The "building" tag is used for the building outline only, it cannot include the whole piece of land.

You can read more about how to tag buildings on the wiki:
https://wiki.openstreetmap.org/wiki/Key:building

Often in housing estates we just map the land with a single area for all neighbouring houses excluding roads, parks, shops, etc. Then map the houses, driveways, pools, etc as individual features. This way it creates a lot less work rather than mapping individual housing lots which don't really achieve anything.