Upon his master's degree in 1992 he founded M3H architecten, Amsterdam, of which he has remained owner together with architect Marc Reniers.

As part of the Erasmus Programme he initiated, curated, and has taught a workshop series in seven European countries since 2008.

In his educational projects, such as Tastenderwijs (2004), The Temporary Expert (2004–07), Building Tectonics (2007–14), Crafting the façade (2015-17), Spaan largely focusses on the creation of sensory experiences of architecture through engagement with materials and exploration of form.

A hallmark of Spaan's approach is an active engagement with the design question, taking confluence as a starting point.

Questioning the physical, social, and historical context in an ongoing process towards innovation of the architectural form.