Building a stairway on a sloping hill requires finding the exact vertical rise between your starting and ending points. Whether you are pouring concrete steps or framing a traditional wood stairway, calculating the total rise is the critical first step before determining individual riser heights or the total length of your stair run. Fortunately, you can find this measurement without complex surveying equipment by using straightedges, temporary layout posts, and a standard level.
Setting Up Temporary Layout Posts
To measure the elevation drop accurately, you will need to establish fixed measurement points down the hillside. Cut a point onto the end of a few two-by-four framing lumber pieces to act as stakes. Drive the first post into the ground down the slope from your top landing. Secure this vertical post with diagonal bracing stakes so it remains rigid while you measure.
The height of these posts must be manageable. If you install a post that is too tall for you to comfortably reach while standing on an incline, taking an accurate level reading will be difficult. Cut the posts so they sit at chest or eye level, allowing you to easily read the bubble on your level. For longer hillsides, simply use more posts spaced closer together, stepping them down the slope one by one.
Transferring Level Lines Down The Hill
With your posts driven into the hillside in a straight layout line, place a long, rigid straightedge on the top landing. Extend the straightedge out horizontally until it meets the side of your first vertical post. Rest a standard level on top of the straightedge, adjust it until the bubble is perfectly centered, and draw a precise layout mark on the vertical post.
Next, move down the hill. Place your straightedge on the layout mark you just made, extend it to the second vertical post, level it, and make your next mark. Continue this stepping process down the entire slope until you reach a post positioned directly above your bottom landing area.
Calculating The Total Stairway Rise
Once all level lines are transferred, you will measure the physical vertical distances to find your total drop. Measure from your top landing line down to the first mark. Then, measure from the second mark down to the third, continuing until you measure the final drop to the bottom landing.
Add these vertical dimensions together. For example, if your first drop is 58.75 inches and your second drop is 46.25 inches, your total vertical rise is 105 inches. You will use this final 105-inch measurement to calculate your exact individual riser heights. Depending on the steepness of the hill, you may need to excavate dirt away from the slope or extend your stair tread depths to ensure the stairway fits the landscape while maintaining a straight, safe path of travel.
Three Key Tips
Use Screws For Temporary Layout Bracing
Always assemble your layout posts and diagonal braces using construction screws rather than nails. Screws prevent the structural layout from shifting when taking level measurements and allow you to quickly dismantle the two-by-fours without heavy hammering, which could disturb your grade.
Limit Layout Post Heights For Ergonomics
Size your vertical layout posts based on your own height. A seven-foot post might be workable for a taller builder, but taking a precise level reading above your line of sight on an uneven slope invites measurement errors. Keep the layout marks easily within your field of vision.
Maintain A Plumb And Straight Layout Line
Keep your vertical stakes perfectly in line with each other from the top landing to the bottom landing. Using a string line to establish this path ensures that your horizontal and vertical measurements reflect the true geometric path the stair stringers will follow.
Bonus Questions And Answers
Understanding the total vertical rise is only the first phase of the process; applying that measurement correctly ensures a safe, comfortable, and structurally compliant stairway.
What Is The Maximum Allowable Riser Height For Residential Stairs?
According to the International Residential Code, the maximum permitted riser height for residential stairs is 7.75 inches. When you divide your total vertical rise by the desired number of steps, the resulting individual riser height must not exceed this measurement. Consistently maintaining this structural geometry is critical for fall prevention.
How Much Variation Is Allowed Between Individual Stair Risers?
The building code dictates that the greatest riser height within any flight of stairs shall not exceed the smallest by more than 3/8 of an inch. Taking accurate initial layout measurements with a leveled straightedge prevents the cumulative math errors that commonly cause the bottom or top steps to violate this strict safety threshold.
Should Exterior Stair Treads Be Built Perfectly Level?
Exterior stairway treads require a slight pitch to shed water, rather than being perfectly level. Standard building science and code guidelines allow for a maximum slope of 2 percent, which translates to a drop of 1/4-inch per foot toward the nose of the tread. This intentional slope prevents water pooling, which can lead to rapid wood rot or hazardous ice accumulation during freezing weather.
