How to Build Stairs—A DIY Guide
How To Build Stairs a Step-by-Step Guide to Constructing Staircases
How to build stairs? There are two different classes of stairs. The first class is a mill-made stair, which is usually fabricated in a mill shop and shipped to the job site as a kit, ready for assembly and installation. The second class, a carpenter-built stair, is just that — a stair built on site by a carpenter. This type of fabrication is less expensive and allows the stair to be covered with carpet. A carpenter-built stair can be dressed up with a hardwood or paint-grade skirt board. And simple wall-mounted railing is a popular option to complete either type of stair.
When building a stair, functionality is the most important consideration. Extreme accuracy must be used for a safe design. Before beginning construction, you should consult not only the national building-code requirements, but also the local building-code requirements. Some municipalities have stricter codes than others, and checking first will eliminate the need to rebuild later.
After determining the correct code requirements for your stair, consider the stair’s design aspects. Remember, the construction materials that you use will dictate the outcome of your finished product, and quality materials will produce a quality job. Do not mistakenly think that because the material will be covered with carpet and no one will see it, the quality of construction materials doesn’t matter; it does. When you use a lower grade of material that contains knots and voids, the stair may encounter cracking at a later date. Most lumberyards carry stock used specifically for the construction of stairs.
Layouts and Calculations
After you have determined the proper codes to follow for your municipality, you are ready to begin the layout and calculations of your stair. Grab a pencil and commit your plans to paper, sketching a rough blueprint of your staircase.
For the purpose of this example, this project will be a straight stair. The building code that we are implementing for this project is BOCA 96 for residential use. This code states that you may have a maximum riser height of 7 3/4 inches and tread run of no less than 10 inches.
First determine the size of your stairwell, making sure to allow for the proper headroom to accommodate the stairs. Headroom is very important; you need to be able to ascend and descend the stair safely. Many a stair has been torn out due to incorrect calculation of this item before the stair is built and installed. There is nothing worse than having some common stair-building sense knocked into you by bumping your head. For this example the nosing will be a standard 1 1/4 inch, the tread run will be 10 inches each, and the headroom will be 6 feet, 8 inches.
Assuming the distance from one finished floor to the other (total rise) measures 118 inches, find out the number of risers needed by dividing the total finish rise by 7.5. The resulting number equals the number of risers. Then divide that number into the total finish rise.
Example: Total rise 118”/ 7.5 = 15.73 — round up the total number of risers to 16
Total rise 118”/16 risers = 7 3/8” each rise
Knowing the number of risers tells you the number of treads — 15 (the sixteenth riser will be positioned approaching the upper floor with no tread on top). The run of the stair will then be 15 treads at 10 inches per tread, or 150 inches of total run. To determine the actual total length of the stair, you must add the nosing of the bottom step and the thickness of the top riser.
Example: Total tread run 150” + 1 1/4” nosing + 3/4” top riser = 152” total stair length
Next, calculate the length of the stairwell, or the width of the upper floor’s vertical shaft in which the stairs are located. This is a two-step calculation.
First, account for the required headroom and the upper-floor construction, including floor-joist height, floor thickness and drywall thickness. For the purpose of our example we will calculate the upper-floor construction to be a total thickness of 12 1/2 inches. This figure (12 1/2 inches) added to the desired headroom height of 80 inches will total 92 1/2 inches. Take this dimension and divide it by the riser height.
Example: 92 1/2” / 7 3/8” = 12.542
The answer you get (12.542) is the number of treads needed in the clear opening to make headroom. This would mean that you now have 2.45 treads that are located under the header. By multiplying 12.542 (number of treads in clear opening) by 10 inches (tread depth dimension) and adding 1 1/4 inch for the nosing and 3/4 inch for the top riser, you will achieve the stairwell length needed for the proper headroom. The result for our example is 127 7/16 inches for stairwell length. Most stairs that are located between two walls have a finished width of 36 inches. To accommodate this finished width you will need to make your rough opening 37 inches.
The end result of our layout procedure is: 10” run, 7 3/8” rise, 127 7/16” stair well length, 37” stair well width, 36” stair finish width.