Are builders allowed to charge on super built-up area under RERA? Chennai homebuyer confused about multiple charges

Hi everyone, I’m in the process of buying a new under-construction apartment in Chennai and I’m getting confused (and frustrated) by how builders structure charges.

Here’s what I’m seeing across multiple builders:

Base price is informally quoted per sq ft on super built-up area

Agreement for Sale mentions carpet area (to comply with RERA)

On top of the base price, builders are charging:

clubhouse charges

service works / infrastructure charges

corpus fund

2 years maintenance upfront

Many of these are calculated per sq ft of super built-up area, not carpet area

My questions:

Under RERA, is the builder allowed to charge anything based on super built-up area, or should everything be carpet-area based?

Is it legal to calculate maintenance / clubhouse / service charges per sq ft of super built-up?

What is the common practice vs what is legally correct?

Have any buyers successfully challenged or negotiated these charges?

Is this just a “standard industry practice” that buyers have to accept?

Would really appreciate inputs from:

recent homebuyers

anyone who has filed a RERA complaint or negotiated successfully

Thanks!