The Denver Single Stair Competition (2025) explores ideas for changing the International Building Code to allow higher density residential buildings up to six stories with a single stair for access. (This is in contrast to the current code which allows four units per floor up to three stories.) Changing the code would replace the need for a second exit stair, and avoid the ubiquitous corridor accessed model with its single aspect units. Single Stair access would allow higher densities on small infill parcels. Dwelling units could be double aspect to allow for cross ventilation. Up to four units around a stair creates the opportunity for a more sociable community in place of the anonymous corridor. It is the model for most countries outside of the US. Several cities such as Seattle are already permitting Single Stair access up to six stories. This competition is an important part of the campaign to change codes.