Double-check that the stair lands where it should. With the final riser and tread cutout dimensions in hand, you’re ready to mark out your test stringer. Don’t get nervous.

"You can absolutely cut a stair stringer if only you only knew the way the math works," my dad once said to me. So, long before I ever had a geometry class, I knew the math behind determining a slope.

In this video of building a large staircase, I show you how I layout a stringer. It's simple math and if you use the right tools, it is quite easy.

It’s called a stair stringer. Calculate the area of the side of the stringer that is facing you. Look for repeated shapes in it. Rhys has 8 of these stringers.