In this posting, I am going to focus on the difficult yet rewarding task of step installation. Step construction is a lot more challenging than most people realize. Whether it be inside or outside, out of wood, block, concrete or natural stone; we all use steps to get us from a lower elevation up to a higher point. My goal in this issue is for you to at least have a greater appreciation for the amount of craftsmanship required to create a successful set of steps.
Constructing a set of steps requires a lot of patience. There is a lot of figuring required and you definitely can’t be in a hurry when you build them. The key to successful steps is having uniform vertical and horizontal increments. The vertical distance in a set of steps is known as a riser while the horizontal part that you step on is known as a tread. As you walk up a set of steps your body subconsciously trains itself to lift your legs the correct height and distance as you climb. Therefore, if your risers and treads are not uniform it creates awkward footing which can lead to dangerous falls.
The first challenge in constructing a set of steps is calculating how many steps will be needed for a given elevation change. To do this you must measure the upper and lower surface elevations and figure out the grade change. A laser level or transit should be used to achieve the most accurate readings. When doing this, it is important to make sure that you know exactly where the lower or upper elevation will be. There is often a lot more than just the steps going on within a project. For example, the steps usually land on a patio or walkway so you need to know the final surface elevations of that feature all the way down to the base depth so that everything ties together upon completion.
Once you have determined an accurate grade change, then you need to divide through by your desired riser height to find out how many steps you will need. The average riser height for exterior landscape steps is between six and eight inches. So, as a simple example, if you have an elevation change of thirty inches and you would like to have six inch risers, you will have to build five steps. Often times, the product you are using will determine what riser heights you are limited to during construction. Riser heights tend to vary among natural stone steps but the key is to keep them as uniform as possible throughout the structure.
The depth of the treads (horizontal increment) must also be considered when designing a set of steps and can directly affect the riser heights. In most cases, you have plenty of room to build steps but if you only have a small area to work with you will either have to increase your riser height or shorten your treads or both to allow them to fit. Step treads should be a minimum depth of eight inches but for most landscape situations I prefer twelve or ideally fourteen inch treads. Nice big treads produce a grander set of steps that are easier to maneuver. Once again, uniformity is the key to safety. Depending on the grade, I often include a platform between sets of steps; this slows down pedestrian traffic and makes the steps easier to navigate.
After you have decided your quantity of steps, you must lay the structure out based on tread lengths, platforms, and overhangs. The distance that a tread extends beyond the riser is known as an overhang. I normally recommend an inch to inch and a half overhang for the best aesthetics. It is important to factor in this overhang because it will affect the overall length of the structure.
Everything is now laid out and it is time to start building your steps. Where do you begin? Like everything else, the base is the most important part of any set of steps that is going to withstand the test of time. There are three different methods of base installation that I use when constructing steps. For most segmental block steps that are being constructed on sites with free draining soils that have been allowed to settle for a least a decade (established homes), I usually recommend having a minimum base depth of twelve inches. This base should consist of crusher run gravel (ASTM 2940) and should be compacted in lifts on top of a woven geotextile fabric.
I use a different method for constructing a step base on newly constructed homes and sites with clay soils. Steps built in these site conditions are often susceptible to failure due to settling and frost movement within the base. For these sites, I recommend excavating down below frost level, a total depth of forty eight inches. I then fill the cavity up with angular drainage stone (ASHTO 57’s) to within six inches of the top. This angular gravel material is 96% compacted as soon as you place it in the hole which when combined with compaction eliminates any risk of settling. Next, a six inch thick slab of concrete is poured and reinforced with wire mesh. This process creates a frost-free base that is no longer susceptible to frost or settlement. My company now uses this method for every set of steps that we construct against a foundation.
The third method of step base construction I use applies to step treads that lead up natural embankments. This form of steps involves large individual pieces known as treads. In my area we usually use bluestone, limerock, or granite for these steps because the stone is indigenous to our region. For this type of step, I recommend excavating one foot of soil for the initial step and installing a woven geotextile fabric. I then use a jumping jack compactor to compact angular drainage stone (ASHTO 57’s) at a minimum depth of nine inches. The first tread is then placed with a machine and backfilled with more drainage stone, maintaining a minimum compacted base depth of nine inches. Each step is laid on top of the next using the same procedure until the final elevation is reached. This is a very effective way to create a profound set of steps in a short amount of time. During our last project, my company was able to construct a set of five Techo-Bloc Maya Steps in one hour with a three man crew.
Once your step base has been created, then you step construction can begin. It is critical that you take your time to make sure each individual piece is level and tied in with the piece beside it. To re-enforce this new structure, I recommend adding bi-lateral grid to each layer which greatly strengthens the overall unit. Another technique I use when building steps out of segmental wall block is I actually frame in the entire unit with wall block rather than just filling the inside stone against the foundation. This strengthens the structure creating an independent step unit as well as prevents any detrimental moisture from reaching the foundation of the residence. Taking all of these extra measures greatly increases the cost of construction but I can tell you from experience that doing it right the first time is much less costly and mentally taxing then doing them over!
There are few things you must consider when building steps such as the local codes. Many towns require railings depending on where they are located and how many steps there are. We often build walls into steps to act as railings or add wrought iron railings when we are finished. Another thing to consider is the shape of steps. I continually discourage clients from having circular steps. Although they look fantastic, they not only create more work but are not very safe to climb. When you think about it, everywhere you step on circular steps, the step below is at a different angle than the one prior, making the potential for falling very high. The last thing to consider when designing a set of steps is lighting. There are many low voltage light kits available that can be incorporated into a set of steps for aesthetic purposes as well as safety. All of these things must be decided before you begin construction so that the necessary preparation can be made.
I apologize for this lengthy post, it is further evidence that step construction is much more involved than many people realize. Building steps is a very slow yet rewarding process. There is a great feeling of accomplishment when you reach the final step and complete it. If everything has gone well, you can look back on a beautiful set of steps leading to and from a patio or up a hillside. The next time you climb a set of steps please take a minute to appreciate the amount of hard work and figuring that went into their creation!
Post taken from Jerry’s quarterly “Hardscape Column” for Nursery Lines Magazine; Fall 2012 NYSNLA