GLA in CRE is an abbreviation for gross lettable area.
This is the amount of space in a commercial building that can actually be rented by a tenant.
It is normally expressed as square meters or square feet.
In most cases, this includes basements, mezzanines, or upper floors that a tenant can potentially utilize. Typically GLA is measured from the center of a wall or other partition that separates tenants from the lease line in common areas. It also fully takes into account any walls that are not shared with other tenants.