In a fast selling pocket of south Chennai, a buyer we spoke to booked a smart looking flat on the fourth floor of a new block in 2024. The builder waved a permit from the local panchayat and called it approved. Eighteen months later the residents received a notice: the building was a Special Building inside the Chennai Metropolitan Area, it needed planning permission from CMDA, and it never had one. The panchayat permit was the wrong document from the wrong authority. That single mismatch, which a buyer could have caught in an afternoon, put every flat in the block at risk.

The short answer. Before buying any flat or plot in Chennai, confirm the building or layout has a valid sanctioned plan from the correct authority and verify it on the official Tamil Nadu portal at onlineppa.tn.gov.in. Inside the Chennai Metropolitan Area, CMDA grants planning permission for Special Buildings of G+4 and above or over 15 metres, while ordinary buildings up to G+3 are cleared by the local body. The trade off buyers ignore at their peril: an unapproved or deviated building may be cheaper, but it carries the risk of demolition notices, refused utilities and rejected home loans.

What does a CMDA or DTCP approved plan actually mean?

An approved plan means the government has sanctioned exactly what can be built on that land, and the structure in front of you matches it. Approval is granted under the Tamil Nadu Town and Country Planning Act, 1971 and the Tamil Nadu Combined Development and Building Rules, 2019, which set out how much can be built, the setbacks to leave, and the permitted use. A sanctioned plan is not a rubber stamp; it is the legal boundary of what the property is allowed to be.

For a buyer, the approved plan is the reference document against which everything else is checked. It tells you the number of floors, the built up area, and the layout the authority signed off. If the building on the ground has an extra floor, a covered setback, or a converted terrace that the plan does not show, you are looking at a deviation, and deviations are violations with real consequences. Reading the sanctioned plan is how you separate a compliant home from a future legal headache.

Who approves what in Chennai: CMDA, DTCP or the local body?

The right authority depends on where the property sits and how big the building is. Inside the Chennai Metropolitan Area, CMDA grants planning permission for Special Buildings, defined as G+4 and above or a height above 15 metres, and for multi storeyed buildings. Ordinary buildings up to G+3 within the same area are handled by the local body, which may be the Greater Chennai Corporation, a municipality, a town panchayat or a village panchayat, under CMDA's framework.

Outside the Chennai Metropolitan Area but within Tamil Nadu, the Directorate of Town and Country Planning, DTCP, together with the local planning authority, oversees approvals, with the local body issuing the building permit. The practical lesson for a buyer is simple: match the document to the building. A local panchayat permit produced for a G+4 Special Building inside CMDA limits is a red flag, because that building needed CMDA planning permission, not a local permit.

How do you verify a sanctioned plan before buying?

You verify a sanctioned plan on the official Tamil Nadu single window portal, onlineppa.tn.gov.in, also known as TNOBPAS, which handles applications across CMDA and all local bodies. Ask the seller for the planning permission or building permit number and the digitally signed sanctioned plan, then check the details on the portal rather than trusting a printout. A genuine approval carries a number you can trace and a plan that is digitally signed by the authority.

According to a Tamil Nadu building plan approval guide, the same portal is the designated system for filing and verifying approvals statewide. Once you have the plan, walk the property with it in hand and compare floor by floor. Count the storeys, look at the setbacks, and note anything built that the plan does not show. If the seller cannot produce a digitally signed sanctioned plan at all, treat that as your answer and slow down.

What are the risks of buying an unapproved or deviated building?

The risks are financial, legal and practical, and they land on the buyer, not the seller who created them. A deviation from the sanctioned plan can trigger stop work orders and demolition notices from the authority. Utility boards can refuse or delay permanent water and electricity connections to an unauthorised structure. Banks routinely reject home loan applications where the approval is missing or the building does not match the plan, which also shrinks your pool of future buyers when you try to resell.

None of these consequences care that you bought in good faith. Once you register the property, the exposure is yours. That is why the cost saving on an unapproved building is usually a mirage; the discount is the market pricing in a risk that can cost you far more than you saved. A compliant building with a clean sanctioned plan is worth paying for precisely because it removes that entire category of danger. Buyers who treat the sanctioned plan as a must have document, rather than a nice to have, almost never end up on the wrong side of one of these notices.

CMDA, DTCP and local body permits: how do they compare?

Buyers often blur these authorities together, but they cover different areas and building sizes. This table shows who to expect on the paperwork for a given property.

The takeaway is not to memorise the categories but to match the document to the property in front of you. When the authority on the paperwork fits the building's size and location, the approval is plausible. When it does not, you have found the thing worth investigating before you pay.

What should a Chennai buyer check before paying?

Run these checks before any token advance, because verification is far cheaper now than a legal fight later.

1. Ask for the planning permission or building permit number and the digitally signed sanctioned plan in writing.
2. Confirm the approving authority matches the building's size and location, CMDA, DTCP or local body.
3. Verify the number and plan on the official portal at onlineppa.tn.gov.in, not from a printout alone.
4. Walk the property with the plan and compare floors, setbacks and built up area against the ground reality.
5. Check that the approval is still valid and has not lapsed for the construction stage in question.
6. Cross check the patta and title so the approved plan sits on land the seller genuinely owns.
7. Get a lawyer to review the approvals and title together before you commit any meaningful money.

For the land record side of that checklist, our guide on verifying patta and chitta in Tamil Nadu shows how to confirm ownership, and the numbers you will pay at registration are laid out in our Tamil Nadu stamp duty and registration guide.

How long is an approval valid, and what if the building deviates?

A planning approval in Tamil Nadu is typically valid for three years from issuance, so an old sanction on a long delayed project may need to be current for the stage being built. Ask when the approval was granted and whether it still covers the ongoing or completed construction. An expired approval is not the same as no approval, but it is a gap you want explained before you buy, not after.

If the building deviates from the sanctioned plan, the deviation is the buyer's problem the moment the property is registered in your name. Some deviations can be regularised through official schemes when the government opens them, but that is uncertain, time bound and often costly, and it is never a reason to assume a violation will simply be forgiven. The safer path is to buy a building that already matches its approved plan, and to walk away from one that does not until the seller fixes it.

Frequently asked questions

How do I check if a Chennai building has a valid approved plan?

Ask the seller for the planning permission or building permit number and the digitally signed sanctioned plan, then verify it on the official Tamil Nadu portal at onlineppa.tn.gov.in. Confirm the approving authority, CMDA, DTCP or the local body, matches the building's size and location, and compare the plan against the actual structure.

What is the difference between CMDA and DTCP approval?

CMDA grants approvals inside the Chennai Metropolitan Area, including planning permission for Special Buildings of G+4 and above. DTCP, with the local planning authority, handles approvals in areas outside the Chennai Metropolitan Area but within Tamil Nadu. Both operate under the Tamil Nadu Town and Country Planning Act, 1971.

What happens if I buy a flat that deviates from the sanctioned plan?

Once the property is registered, the deviation becomes your risk. It can attract stop work or demolition notices, refused utility connections and home loan rejection, and it complicates resale. Some violations may be regularised when the government opens a scheme, but that is uncertain and costly, so verifying compliance before buying is far safer.

Is a local panchayat permit enough for a tall building in Chennai?

Not if the building is a Special Building inside the Chennai Metropolitan Area. Such buildings, generally G+4 and above or over 15 metres, need planning permission from CMDA, not just a local body permit. A panchayat permit produced for a tall block inside CMDA limits is a warning sign worth investigating before you pay.

Last updated 14 July 2026. PropNewz Team.