HOW TO CUT YOUR FIRST SET OF STAIRSTABLE OF CONTENTS
INTRODUCTION NECESSARY TOOLS MEASUREMENTS AND CALCULATION LAYOUT THE CUT ATTACHMENT COMPLETION INTRODUCTION
Having spent the last 30 years in the residential framing business, I have determined that the two aspects that cause the most anxiety are stairs and roofs. Probably because there isn't a lot of room for error and there is some math involved. There are more calculations involved in working with roofs but both use the same basic concepts. Putting in a set of stairs is not as difficult as it is at times portrayed. With a few measurements, calculations, and the right tools you can easily cut and install a set of stairs In the following pages I have tried to provide step-by-step information so that you will be able to build your stairs, but first there needs to be some clarifications. I have chosen to illustrate a simple set of steps appropriate for a deck as a starting place. Although the stair systems used in houses are based on the same basics there are many more variables that need to be dealt with. Before we get started there are some building codes that need to taken in consideration: 1: The maximum rise is 8 inches. 2: The minimum run is 9 inches. 3. You can only have a maximum of 3/8 of an inch total variation in the stair system. The whole purpose of these codes is "trip" prevention. Have you ever gone up a flight of stairs and something just didn't feel right? Amazingly, it takes only 3 steps for your body to set a pattern. After that pattern is set and if there is too much variation you can "feel" it.
1. Framing Square: There are 3 basic squares available and like everything else they have positives and negatives. The steel square is durable, however it is a little heavier and will rust if left out in the weather. The aluminum square is lightweight and won't rust, however, it gets bent easily. The magnesium square is the most durable and rigid but also the most expensive. Any of these will be appropriate for our needs. 2. Power Saw: Any good power saw will work as long as it has a sharp blade. 3. Tape Measure 4. Sharpened Pencil: This may seem a little obvious but none the less important. We don't want to try to cut along a line that is 1/4" wide. 5. Cutting Platform: A solid set of sawhorses will do the trick here. 6. Stair Jack Guides: This is a set of two guides that attach to the framing square. Set one guide for the run and the other for the rise. 7. A 4-foot level will be useful but not mandatory.
We want to maintain around 7 1/2" for the rise so let's assume the deck is 60" high. Divide 60" by 7 1/2" and the result is 8. We now know that there will be a total of 8 steps, however we only cut 7 rises because the last step will be the one onto the existing deck. Since the normal run is 10" (minimum is 9") we know the stairs will start approximately 70" out from the deck. Now that we know our rise and run we can start the layout. We will need a 2x12 long enough for our purpose, probably 10 foot. We want a board with just a little crown in it (1/8" to 1/4" crown will work). We want a little crown in the board so that the stairs don't sag. We also want one with tight knots and no cracks down the center of the board. Nothing is more frustrating than to have your jack break right after you have it cut and ready to install. Next, set the stair jack gauges on the square at 7 1/2" and 10". See figure 2.
figure 2
Now start laying out the stairs moving the square down the 2x12 and marking the board. Once that is done, making sure there are 7 steps, the adjustments are next. From the bottom step subtract the thickness of the tread material. Depending on your choice of material, this can be anywhere from 3 1/2" (4x12) to 1 1/8" pre-made tread material (not recommended for outdoor applications). If the bottom of the steps is sitting on concrete it will be necessary to create a means of securing the bottoms so they don't move. To accomplish this, make a 3 1/2" by 1 1/2" notch in the bottom. See figure 3.
This allows us to place a pressure treated 2x4 under the nose of the jack. We will deal with this a little later.
It's now time to cut our jacks. It is permissible to over cut, however, it you want to produce a nice finished product use a jig saw or hand saw to finish the cuts. Once this is completed, it should look like figure 4 only with 7 steps.
.figure 4 Notice the 2x4 attached to the side. This is the jack stiffener. It is nailed to the side in order to strengthen the jack and help keep if from breaking and/or sagging. I've found the easiest way to make the stiffener is to position a 2x4 on the jack and simply scribe and then cut it. The width of the stairs will determine how many jacks to cut. Two foot on center is the maximum span you want for a jack, so 3 jacks will give a 4-foot wide stairs. If you're going wider than that then you need to cut more jacks. Use the first jack that you cut for a pattern for the remaining jacks. Before attaching the jacks, I suggest putting a couple coats of stain or paint on the jacks, paying the most attention to the bottom cut. The stain will help stop moisture from penetrating the cut sections of the board and deter dry rot.
We're almost done so let's start putting the pieces together. Now we have to determine the starting point for the first jack. Locate the point on the deck that sets the outside of the stairs. See figure 5.
Attach the top of the jack making sure that we maintain our 7 1/2" rise and the stiffener is to the inside and not visible. Now that the top is secure we want to square up the stairs with the deck. There are 2 basic ways to accomplish this. The easiest way is to take the framing square and place it in the corner and moving the jack side to side so there are no gaps between the deck, jack, and square. If you want to be more accurate then use the 3-4-5 approach (see Pythagorean Theorem). Since we know we're coming out 70" the closest number the 3-4-5 sequence is 51"-68"-85". This is achieved by multiplying 3-4-5 by 17. Now, measure to the side 51" and out toward the end of the jack 68". Move the jack side to side until the diagonal measurement is 85". The stairs are now square with the deck. Locate and nail the tops of the other jacks making sure to use galvanized nails to prevent rust. Once the tops are secured cut the pressure treated 2x4 to length. It should be the same length as the stairs are wide, so if our stairs are 48" wide we want the 2x4 to be 48" long. Slide the 2x4 into the notches that were cut. I have found that putting a bead of adhesive between the 2x4 and the concrete helps maintain the security of the bottom of the stairs. Nail the pressure treated 2x4 down with fluted concrete nails. A concrete power nailer works best if one is available. Now attach the bottom of the jacks, again using galvanized nails, to the 2x4. Make sure that the layout at the top and bottom are the same. Cut and nail the treads and CONGRATULATIONS! YOU HAVE STAIRS!
I hope this was helpful.
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