The recommended minimum height for the climbing walls at a bouldering gym is 3 m (10 ft) in order to make a sufficient training facility. This requires a minimum ceiling clearance of 3.5 m (11.5 ft) for the building that will house the facility. Less than 3 m (10 ft) bouldering walls are only recommended for kids bouldering area.
The maximum height of a bouldering wall considered safe is 4.5 m (15 ft) which would require a location with at least 5 m (16.5 ft) clear ceiling height.
How do we calculate
Roughly, add 0.5 m (1.5 ft) on top of the desired bouldering wall height in order to calculate the minimum ceiling height required. There are many other site-specific factors in terms of architecture and engineering that need to be taken into account (i.e. fire safety systems, ventilation etc.) but this gives a general idea about what location should a customer seek for their desired facility.