Building Timber Landscape Steps
Existing slopes in the landscape are often too steep to be walked up or down safely. One good solution is to build timber steps. Steps are needed for slopes over 20%, and ramped steps are best for slopes between 10% and 20%.
Amounts, Specifications, and Supplies:
- 6" x 6" treated landscape timbers--for each step, two 4-foot lengths are needed for tiebacks plus one length that is the desired width of the steps. Eight-foot timbers are easily cut in half to produce 4-foot lengths.
- 10" long 3/8" galvanized spikes (nails) -- approximately 6 per step.
- 2" wide 4" x 4" metal angle braces with 3" galvanized lag bolts -- 2 braces per step, 2-4 bolts per brace.
- Saw to cut timbers (chain saw or large diameter circular saw).
- Drill and screwdriver bit to attach angle braces.
- Framing square and pencil to mark cutting line on timbers.
- Sledge hammer for driving spikes through timbers.
- Carpenter's level to level steps.
- Spade/shovel to dig into slope and backfill.
- Begin by building the desired number of steps. This is best done on a flat, level, hard surface. It does not need to be done at the site, as the individual steps can be transported to the site after construction. Using the saw, cut two 4-foot timbers for each step, and one timber the length of the desired step width. Four-foot wide steps are a good choice because there will be less cutting if using 8-foot timbers. Steps funnel traffic, so the wider the steps, the less wear and tear above and below the step location.
- Assemble the cut timbers on the hard surface in the shape of a square "U". Brace the back of each tie-back timber against a secure surface and drive two 10" spikes through the tread timber and into the tie-back timbers as shown below. These holes will need to be predrilled with 3/8" holes. The 3/8" spikes will still fit snuggly in 3/8" holes.
- For extra support, place one angle brace at each 90-degree angle where the timber that forms the step and tieback (the part of the step buried into the slope to anchor the step) timbers meet, and secure it with 3" lag bolts into each timber, as shown in the diagram above.
The timber that forms the step creates both the riser and the tread of the step. The riser is the vertical distance and the tread is the horizontal distance, the portion you step on. In this example, 1/2 of the tread is timber and 1/2 is filled with a complimentary material.
- At the landscape site, begin at the bottom of the slope where the steps are to be installed. Using the spade or other means, dig 4 feet back into the slope to a depth equal to the depth of the step timbers. Set the first step in place, making sure it is level in all directions. The top of the step timbers should be level with the grade of the path leading up to the steps. This first step will not be visible, but will be buried in the existing soil to act as a base to attach other steps. The second pre-constructed step should be placed directly on top of the first step, and attached using six 10" long 3/8" spikes through pre-drilled holes.
- Determine the desired location of the next step up. Typically, outdoor steps are 12 inches deep and 6 inches high. However, if the slope is not that steep, you may want to build ramped steps where the tread is deeper to allow people to take one or more extra steps between timbers. The typical person's step is 24-26" long, and allowing for that distance between steps will allow most people to traverse the steps smoothly. Dig back into the slope as necessary, allowing 4 feet of level space behind the location of the second tread.
- Place the next pre-assembled step on top of the tie-backs of the first step, positioning the tread in the desired location. Be sure the step is level in all directions. Drive a 10" spike through the tread approximately 4 inches from each end, into the tie-backs of the previous step below. Another spike may be necessary 2 feet past the first depending on how long the tiebacks are.
- Continue placing pre-assembled steps on top of each other, connecting them with 10" spikes. Curves in the stairway can be achieved by angling each step as necessary.
- When all the steps are in place, the area inside the "U" of each step can be filled with your choice of material, such as pea gravel, brick pavers, concrete, landscape rock or shredded wood mulch.
This implementation report is based on landscape projects completed by University of Minnesota students enrolled in landscape design and implementation courses, Department of Horticultural Science.