Amateur exterior stair & deck construction © D Friedman at Exterior Stairways: Guide to Outdoor Stair, Railing, Landing Construction Codes & Hazard Inspection

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Exterior stairway construction details & suggestions for safe stairways:

This document provides building photographs, and examples of defects found in inspecting indoor or outdoor stairs, railings, landings, treads, and related conditions for safety and proper construction. We include references to articles cataloging the causes of stair slips, trips, and falls and to building code specification details for proper stair, landing, balcony and railing construction.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Exterior Stair Code Specifications & Construction Recommendations

Amateur exterior stair & deck construction © D Friedman at A stair inspection checklist provided in this document outlines information to collect during a field investigation of the condition of an interior or exterior stairway for safety defects.

While in general the building code specifications for exterior stairs, landings, and railings are the same as for indoor star is, we often see special trip hazards at exterior stairs and walks, conditions that do not occur indoors, and details which may escape some building inspectors.

When we encounter steps and a deck such as the version shown in our photo (above left) we are confident that the construction was done without the benefit of building permits and code approvals, is unsafe, and may harbor other hidden structural or safety hazards.

And some stair design requirements, such as stair treads that will not hold water, naturally pertain principally to outdoor stairways. We add some more subtle warnings about outdoor stairs and stair construction, and tips or tricks of carpentry and masonry to avoid problems with stairs.

Construction Requirements for Safe Outdoor Steps, Stairs, Railings, Newell Posts

Stair support unsafe (C) Daniel Friedman

Stair support unsafe (C) Daniel Friedman

Figure 1-31: Cupping of flat sawn lumber (C) Wiley and Sons, S Bliss

Exterior Stairs - Incomplete, Unsafe, Missing Guardrails

Unsafe fire exit stairway (C) Daniel Friedman

The exterior stair shown above appears to have been installed as a fire-exit way, but lacks a guardrail around the stair top balcony. It is exactly during an emergency that a frightened user is more likely to fall at this location.

Safety & design questions for sloped, pitched, & narrow exterior masonry steps

Reader Question:

My mother is elderly and is moving from her home to a co-op building. Her unit is on the first floor and her patio is served by an outdoor staircase made of flagstone steps.

There is a steep incline to the steps, and they seem to be too narrow for the incline. We have asked the board of the co-op if we can widen each step from their current width of 23 1/2 inches to 30 inches.

Sloped narrow exterior stairs (C) InspectAPedia & P.O.

The board is opposing our request to widen the steps on aesthetic grounds, and not considering my mother's safety. They are allowing us to rebuild the staircase, as it was poorly built to begin with.

Sloped narrow exterior stairs (C) InspectAPedia & P.O.

Is there a way to determine what the proper width of each flagstone should be (side to side) based on the incline of the staircase?

What I would like to do if possible is to show the board from a mathematical standpoint what the proper width of the steps (from side to side) should be in relation to the steepness of the incline.

If I can't appeal to them on ethical or moral grounds, maybe I can convince them that it's the proper thing to do based on the incline to create a safe staircase for my mother.

I have attached some photos below for reference, however they really don't show how steep the steps actually are when you try to climb them especially when they're wet or icy or have snow on them.

A wider step from side to side would definitely make one feel more confident negotiating the steps up and down. I appreciate any technical input or knowledge you can provide that would help me with my request to the board. Thank you. P.O. 11/10/2012

Recommended stairway width for an exterior stair


From your photos, two of which we include above, I see a trip hazard where someone routes a garden hose across a stair tread - the hose can easily wind up in the walking path and is a serious trip hazard for anyone, young or elderly.

In a companion article STAIR DIMENSIONS, WIDTH, HEIGHT you can read standard stair measurements. There you'll find that the stairs you describe are more narrow in width than recommended.

You will want to involve the local building code officials in the jurisdiction where your mom's stairs are located. But we point out that in general, the minimum recommended stair width is between 34" and 36" Across the width of the tread.

Private stairways shall be a minimum of thirty-six inches wide. Trim and handrails may not encroach into this
minimum width by more than 3 1/2 inches.

The maximum rise of each step is eight inches; the minimum rise is four inches.

The minimum run is nine inches. The largest tread width or riser height in any flight of stairs
shall not exceed the smallest by more than 3/8 inch.
- stair codes vary; this quote is from he CBC 1003.3.3 Stairways and Landings model code

The stairs you describe are a less than the minimum recommended width, and in my OPINION we should do all feasible to make stairs safe and navigable particularly where their users are known to include people at extra risk of falling injuries.

Recommended pitch for drainage on exterior stairs

In a second companion article STEP TREAD DIMENSIONS you will see that although it makes perfect sense to provide a slight slope to exterior stair treads so that they will drain, the slope must be very slight, not more than 1 inch of rise in 48" of run.

The "incline" of the stairway - a consideration in your original question - does not determine the recommended stairway width. But indeed if the steps are too pitched (say for aggressive drainage) that excessive pitch is itself a trip and fall hazard.

Stair tread slope (out of level on walking surface) - (slope or "rise" must be <= 1 in 48) -- Source: IRC

Other things to check for exterior stair & walkway safety

Reader Question: Do we need to install a handrailing along these exterior stairs?

New masonry stairs needing a handrailing (C) InspectApedia

We just paid alot of money for the retaining wall and steps and the contractor did not include a handrail. When we go for final inspection from the township, is there any way we can say we DON't need a handrail since there are walls on the sides? Thanks! - Anonymous [by private email] 2016/05/04


In my opinion your stairs need a handrail.

A person who is falling won't get meaningful help in trying to arrest the fall by attempting to hold on to the wall. It's not that a properly-installed handrailing absolutely prevents falls, but it reduces them by giving the stairway user a chance to stop a fall by grabbing a secure rail. In sum, I prefer to consider safety first and code compliance second, even if the locsl inspector OKs the stairs.

Please see HANDRAILS & HANDRAILINGS for details.

Also see RAILING CODES & SPECIFICATIONS but keep in mind that your local building inspector is the final legal authority on building code requirements where you live.

Reader follow-up:

Okay. Thanks! We will do a handrail

Full Text of IRC & Other Stair Building Codes 2006, 2012

The ICC has free, limited, live, online access to some of the latest codes, but I couldn't find the free link for IRC immediately.


Continue reading at STAIR DIMENSIONS, WIDTH, HEIGHT or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see BUILDING CODE DOWNLOADS - free downloadable PDF files of building codes & standards

Or see EXTERIOR STAIR CODE FAQs - questions and answers posted originally at this page

Or see






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EXTERIOR STAIR CONSTRUCTION & CODES at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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