Does GST apply to office rent?

GST would be applicable only if the building owner is registered under GST act, or if he has crossed its limit for registration under GST act...

Are you the owner or tenant?

GST applicability and charging GST in an invoice is the property owner's problem. 

If you are the owner and are subject to GST (based on the overall nature of all your incomes and other qualifying factors) then you need to charge GST on the rent.

And if you are the tenant, and the owner has not applied GST (whether or not they're required to) then it's not your lookout.

If the turnover (including taxable and exempted sales or services )of your firm exceeded basic threshold under GST and renting office is one of the service under your sales or services then you are liable to issue a GST invoice for renting office premises if you are already a registered person under GST. If you are not registered already basic threshold limit for to get registered as a dealer has crossed recently then get registered as dealer and issue GST invoice for office rent along with other taxable turnover.

Above explanation is given based on my current level of knowledge any clarifications or suggestion are accepted.

thank you.