How to Build Stairs
How To Construct a Staircase, Step by Step
By Doug Adams
The first thing a DIY stair builder should learn is 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 makes perfect sense for stairs that will be covered with carpet. A carpenter-built stair can be dressed up with a hardwood or paint-grade skirt board, and a 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.
The construction materials that you use will dictate the outcome of your finished product, and quality materials will produce a quality job. Don’t mistakenly think that if you plan to cover the material with carpet, the quality of construction materials doesn’t matter; it does. A lower grade of material that contains knots and voids may cause the stair framing to crack 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, grab a pencil and commit your plans to paper. Sketch a rough blueprint of your staircase.
For the purpose of this example, this project will be a straight stair. The building code we are implementing for this project requires 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 head-room to accommodate the stairs. Headroom is very important; you need to be able to ascend and descend the stair safely without smacking your forehead. Many a stair has been torn out due to incorrect calculation of this item before the stair was built and installed. 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 ft., 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 tread — 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 in.) 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 (12.542) is the number of treads needed in the clear opening to make headroom. This would mean 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.
Cutting the Stair
Now that we have directions on paper as to how to build our stair, it is time to begin cutting. Carpenters always measure twice and cut once, a good rule to follow when cutting stairs. Stair building can be expensive; you only want to purchase the materials once.
When you start the project, make sure your work area is clean and well lighted. Lay out the stringers by setting the rise and run of the stair on a framing square. The framing square clamps should be adjusted to 7-3/8 inches by 10 inches.
Next, mark off the number of treads and risers needed for the stair. Always start with the bottom riser and end with the top riser, and draw in the second-floor line. At this point, count the number of risers to ensure there’s no layout error. Repeat this procedure for all three stringers.
After you have marked the treads and risers, make any final adjustments to the stair stringers. In order for all of the risers to be in code-compliance, it might be necessary to adjust the top and bottom risers. In our example, when a 1-inch-thick tread will be added to the bottom tread cut, our bottom riser will be 1 inch too high. The opposite is true at the top. When we add the top tread, its thickness deducts 1 inch from the exposed riser height. To correct this situation we will deduct 1 inch from the bottom riser cut at the floor-level portion of the stringer.
After you have successfully laid out the stringers, cut off the triangular portions. A power circular saw is the best tool for this task, but be careful not to cut beyond your marked layout lines, which will weaken your stringers. The final cutting of the triangles can be cut out with a handsaw or jigsaw.
Note: Before cutting all three stringers, it’s a good idea to “dry fit” the first one you complete inside the stairwell to make sure you’ve made no errors that need to be addressed.
After all three stringers are cut out, place them together to make sure they all match. If you have anything less than three perfect stringers, you may want to go back to the drawing board.
You can now take the left and right stringer and position them on top of the 1×12 skirt boards. On each skirt board, trace the cut where the stringer meets the floor and the top riser. Cut along these lines, and also make a plumb cut on the bottom of the shirt board at the height of the baseboard. Attach the skirt boards to the two stringers. These two stringers are now finished. If no drywall is in place, fill out the stringers to the thickness of the drywall.
Fasten each stringer with a single nail driven through the back of the stringer, then check the fit for level.
The center stringer is now ready to be mounted to the top header and attached to blocking at the floor. (Note: If you don’t have access to the back of the stringers, use a metal hangers to fasten the tops of the stringers.)
Now that your stringers are in place, it is time to double-check all of your cuts. Check the tread cuts for level and plumb. Check your measurements in every direction, left to right and front to back. Do the top and bottom risers allow for the finish tread height? The top riser should offer a tread thickness of more than 7-3/8 inches and the bottom riser should be one tread thickness less. If any stringers are slightly of alignment, shim its bottom level with the others.
After you have double-checked your cuts, nail or screw the side stringers to the studs.
It is now time to rip the risers to the correct heights and nail them into place. Don’t forget to glue and nail them for long-lasting durability. If your treads are 11-1/4 inches, they will not need to be ripped, just cut them to length, glue and nail into place.
Nail the treads and risers to the stringers. Install by nailing through the risers and into the treads using cement-coated fasteners.
Your stair is now complete except for the wall or handrail. Because our example stair is located between two walls, a wall-mounted handrail is required to meet code compliance. Mount the handrail at 34 inches above the leading edge of the tread. It should be 198 inches in length and contain a wall rail bracket screwed into a stud or backing, every 4 feet. In the case of an open rail section to one side of the stair, it is easiest to mount the balusters on an angle cap.
Stair building is an art. Many experienced carpenters have difficulties building stairs. Be patient, and with a little practice, you’ll be making your way up in the world on the steps you’ve just built.
Side Note 1
- To create a softer edge where carpet breaks over the tread edge, route the edge with a 1/2-inch round-over bit prior to installing the treads into the stringers.
- If the material is splitting, predrill your holes. This can also help prevent squeaking in the future.
- Glue blocks can be placed at the underside between the tread and riser intersection.
- Another very important but sometimes overlooked step is to seal the underside of your stair. This will prevent the stair from squeaking and warping.
Side Note 2
Kit-Built Spiral Stairs from Arkè
If you’re looking for a spiral or modular staircase in an easy-to-build kit, Arkè Stairs has you covered with all-in-one complete units. Treads, landing, balusters, handrails, hardware and accessories included. There is nothing to paint, weld, stain or seal, and the kits are in stock for immediate delivery. The standard spiral staircase kit has a 360º rotation, and by adding or subtracting risers, the rotation will change by approx. 30º per riser.
The SKY030 spiral staircase, available in three diameters—47, 55 and 63 in.—is manufactured in steel with a particular treatment (Sendzimir process), which consists of galvanizing steel using a small amount of aluminum in the zinc bath to produce a coating with essentially no iron-zinc alloy. This process guarantees high resistance and durability. In addition, the metal is powder coated. The final result is a staircase specifically made for outdoor installations because of its resistance to atmospheric elements. The landing platform for the spiral staircase is a triangular/universal design, and the staircase can be turned in either a clockwise or counterclockwise rotational turn to suit your home. Learn more at www.arkestairs.com.
Side Note 3
Are Floating Stairs a DIY Project
Floating staircases are designed to hide the supporting structure of the staircase, which gives the impression that the stair treads are floating. Floating stairs remove visual obstructions and maximize living space. They can be installed indoors or outdoors, for homes, businesses or remodels. They can be paired with several different types of railing and handrail options—often installed with glass, cable or rod railing. Many of these options come with components that can be hidden in the posts themselves to enhance the illusion of floating.
Instead of being fixed to a substrate on either side of the steps, the stringer (or stringers) of floating stairs supports the staircase from below. Suppliers such as View rail engineer and manufacture each section of your staircase to your specifications and ship it to you clearly marked and labeled to ensure quick assembly on site. You’ll receive your straight stair stringer in one piece, and all the tread brackets will come with bolts, so it’s simple to bolt the entire system together. Although the manufacture of the floating stair is not a DIY job, its installation can be, and a two-person team of DIY’ers should be able to complete the job by following Viewail’s online instructional videos. Learn more at www.viewrail.com.