Tiny House Loft Stair Calculator & Appendix AQ Math Guide
- Appendix AQ relaxes standard stair requirements specifically for tiny homes under 400 sq ft — regular code would eat up too much floor space
- Riser height must fall between 7" and 12" — steeper than a standard home but safer than a ladder
- Two formulas link riser height and tread depth — which one you use depends on whether your height or your floor space is the fixed constraint
- Ceiling under 6’2" at the loft entry? Code requires a landing platform — in a tiny home this almost always applies
- The calculator below handles all the math including subfloor adjustments and landing platform riser, to 1/32" precision
If you’re building a tiny home with a loft and want to pull a permit, your stairs need to meet Appendix AQ of the International Residential Code. This is the section added specifically for tiny homes under 400 square feet. It relaxes the standard stair requirements — regular code would eat up too much floor space in a small build — but you still have to follow specific formulas for rise and run.
This post walks through how the math works and includes a calculator that handles all of it for you.


























