How to Design Stairs for a Tight Space

Identify the maximum amount of room you have for the stairs. Draw the wall or the limits of your space on 1/4 inch graph paper. Sketch in the surrounding wall areas, so you can see how they might impact your design. Measure the height of the walls, and draw an elevation (frontal view) showing the wall height.

Draw a side view of the elevation that is likely to feature the side of the stairs. The side elevation should cut away existing walls, so you can see how the top of the stair would land on the floor level where the stair will reach. Measure away from the top landing line nine inches for minimum tread depth.

Divide the height from the top of the bottom floor to the top of the upper floor by a value between eight to 10 inches evenly. Draw a vertical line from the bottom floor of the side view elevation to this measurement. Draw an angled line from this mark to the top of the upper floor. This is the slope or steepness of your stairs if limited to the space you have indicated.

Measure up from the bottom floor using the same measurement you used for your bottom tread riser height. All your treads should be the same height. Each tread needs a minimum of nine inches (11 is better) for good footing. In a standard staircase, each tread would measure away from your bottom riser. In a constrained staircase, you will be designing the stairs differently.

Measure from the bottom riser edge to the top riser edge. The top riser edge is the point where you will step on the upstairs floor. Divide this amount by the number of treads minus one. This is the measurement for where each riser will start along the slope of the staircase. As you may notice, this will create a tread much too shallow to use. The solution to this problem is that your treads will need to be angled, creating triangular-shaped treads.

Looking at a stair tread from above, the outer (left side) of tread one will be nine inches deep, and the front of the tread will angle at roughly 30 degrees toward the middle. Tread two will be nine inches deep along the right side, and the front of the tread will angle toward the middle at roughly 30 degrees. Tread two will be set back from tread one by the amount in Step 5.

Your calculations of angle might make your angle on each tread more shallow. The more shallow the angle, the more physical tread is available for each step.

Visualize this type of stair by stacking dominoes at angles to match your measurements. This will allow you to understand how the stairs can be constructed as well. This type of stair is a series of rectangular boxes turned at inward angles, where the back of the box becomes sliced off near the top of the staircase as the box runs out of room.