Stairs are one of the many things we take for granted in our homes, unless you've got one of those grand entryways like we're used to seeing in movies like Gone with the Wind. Stairs are an integral part of any home with more than one level, giving us access to upstairs along with the attic and/or basement.
We're able to take stairs for granted because of the building codes which control how they're designed and built, making them safe for us to use and often, abuse in our chaotic lives. Fortunately houses come with stairs so when exactly do you need to design stairs?
Designing Stairs – When and Why
The most common reasons for designing and building new stairs include:
- Finishing your attic or basement when there are no stairs, i.e. all you've got is an opening in the ceiling.
- Builder stairs to the attic don't meet current building codes. Many homeowners learn this after they've spent their remodeling budget, so before ordering flooring, identify changes needed to bring stairs “up to code”.
- Another remodeling project requires moving stairs to gain needed space.
- Occasionally stairs are the focus of a remodeling project, typically when they're in the center of the house with walls on one/both sides. By redesigning the stairs and opening them up to one/multiple rooms, you can create today's popular open concept without adding square footage to your home.
- Stairs in older homes may need significant repairs and new stairs might be a better option.
Stair Design and Building Codes
In the US, each town has different building codes. Most town codes are based on either the 2000 or 2003 International Residential Code (IRC), with changes to address local concerns like flooding or hurricanes. Like smoke detectors and energy efficient building codes, there are reasons why each item is included in the IRC. For residential stairs, the primary focus of building codes is safety. A difference of just 1/4 inch between 2 steps can cause an accident so it's important that stairs are built uniformly, with every step the same height and depth (learn more about stair safety in this report by Cornell University).
- Stair width has a minimum of 36 inches, and allows for wall mounted handrails to project 3 1/2 inches from each side.
- Stair risers are the vertical front of each step (may be open for deck stairs) and their maximum height must be between 7 3/4 and 8 1/4 inches, from the top of one tread to the top of the next tread. Some states also have a minimum height of 6″ which can be a significant hurdle when restoring old buildings with marble stairs, because they don't meet these height requirements.
- Stair nosing (what you might guess) is the part of the tread that extends out past the riser below it. The maximum overhang for nosing is between 1 1/4 and 1 1/2 inches and some states legislate a minimum of three-quarter inches.
- Stair treads are a bit more confusing as there are really 2 measurements involved. The “stair run” refers to the distance from the front of the nosing to the front of the nosing on the next step. The minimum run is between 9-10″ and when you add in the part underneath the nosing of the tread above, you get the width of the stair tread. For example, a stair tread with a run of 9 1/2 inches plus a nosing of 1 1/4 would be 10 3/4 inches wide.
The information here isn't intended to help anyone design a set of stairs. The goal is to help explain the intricacies that go into designing a house or remodeling project. There are many more decisions that go into stair design, i.e. we haven't talked about the railings which include a combination of newel posts and balusters. Building codes also define the height of stair railings along with spacing of spindles, to prevent a small child from getting their head stuck (4 inch maximum opening between spindles).
Carpenters who build/install custom stairs are master craftsman who tend to specialize in this niche. I personally watched one carpenter take 4 or 5 days to install the newel post at the bottom of my new stairs (custom stairs were build at the factory). They are more like cabinet and furniture makers who focus on incredibly minor details to assure the final product comes out right. With so many articles online suggesting a diligent do-it-yourself homeowner can build their own stairs, I disagree and encourage you to find someone who's already built at least a dozen staircases.