Guide

What to ask a contractor before you sign

Seven questions, and the two answers that tell you more than the rest put together.

How do you compare contractor quotes when the numbers make no sense?

You show your concept drawing to three contractors. You get three completely different rates. One quotes ₹1,700 per square foot. Another quotes ₹2,200 per square foot. The third quotes ₹2,500 per square foot. None of them explain what their number includes or excludes.

If you choose the lowest number blindly, you absorb the difference later. Contractors make up for low bids through variation bills. They bill extra for chasing conduits into brickwork. They bill extra for casting the plinth higher off the ground. They bill extra for external drainage lines.

By the time the roof slab is cast, your costs match or exceed the highest initial bid. You cannot easily fire a contractor in the middle of casting a slab. You protect your budget before signing an agreement by asking specific technical questions.

The cost baseline and the engineering boundaries

Construction cost anchors for 2026 across India sit in three broad bands. A basic finish runs ₹1,600 to ₹2,000 per square foot. A standard finish runs ₹2,000 to ₹2,800 per square foot. A premium finish runs ₹2,800 to ₹4,500 and above per square foot. These are planning figures and broad estimates, not formal quotations. A local contractor can price a build accurately only with engineering drawings in hand. For example, on a 995 square foot house we drew, building at ₹1,700 per square foot costs about ₹16.9 lakh.

A contractor does not design the structure. Under the National Building Code, structural elements belong strictly to the structural engineer. This includes the roof, lintels, monitor openings, stepped walls, and wardrobe niches. If masonry is load-bearing, seismic banding must follow IS 4326 and IS 13828. Our practice sets the plinth at +600 mm above finished ground level, with a planted swale falling away on all sides.

Every square-foot quotation depends on how the contractor measures the area. Some bill on carpet area. Some bill on built-up area. Others bill on slab projection area, charging full rate for balconies and overhangs.

How the questions are applied

Use these seven questions to evaluate contractor responses. The two answers that matter most are the area definition and the casting of embedded services.

The area definition decides whether two quotes are genuinely comparable. A quote of ₹1,700 per square foot measured across the slab edge often costs more than a quote of ₹2,000 per square foot measured strictly across enclosed rooms. Ask the contractor to mark their measurement boundary on your floor plan. If external steps, balconies, and open utility areas are billed at the full rate, recalculate the true rate across your enclosed space before comparing.

The second critical answer is how services are installed. Our practice mandates that conduit, back-boxes, soil stacks, extract ducts, and curtain pelmets must be built in directly as the walls rise. You must insist on this single item in writing. An earth wall or lime wall cannot be chased afterwards without damaging it. Even in brick walls, cutting vertical and horizontal channels after the wall is built weakens the masonry bonds. It also leads to plaster cracks that appear within two years.

For sanitation, check the separation between the septic tank and the borewell. The Tamil Nadu Combined Development and Building Rules 2019 and IS 2470 require at least 18 m of clear separation between a borewell and a septic tank or dispersion trench. If a contractor offers to place the septic tank right beside the house without measuring the well distance, they violate code. On a 40 × 60 ft plot, the diagonal is about 22 m, meaning the two can only sit in opposite corners. On a 30 × 40 ft plot, an 18 m separation does not fit at all.

For clear space, check door swings and circulation. The National Building Code Part 3 requires a minimum corridor clear width of 914 mm inside the partition faces. Our practice also warns whenever a door leaf clears an internal fixture by under 50 mm. A contractor must verify wall thickness early. If you plan for a 110 mm partition, the contractor cannot substitute a thicker block without stealing your corridor width.

The mistake this prevents

Asking these questions prevents expensive rework and hidden charges.

Consider a 995 square foot house. If a contractor quotes ₹1,700 per square foot on a slab-area basis, you expect to spend ₹16.9 lakh. If that quote omits the +600 mm plinth height, the site filling costs you extra. If it omits built-in conduit channels, cutting chases across completed rooms adds thousands of rupees in labour and patch plastering.

In our own project checks, failing to monitor physical partitions led to a corridor finishing at 804 mm clear instead of the 914 mm required by the National Building Code. A 110 mm partition had been built into the clear zone. Correcting that mistake on site means demolishing and rebuilding the entire partition wall. Asking these questions upfront holds the contractor to the clear dimensions on the paper.

What this means for your plan

Check every quotation against your actual floor dimensions rather than accepting an unverified flat rate. Ask your contractor to confirm the +600 mm plinth height, the 18 m sanitation setback, and the built-in conduit sequence in writing. The planning tool checks clearances, door swings, and code separations automatically when it draws your plan. You can hand your dimensioned sketch directly to a licensed structural engineer and an experienced builder with the rules already set.

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