I’d like to point out that a Professional Engineer’s standard of care typically includes a site visit to assess field conditions and get an overall understanding of the structure. This can obviously not be accomplished through the internet. The information provided here is meant for planning purposes only (general sizing and budgeting) and is based on the information provided by you. All loading cases considered are for vertical loads only, no lateral analysis has been completed. The information should be verified by a professional engineer who can visit the site to ensure that potentially important information has not been overlooked or omitted.
Making some assumptions, I would say you are looking at a cost of about $75 to $90 per square foot to convert a rooftop are to an open air gym area. Some uf my assumptions are:
1. Beefing up existing roof system to take the increased Live Load and Dead Load
2. Beefing up support columns, walls and footings below to carry these loads.
3. Providing perimeter walls/fencing to enclose the roof area.
4. Running electrical and plumbing/drainage as needed to specific areas
5. All new floor for gym floor surface.
Hope this helps.
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