAIR CONSTRUCTION, SPECIFIC TOTAL RISE & RUN - using lanscape tie stairs as example
• STAIR DESIGNS for UNEVEN / SLOPED SURFACES
• STAIR DIMENSIONS, WIDTH, HEIGHT
• STAIR TREAD - HALTING WALK STUTTER STEP

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STAIR CONSTRUCTION, LOW ANGLE SLOPE at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to STAIRS RAILINGS LANDINGS RAMPS

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