Building Materials for a House in Mumbai and Thane: What to Use and Why

For a house, redevelopment or flat in Mumbai or Thane, use a concrete frame designed for severe exposure, walls of AAC block or BIS-marked fly ash brick, and waterproofing for the terrace, toilets, plinth and outer walls chosen at design stage. Over 95% of the rain falls from June to September, and sea air works on the steel all year.

Below are the codes and data behind each choice, with indicative state rates. For what a whole house costs, see our Mumbai and Thane construction cost guide.

What Mumbai's climate and ground ask of a building

Four months of rain

The India Meteorological Department's climatological table for Mumbai Santacruz gives a mean annual rainfall of 2,502.3 mm. July alone brings 919.9 mm over 23.3 rainy days, and June to September together bring 2,390.5 mm, over 95% of the year. Colaba follows the same pattern, with 2,213.4 mm a year.

At Santacruz mean daily temperatures run from a 16.9 °C low in January to a 34.1 °C high in November. BEE's Eco-Niwas Samhita 2018, the energy code for homes, lists Mumbai in the warm-humid climate zone. Water comes first here, heat second.

Basalt, alluvium and reclaimed land

The Central Ground Water Board's Greater Mumbai report says the entire district is underlain by basaltic lava flows of the Deccan Trap, with rhyolite and trachyte, and alluvium along the rivers and the coast. It also records that the city began as seven islands joined by reclamation. Its Thane district report describes Deccan Trap basalt with a weathered layer 1 to 8 m deep, and coastal alluvium up to about 20 m thick in the west.

Guidance: one plot sits on rock a metre down, the next on fill and marine clay. Only a soil investigation can say whether open footings will do or the building needs piles.

Earthquakes and wind

• Earthquakes: Annex E of IS 1893 (Part 1) places both Mumbai and Thane in Seismic Zone III, zone factor 0.16. The 2016 edition is the one in force: BIS released a 2025 edition with a new zone map in November 2025 and withdrew it in March 2026 (ETV Bharat, 11 March 2026).
• Wind: IS 875 (Part 3) lists a basic wind speed of 44 m/s for Bombay in the 1987 edition we opened. Ask your structural engineer to confirm it from the current 2015 edition, for parapets, tanks, solar frames and canopies.

The frame: design the concrete for severe exposure

IS 456:2000, the concrete code, guards against rusting steel through exposure classes, and Mumbai meets the severe class twice over.

• Table 3 calls concrete "exposed to coastal environment" severe. So are surfaces exposed to severe rain or alternate wetting and drying: every outer face in a Mumbai monsoon. Sea water spray is very severe.
• Table 16 sets the nominal cover to reinforcement at 45 mm for severe and 50 mm for very severe (5 mm less at M35 and above), against 20 mm for mild.
• Table 5 sets the minimum for reinforced concrete in severe exposure at M30, with at least 320 kg of cement per cubic metre and a water-cement ratio of 0.45 at most.
• Clause 8.2.8 says slag or pozzolana cement is advantageous along the sea coast.

Guidance: whether corrosion-resistant (CRS) bars, priced in the table below, are worth it is your engineer's call. The cheap habits matter more: correct cover blocks, steel stored covered and off the ground, and proper curing.

Walls: AAC, fly ash brick or burnt brick

Trade press was describing AAC block as a wall material for high-rise residential buildings more than a decade ago (Construction World, 2013, which named a Mumbai residential project and a Mumbai hospital built with it). We found no published survey of AAC's share of the region's walls, so we cannot put a number on its dominance. The reasons it suits towers are in the codes:

By Table 7 of the Eco-Niwas Samhita, AAC weighs a third to under half as much as solid brick, which lightens a tall frame and its foundations, and lets through far less heat. An IIT Bombay study reported by the Free Press Journal (October 2024) found AAC kept naturally ventilated homes more comfortable than stabilised earth block, burnt brick or fly ash block, while noting its lower strength.

The fly ash rule. MoEFCC's ash notification, as amended by S.O. 05(E) of 1 January 2024, requires all building construction projects, including "all private agencies", within 300 km of a coal or lignite power plant to use ash bricks, tiles or other ash-based products, provided they cost no more than the CPWD or state PWD Schedule of Rates price. The Central Electricity Authority's fly ash report for 2021-22 lists coal stations at Trombay, inside Mumbai, and at Dahanu, so Mumbai and Thane are well within that radius. It does not say whether this binds a family's own home, so ask your architect and the local authority; do not treat it as merely optional.

Guidance: lay AAC in its thin-bed jointing mortar and follow the maker's plastering method, or it cracks at joints. For any block or brick, ask for the BIS licence number, the grade and a dated batch test certificate.

Roof and terrace: drainage before anything else

IS 3067:1988, the code for detailing damp-proofing and waterproofing, names rainfall intensity and drainage among the factors that decide a roof treatment. It asks for outlets placed so water cannot collect, drain mouths widened to two and a half times the pipe diameter, and a concrete fillet around pipes through the roof.

Heat still counts: the Eco-Niwas Samhita caps roof U-value at 1.2 W/m²K, and its example slab with 40 mm of PUF insulation reaches 0.47.

Guidance: slope the screed to more outlets than you think you need, add overflow spouts in the parapet, protect any membrane under a screed or tiles, and use a root-resistant layer under planters. Gardens and water features, like those above, need waterproofing designed before landscape.

Waterproofing is a first-order decision

In Mumbai waterproofing is not a finishing item to price at the end. The state's own Schedule of Rates writes ponding tests and stamp-paper guarantees into its items.

• Terrace: brick-bat coba laid to slope with a waterproofing compound, rounded parapet junctions, a drip mould, a ponding test and a 10-year guarantee. Or a five-course bitumen felt treatment to IS 1346 with a four-year guarantee, or an acrylic polymer-modified cement coating with a fibreglass mesh and a seven-year guarantee.
• Toilets and floors: a waterproofed bed under the tiles, sloped to the drain, with a ponding test and a 10-year guarantee. Vitrified tile, Kota or granite all suit, laid on it.
• Plinth: a 50 mm damp-proof course in M20 concrete. For basements, IS 3067 requires external damp-proofing in all new structures.
• Outer walls: sand-faced cement plaster whose base coat carries a waterproofing compound at 1 kg per bag of cement, cured for 14 days. Add drip moulds and chajjas over openings.

Redevelopment and flat renovation

For approvals, see our guides to building permission in Mumbai and building permission and cluster redevelopment in Thane.

Guidance for a society redeveloping: materials are fixed in the developer agreement. Ask for a specification schedule naming the concrete grade, exposure class and cover, the wall block and its BIS standard, and the waterproofing system for the terrace and toilets with its guarantee period.

Guidance for a flat renovation: never cut columns, beams or slabs, and get a structural engineer's sign-off before swapping brick partitions for lighter AAC. A leaking toilet floor damages the flat below, so relay the bed with a ponding test before tiling. For an old leaking toilet, the Schedule of Rates carries injection grouting through the existing tiles.

Local materials: basalt

Deccan basalt was designated a Heritage Stone by the International Union of Geological Sciences in 2022. The listing credits its abundance, workability and durability and names Mumbai's High Court, General Post Office and Crawford Market among buildings made from it. The state Schedule of Rates still prices trap rubble masonry for foundations and plinths. Guidance: on basalt ground it makes a sound, economical plinth under a damp-proof course.

Indicative rates from the Maharashtra Schedule of Rates

Laid, the three wall types sit within about 13% of each other. The real differences are dead load, heat and plastering.

To check current prices: look for a newer edition on the PWD's State Schedule of Rates page, then compare three written quotes showing GST, delivery and BIS licence number.

Mistakes to avoid

• Designing the frame for mild exposure with 20 or 25 mm cover.
• Leaving waterproofing until after the slab, with no system, test or guarantee written down.
• Terraces with one outlet, no overflow and planters straight on the slab.
• Removing or chasing into structural walls, beams or columns during a flat renovation.

FAQ

Which is better for a house in Mumbai, AAC block or red brick?

Both work. AAC is much lighter and keeps out more heat, so it suits towers and upper floors. Bricks are heavier and familiar to every mason. In Mumbai, plaster, drips and waterproofing decide whether any wall stays dry.

What is the AAC block price in Mumbai?

The Maharashtra Schedule of Rates 2022-23 lists a 600 x 200 x 100 mm AAC block at ₹58 and laid AAC masonry at ₹7,340 per cubic metre, excluding GST. These are indicative 2022 state rates; get dated written quotes.

Which waterproofing is best for a Mumbai terrace?

No single system is best. What matters is slope, enough outlets, a protected membrane, a ponding test and a written guarantee.

Choose materials with someone who knows the site. An architect can match the frame, walls and waterproofing to your soil, your distance from the sea and your building. Consult an architect on MOA, or see studios in Mumbai.

Sources

• India Meteorological Department: Mumbai Santacruz climatological table, 1991-2020 (accessed 17 Oct 2026)
• India Meteorological Department: Mumbai Colaba climatological table, 1991-2020 (accessed 17 Oct 2026)
• Bureau of Energy Efficiency: Eco-Niwas Samhita 2018, Part I: Building Envelope, copy on the Asia Pacific Energy Portal (accessed 17 Oct 2026)
• Central Ground Water Board: Ground Water Information, Greater Mumbai District (accessed 17 Oct 2026)
• Central Ground Water Board: Ground Water Information, Thane District (2013) (accessed 17 Oct 2026)
• Bureau of Indian Standards: IS 1893 (Part 1):2002, Criteria for Earthquake Resistant Design of Structures, via Public.Resource.Org (accessed 17 Oct 2026)
• ETV Bharat: A Bold Policy Reversed: The Withdrawal of India's 2025 Seismic Code (accessed 17 Oct 2026)
• Bureau of Indian Standards: IS 875 (Part 3):1987, Wind Loads, via Public.Resource.Org (accessed 17 Oct 2026)
• Bureau of Indian Standards: IS 456:2000, Plain and Reinforced Concrete: Code of Practice, via Public.Resource.Org (accessed 17 Oct 2026)
• Bureau of Indian Standards: IS 2185 (Part 3):1984, Autoclaved Cellular (Aerated) Concrete Blocks, via Public.Resource.Org (accessed 17 Oct 2026)
• Bureau of Indian Standards: IS 12894:2002, Pulverized Fuel Ash-Lime Bricks, via Public.Resource.Org (accessed 17 Oct 2026)
• Bureau of Indian Standards: IS 1077:1992, Common Burnt Clay Building Bricks, via Public.Resource.Org (accessed 17 Oct 2026)
• Bureau of Indian Standards: IS 3067:1988, Code of Practice for General Design Details and Preparatory Work for Damp-Proofing and Water-Proofing of Buildings, via Public.Resource.Org (accessed 17 Oct 2026)
• Construction World: Top of the block (2013) (accessed 17 Oct 2026)
• Free Press Journal: IIT-B Research Develops New Method For Selecting Wall Materials To Enhance Indoor Comfort In Naturally Ventilated Homes (accessed 17 Oct 2026)
• Ministry of Environment, Forest and Climate Change: S.O. 05(E), 1 January 2024, amendment to the ash utilisation notification (accessed 17 Oct 2026)
• Central Electricity Authority: Report on Fly Ash Generation at Coal/Lignite Based Thermal Power Stations and its Utilization, 2021-22, via CPCB (accessed 17 Oct 2026)
• International Union of Geological Sciences: Heritage Stones: Deccan Basalt (accessed 17 Oct 2026)
• Government of Maharashtra, Public Works Department: State Schedule of Rates 2022-2023 (accessed 17 Oct 2026)