Building Deck Stairs
If you have plans for a deck that consists of more than one level or will be more than about 15 inches above the ground, it will need stairs. Stairs can be one of the most challenging aspects of a deck-building project. We can remember when, as young apprentice carpenters, the “stair layout and construction” part of our curriculum created both excitement and anxiety for our group of budding carpenters.
We believe that these “stair building butterflies” had a lot to do with the complexity that some stair building projects can present. When it comes to building stairs, you not only need to be a good craftsperson; in many cases it’s a necessity to have a solid background in both math and geometry. However, as you will learn, not all stair-building projects need to be complicated.
There are many considerations that must be made before building a set of stairs. The stair type (the layout or design); the “total rise” (the vertical distance from the origin of the stairs to the top surface); the “total run” (the horizontal distance that the stairs cover from the face of the first “tread” (the surface you set foot on) to the end of the last tread; and the construction method (how the stair parts are to be assembled).
Before running off to you local lumberyard to buy stair material, you’ll need to know a few “stair” terms to make a material list. You already know that the element that you “set foot” on is called a “tread.” “Stringers” support the treads. The “riser” is the vertical board that is located between treads – except in the case of “open-riser” stairs where, as the name implies, no riser is installed. One other term that you might find useful is “landing.” It’s an area at the bottom of, top of, or between flights of stairs. In the case of a deck, a landing can be large enough to be a “mini deck.”
Although the “straight stair” type is among the most popular and easiest to construct, it is one of many layouts. “Open-riser ladder, L-shaped, T-shaped, U-shaped, switchback and winding are some of the other types. You may employ one or more of these types depending upon the lay of the land and/or how elaborate your deck design is.
No sense in skimping when it comes to stair width. Not being small guys we like stairs of ample width – no less than 36 inches and, in some cases, up to 48 inches. For safety’s sake, building code requires that tread and riser dimensions are consistent for the length of the stairs. In general, code requires that a unit rise (the dimension from the face of one tread to the face of the next) not exceed 8 inches. Code also requires that the unit run (the dimension from the face of one riser to the face of the next) not be less than 9 inches. Since codes can vary from location to location, it’s a good idea to check with your local building department.
Code aside, when designing stairs for comfort, a good rule-of-thumb is the sum of unit rise and unit run should be 17 to 18 inches.
Unless you like “bouncy” stairs, we suggest that you build them using three stringers – one at both ends and one in the middle. A stringer consists of one continuous piece of lumber that runs from one level to the next. Depending upon the desired appearance, a stringer can be cut or “notched” in a saw tooth fashion or remain solid. If you will be using a cut stringer, you can cut it yourself or you can often find precut stringers at you local lumberyard. In either case, the treads are nailed to the top edge of the stringer.
If you, like many people, are afraid of making a mistake when cutting a perfectly good piece of wood as with a cut stringer, a solid stringer may be the way to go. Instead of resting on the stringers, the treads are attached to cleats or metal brackets that are fastened to the stringers below the tread. Most do-it-yourselfers find it easiest to work with solid stringers because instead of having to measure twice and cut once all you need to do is measure twice!
In order to maintain the safety and stability of the stairs, it is imperative that the bottom of the stair stringers be placed on a solid, well-drained surface such as a pad of concrete or compacted gravel. If the stringers consist of something other than pressured-treated lumber or redwood, a small piece of either types of this material should be used between the bottom of the stringer and the concrete or gravel to prevent rot.
The stringers should be anchored to the concrete pad using anchor bolts and a pressure treated kicker or a galvanized angle iron bolted to the inside of the stringer. Risers and treads can be constructed out of the same material used for decking.
When planning your deck stairs don’t forget to include a handrail. Though not always required by code, a handrail is practical, it improves safety and can be a bonus when it comes to appearance.
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