Stairs & Railings

Pencil & Paper Stringer Layout

Step 1 - Calculate The Rise

• Divide Total Rise By Maximum Riser Height - Before you can begin calculating your stair stringer layout, you'll need to measure the "total rise". For stairs that land on the ground, the total rise is the distance from the ground to the top of the finished floor. Once you know the total rise, divide this number, by the maximum allowable riser height. According to International Building Code (IBC), the maximum riser height is 7-3/4". (Other codes limit the maximum riser height to 7".)
   
  Note: You don't have to use the maximum allowable riser height. If you look at the Rise & Run table on the following page, you may elect to use a smaller value for your maximum allowable riser height. For example, if your knees just aren't what they use to be, you may elect to reduce the riser height to 6".
    
• Always Round Up Gives Number Of Risers - For this example, we'll assume the total rise from the ground to the top of the decking is 53". Since I personally don't like risers any taller than 7", I divide 53" by 7 and get 7.57. Always rounding up gives me 8 risers. At this point, I now know that my steps will have eight risers. By the way, even if the total rise had only been 51" and I divided by 7 to get 7.29, I would still round up to 8 risers.
   
• Dividing Total Rise By Number Of Risers Gives Riser Height - Now that we know how many risers the stairs will have, divide the total rise by the number of risers to get the actual riser height. For my example, I divide 53" by 8 to get a riser height of 6-5/8".

Check Point - It's the lower part of the stair stringers, below the notches, that carries all the weight. It's important to size the stringers based upon the total stair run, the width of the stairs, the type of stringer, and the number of stringers. When you get a password, we'll help you to select the right size stair stringers for the job.

Step 2 - Calculate The Tread Run

• Determine The Number Of Treads - If you're building stairs that place the uppermost tread one step down from the deck/floor then the number of treads is one less than the number of risers. If your stairs have the top tread level with the deck/floor then the number of treads is equal to the number of risers. Since the stairs in my example have two or more risers and are over 30" high, by IBC code, I'm required to install a handrail and railing. Knowing this, I'm going to elect to place the top tread one step down since this will make it easier to install the handrail - won't require additional posts to prevent the stair railing from overshooting the deck guardrail. So for this example, I know there are 7 treads.
   
• Dividing Total Run By Number Of Treads Gives Tread Run - In this example, since the stairs are used outdoors and extend to the ground, the stairs don't need to have a specific total run. In this case, a standard tread run of 10" is selected. This is a good tread run because two 2x6 boards laid side by side add up to 11" which will give a comfortable 1" nosing. Looking at the Rise & Run table on the following page, we see that a rise of 6.625" and a tread run of 10" produces a nice 33.5° stair angle so we're all set; the tread run is 10".

Check Point - The area of the deck where the stairs connect must be reinforced to handle the weight from the stairs. You don't want the framing to fail if there is an emergency and a lot of people fill up the stairs. The amount and type of reinforcing depends on the location where the stairs attach. There are four different types of reinforcing approaches (depending on whether the stairs attach to a side or end band joist and whether the joists are cantilevered). When you get a password, we'll teach you how to add extra stair reinforcing so your deck is strong enough to support the heaviest of stair loads.

The content under the "How-To" menu is a small sampling of all the material covered on BestDeckSite. For immediate access to in-depth information on Building Codes related to stairs and railings, an on-line Stair Calculator, selecting the size of lumber for the stringers, and intermediate landings, as well as, comprehensive coverage of all aspects of gazebo and deck building, get a password and log-in now.

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