How to plan a staircase gallery wall

Rise is the vertical height of one step; run is the horizontal depth of one tread. Measure both across several steps and divide, rather than trusting a single step, because the bottom and top steps in a flight are often slightly different from the ones between them. Residential rises commonly land between 7 and 7.75 inches and runs between 10 and 11 inches, but measure yours instead of assuming.

Be consistent about the nosing. If you include the tread overhang in one measurement, include it in all of them, because a 1-inch inconsistency repeated across ten steps moves the top frame by 10 inches. Record the step count for the flight as well; the tool uses it to check that your sequence of frames does not run past the measured horizontal run or the measured total rise.

The angle of the baseline your frames will follow is atan2(rise, run), converted from radians to degrees. A 7.5-inch rise over a 10-inch run gives 36.9 degrees. A 7-inch rise over an 11-inch run gives 32.5 degrees. That difference of four degrees sounds trivial until it is multiplied along a 100-inch run, at which point the top frame centre is out by more than 7 inches.

The related number is the step diagonal, hypot(rise, run), which is the distance along the baseline that one full step covers. For a 7.5 by 10 inch step that is exactly 12.5 inches. Knowing the step diagonal makes spacing decisions concrete: a 12.5-inch spacing puts one frame per step, and a 15-inch spacing deliberately drifts out of step with the treads.

Do not rotate the frames. Each frame stays level to the floor, and it is the line joining their centres that follows the stair pitch. Tilted frames look like a mistake from the landing, they fight every other horizontal in the room, and the mats inside them stop reading as rectangles. The rising baseline supplies all the diagonal energy the wall needs.

Mechanically, each successive centre advances by x equals direction times cosine of the angle times distance, and y equals sine of the angle times distance. At 36.9 degrees with a 14-inch along-baseline spacing, that is 11.2 inches across and 8.4 inches up per frame. Those two numbers, not the 14, are what you actually mark on the wall with a tape and a level.

Ascent direction is simply which way the stair climbs as you face the wall. Left-to-right advances x positively while y rises. Right-to-left reverses x while y still rises, which is the case that catches people out on paper and produces a mirrored plan that will not fit the wall. Set the direction in the tool before you place anything, not after.

Pick the direction by standing where the wall is actually seen from, usually the bottom of the flight or the hall it opens off. If your stair turns, the two flights may ascend in opposite directions relative to the viewer, and each flight then needs its own baseline and its own direction setting rather than one continuous line drawn through the turn.

Every other position is derived from the first centre, so choose it deliberately and mark it physically. Pick a step you can identify again, measure horizontally from a fixed edge such as the wall corner or a door casing, then measure vertically from the nose of that tread. Enter those two values as the reference point and the tool generates the rest of the sequence from them.

A sensible datum height is 57 to 60 inches measured vertically from the nose of the tread directly below the frame, which keeps every frame at a comparable height for someone standing on the stairs. Starting too low at the bottom of the flight is the usual error: it looks fine from the hall and then the top frames end up near the ceiling.

Spacing on a stair wall is measured centre to centre along the sloped baseline, not across the floor. Twelve to 16 inches suits most flights with 8 x 10 and 11 x 14 frames. Convert once to check the visible gap: at 36.9 degrees a 14-inch along-baseline spacing between two 11-inch-wide frames leaves a horizontal gap of only 0.2 inches, so widen the spacing or narrow the frames.

A landing is a break in the baseline, so treat it as one. Run the rising sequence up to the last tread, then start a level run across the landing wall at the height the last stair frame reached, and begin a new sloped baseline for the flight above. Widen the gap at each junction by roughly half a normal gap so the change of direction reads as intentional rather than as a spacing error.

Marking a stair wall means standing on an unequal surface with both hands occupied, which is the actual risk in this project. Use a platform or ladder designed for stair use with levelling legs, set up according to its manufacturer instructions, and never place a foot on a tread nosing. Move the equipment rather than reaching sideways, work with a second person, and keep the flight clear of tools and offcuts between marks.