By maximizing the block’s Floor Area Ratio (FAR), the community inhabiting the block expands their capacity in a super lightweight cross-laminated timber overbuild, utilizing existing structures as a platform for new social spaces, workshops, daycare, parkland, and home offices. A system of trombe-wall garden facades grows as the new face of the inward facing housing, making oxygen, and sequestering carbon. Collective self-government, Tenant-in-Common financing, and sweat equity systems coordinate labor, services, and ownership; while a system of trade apprenticeship builds knowledge without bias toward digital or physical work, transferring expertise through generations. While co-operative ownership models are valuable in keeping the city affordable, they only do so much against aging building stock, rising property values, and climate change. Nine Reciprocities leverages the collective interest and skill of neighbors to claim air rights and age in place.