One of the hardest things to do in carpentry, besides laying out hip roof rafters, is laying out stair stringers. Mostly because there are only one set of stairs in a house and that today most stairs are purchased pre-built and just have to be set in place. Young carpenters have forgotten the lost art of stair layouts. Hopefully this project will give you the knowledge you need to replace old, sagging steps, or steps that were always a little off from the moment they were installed.
Wood
For this exterior project, you should use pressure-treated lumber. Although this is not the most attractive choice, it will last the longest. Other types of wood that can handle the weather are redwood and cedar, but they are expensive and not as strong. They also have a tendency to split, especially when you consider that half of the material will be removed in deep notches. The better alternative is to clad the stringer with a high-quality cedar and use solid mahogany deck boards for the treads.
Layout
The layout will tell you how many risers are required and the vertical distance between them. It is best to use a piece of graph paper to help lay out the steps.
1. Measure the distance between the deck or finished floor and the sidewalk surfaces. This determines the rise of each step. The distance from the deck surface to the floor, sidewalk or deck surface below is called the total rise.
2. Determine the thickness of stair tread material. Usually this is 1 inch for 5/4 deck boards.
3. Lay out the heights of the top surface of the stair treads. This may sound like overkill, but you have to make accurate cuts in the stringer. If you cut the boards with the riser heights, the top tread will be an inch higher where it meets the deck surface. This is where a lot of people just trim the bottom off the stringers and call it a day. This makes the first step an inch lower than the rest.
4. Subtract the thickness of the stair treads to determine the horizontal cut lines that will be marked on the stair stringers.
5. Determine a starting point for the front surface of the risers. On many decks and porches, the top riser will determine the starting point, because the top riser is left off and the outer joist of the deck structure is used.
6. Determine the tread widths. It is important to determine the location of the front edge of the first tread. Common tread materials for exterior decks are; 2- 5/4×6 deck boards, which will add up to about 11 inches, 2- 2×6 boards will provide a width of about 11 inches, A 2×12 which gives a tread width of about 11-1/2 inches., or a 2×10, which gives a tread width of about 9-1/2 inches. Widths of 9-1/2 inches are good for indoor treads, but 11-plus inches is best for outdoor steps.
7. Subtract the overhang distance to get the location of the front of the next riser. The overhang is usually one inch, but distances of 3/4" to 1¼" are also acceptable.
8. Subtract the riser material thickness to get the vertical cut line for the stair stringers. Risers are usually 1×4’s or 6’s that are about ¾ inch thick. Many designs omit the riser boards. If you use the 5/4 decking for the riser board, you will have to subtract 1 inch.
9. Continue the sketch for the other treads and risers.
10. A framing square in the best tool to lay out squares, since the corner will be the point of the notch for the cut. The scale on the square starts from the point so it’s very easy to transfer the dimensions to the stringer. You can also purchase stops that clamp onto the square for long stairs where you can have more than 12 risers. They are called brass stair gauge clamps, but are commonly referred to as “bugs". You can purchase a set for $5 to $10 at any home center or hardware store.
11. Transfer the measurements to your pressure-treated 2 x 12 stringers. For a standard 4-foot wide step, you will need two stringers. For wider steps, go with three stringers. The hard part is done with the layout.
12. Use a circular saw to cut the stringer notches to about 1 1/2 inches from the vertex of the notch. Finish the cut with a hand saw.
Shaded areas show removed material
13. Cut the tread boards to the proper length; you should have the treads overhang the stringers by about 3/4 of an inch on each side. This is for aesthetics, but if you are wrapping the stringers with cedar or some other wood, make sure to add the thickness for the board and then add the overhang.
14. Pre-drill all holes for the treads and use stainless steel deck screws for attaching the boards to the stringer.
15. Screw a board in between the stringers flush with the back edge. Use galvanized lag screws or carriage bolts and attach the steps to the rim joist of the deck or porch. You can also attach a cleat to the porch or deck for the stringer to rest on for added support.
16. If your steps have more than 2 risers, you will need a railing. Check with your local building department to see what the requirements are.
Example:
The distance between your sidewalk and porch is 27 inches. Start with a riser of 7 inches and divide 27 inches by 7. This gives us 3.8 steps, so we round it up to 4 risers.
27" divided by 4 gives a riser height of 6.75 inches. Risers should be between 6 1/2 and 7 1/2 inches so adjust the number of risers to get within that range. Use 10 inches for the tread width, or run, with a one inch overhang.
Building your own steps is a rewarding project that any homeowner can tackle with the proper instructions and measurements.
