Know Your House: Stair Design and Construction for a Safe Climb
A stair is also an essential part of the structure in any home that’s more than one level, even when there are merely a couple feet between degrees.
In a way that a stair is among the most important pieces of structure in a home. More frequently than not, a residence’s stair becomes a backdrop for a number of life’s significant events, such as those high-school-prom and wedding-day photos. And as a daily utilitarian item, a stair is an excellent way to choreograph movement through a home. It is no wonder that designers and architects spend so much time designing stairs, which true craftspeople build stairs that are absolute joys.
In all a stair’s beauty, choreography and craft are elements that unite structure and material — all set to a required geometry to ensure a stair is both a joy to traverse and safe. Some things are no longer allowed, like risers that are too steep, treads that are too narrow, uneven riser heights and tread depths, and much more.
Let’s take a look at a few of the considerations that go into the design and construction of a simple, straight-run stair.
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A straight-run stair is merely that: a stair that doesn’t curve or turn or something different. It just simply travels in a direct line from a lower floor into an upper floor and vice versa.
Although we’ll be looking in detail at a closed-riser stair, this stair has open risers. Some building departments don’t allow such a stair design, since there’s a panic that little children may slip between the treads and fall.
What is interesting in this stair is the open risers are kept narrow, 4 inches or less, to comply with the local building code and be open.
Bud Dietrich, AIA
As mentioned at the outset, a stair is an architectural element that enables individuals to quickly move between differing floor levels in a construction. Let’s help Bob here find his way from the second floor to the first floor without needing to slide down a fire pole, jump or require an elevator.
Bud Dietrich, AIA
Get the angle . The first thing we’ll do is set up the geometry for our new stair. We’ll split the total rise (the distance from the first floor to the next floor) into equal parts, with every part more than 73/4 inches (the maximum height allowable each International Residential Code, or IRC).
Next we’ll want to establish the general length of the stair, also referred to as the carriage or total run. In our example that will be 140 inches. Now we all know that we need a space that is at least 36 inches wide (a minimum code requirement) by 140 inches long (and landings at the top and bottom) for your stair. We also know that the angle of the stair will not be too shallow or too steep, so it’s going to be comfy to walk up and down.
Bud Dietrich, AIA
Fitting our toes. Looking in detail at how our stair lays out, the geometry of the treads (horizontal walking surfaces) and risers (vertical bits at the back of every tread) is set. And note that while every tread is 10 inches deep, there’s a 1-inch nosing that offers an overall thickness of 11 inches. This is a cozy dimension for the majority of individuals, as it provides a suitable landing place for the majority of feet.
Bud Dietrich, AIA
Supporting our burden. Now that we have gotten our geometry place and know we comply with the construction codes, we can start to build our stair.
First come the stringers. These are the sawtooth surfaces of the stair that the treads and risers will attach to. While a stringer could be of any material (wood, aluminum, steel, glass, plastic etc.), more frequently than not in residential contruction, it is constructed from wood. By simply taking a solid piece of wood and then cutting out the teeth, we’ll have the basic structure of our stair.
Stringers are typically designed to be powerful enough to support themselves and also the burden of risers, treads and individuals. This permits a stair to”float” away from a wall socket if that is the desired design. Obviously, if the stringers aren’t designed to support all the added weight of individuals etc., make sure they get attached to an adjacent structural element.
Bud Dietrich, AIA
Next come the treads and risers. Once these are in place, you will have a finished stair that can be used to go from one level to another.
An important design consideration is whether or not the treads and risers must be visible surfaces or even whether these bits will be coated with an end (tile, stone, carpeting etc.). For example, you can save yourself a little money by employing utility-grade timber for the treads and risers.
Bud Dietrich, AIA
Preventing falls. While the stair is complete, our friend Bob can’t make his way down it safely until you can find railings. On the open side of the stair in addition to at the second-floor landing, there should be a guardrail (not shown) that will stop Bob from falling into the ground below.
Another railing that will be needed is a handrail adjacent to the wallsocket. The design, size and position of the railing is regulated by building codes.
Bud Dietrich, AIA
Particularly, the rail can’t be greater than 38 inches or less than 34 inches above a tread (or walking surface), and must be extended horizontally at the top and bottom.
Another code consideration is the requirement to provide at least 80 inches of headroom above any surface. Just remember this, the elevation of a standard residential doorway, is the minimum; as such, I have always found it to be very constricting.
Photos: See these components in tens of thousands of stairway layouts