AAC Blocks vs Red Bricks: Cost, Strength and Which to Use
AAC blocks vs red bricks: AAC (autoclaved aerated concrete) blocks are large, light blocks, roughly a third of the weight of red brick for the same volume. They insulate heat better and build walls faster with less mortar. Red clay bricks are heavier and stronger per unit, absorb knocks and fixings better, and suit load-bearing walls and wet, below-plinth areas. In an RCC-framed house, AAC is a good choice for walls above plinth; red brick is still preferred for load-bearing houses, compound walls and wet areas.
Most new RCC houses in Indian cities now ask the same question at the walling stage: “lal eent ya AAC block?” The answer affects the weight on the structure, how hot the rooms get in summer, how fast the walls go up and how the plaster behaves. This guide compares the two in plain terms, with the typical values engineers use, and explains where each one works best.
Last updated: 24 October 2026
AAC blocks vs red bricks: quick comparison
| Factor | AAC block | Red clay brick |
|---|---|---|
| What it is | Cement, lime, fly ash or sand, water and aluminium powder, foamed and cured in an autoclave | Clay moulded and fired in a kiln |
| Indian standard | IS 2185 (Part 3) | IS 1077 (common burnt clay bricks) |
| Typical size | 600 × 200 mm face; 100–300 mm thick | About 230 × 110 × 75 mm (traditional) or 190 × 90 × 90 mm (modular) |
| Typical density | About 550–650 kg/m³ | About 1,600–1,900 kg/m³ |
| Compressive strength | Typically about 3–4 N/mm² | Depends on class; common site bricks often 3.5–10 N/mm² |
| Heat insulation | Much better | Lower; walls hold heat and release it at night |
| Joint | Thin-bed adhesive (about 3 mm) or thin mortar | 10–12 mm cement mortar |
| Speed of building | Faster: one block replaces many bricks | Slower |
| Load on the structure | Low; can reduce beam, column and footing sizes if designed for it | High |
| Load-bearing walls | Generally used as infill in RCC frames | Widely used for load-bearing walls in low-rise houses |
| Moisture | Porous; must be protected and plastered correctly | More tolerant; used below plinth and in wet areas |
| Fixing heavy items | Needs anchors made for AAC | Normal plugs and screws work well |
| Sound insulation | Fair | Better, because of higher mass |
What are AAC blocks?
AAC stands for autoclaved aerated concrete. A slurry of cement, lime, fine sand or fly ash and water is mixed with a small amount of aluminium powder, which reacts and releases gas, so the mix rises like a cake. It is cut into blocks and cured under steam pressure in an autoclave. Most of the block’s volume is tiny closed air pockets, which is why it is light and a good insulator. Many Indian plants use fly ash, an industrial by-product. For a related fly ash product, see fly ash bricks.
What are red bricks?
Red bricks, or burnt clay bricks, are made by moulding clay and firing it in a kiln, which gives the red colour. They have been the standard walling unit in India for generations. Quality varies widely between kilns: a good brick is well burnt, has sharp edges, gives a clear ringing sound when two are struck together, and does not absorb too much water. IS 1077 classifies them by compressive strength.
Where AAC blocks work best
- Infill walls in RCC-framed houses and apartments, above the plinth, where the frame carries the load.
- Upper floors and extensions, where a lighter wall reduces the load on existing beams and columns (with an engineer’s check).
- Hot climates, especially west- and south-facing external walls and top-floor rooms, where better insulation means cooler rooms and lower AC use.
- Projects where speed matters, because large blocks and thin joints build walls quickly.
Where red bricks work best
- Load-bearing houses without an RCC frame, where the walls carry the roof.
- Below plinth and foundations, and the lower courses of walls in bathrooms and wet areas.
- Compound walls exposed to rain on both faces; see compound wall designs.
- Walls carrying heavy fixtures, such as kitchen cabinets, geysers and wall-hung WCs, unless AAC-rated anchors are used.
- Exposed brick finishes and places where a traditional look is wanted.
Building with AAC: what to get right
- Use the right joint. Thin-bed block adhesive gives thin, strong joints. If cement mortar is used, keep it thin and do not soak the blocks; dampen the surface lightly instead. Red bricks, by contrast, should be soaked before laying.
- Start on a damp-proof base. Lay the first course on a level bed above the DPC; many builders use a course of brick or concrete at the bottom of walls in bathrooms and kitchens.
- Treat the junctions. AAC and RCC move differently, so cracks often appear where block walls meet columns and beams. Fixing chicken mesh or fibre mesh across these junctions before plastering, and leaving a small gap under the beam filled with a flexible filler, reduces cracking.
- Plaster correctly. AAC is porous and absorbs water from plaster. Use a bonding coat or plaster made for AAC, keep plaster thin and even, and cure it properly.
- Plan fixings and chases. Cut chases for conduits with a groove cutter, not a hammer, and use anchors designed for AAC for heavy items.
Cost: which is cheaper?
Comparing the price of one block with one brick is misleading. A fair comparison is the finished cost per square metre of wall, including mortar or adhesive, labour, plaster and wastage. AAC usually uses much less mortar and goes up faster, while brick may need thicker plaster to even out the surface. There can also be savings in the structure: a lighter wall reduces the load on beams, columns and footings, but only if the structural engineer designs for AAC from the start. Prices vary by city and supplier, so get quotes for both and compare them per square metre of finished wall. To estimate the number of bricks for a wall, use the brick quantity calculator; for the overall budget, use the construction cost calculator.
Hindi terms used on site
Red brick is लाल ईंट (laal eent) and the bricklaying work is चिनाई (chinai). AAC blocks are usually just called “AAC block” on site. Mortar is मसाला (masala) and plaster is प्लास्टर (plaster).
FAQ
Which is better for a house, AAC blocks or red bricks?
For walls above plinth in an RCC-framed house, AAC is often the better choice: lighter, faster to build and cooler in summer. For load-bearing houses, foundations, compound walls and wet areas, red brick is usually the safer choice.
Are AAC blocks strong enough?
AAC is strong enough for infill walls in framed buildings. It has lower compressive strength than good clay brick, so it is not normally used for load-bearing walls unless specifically designed.
Do AAC walls crack?
Cracks mostly appear at junctions with RCC columns and beams, or from poor plastering. Mesh at junctions, correct joints and proper curing of the plaster prevent most of them.
Can AAC blocks be used in bathrooms?
Yes, above a damp-proof base and with proper waterproofing and tiling. Many builders use brick or concrete for the lowest courses in wet areas.
Do AAC blocks keep the house cooler?
Yes. Their much lower thermal conductivity reduces heat passing through external walls, which helps most on sun-facing walls and top floors.
Related guides: Fly ash bricks · Parts of a building · OPC vs PPC cement · Brick quantity calculator · All construction guides
Disclaimer: Educational only. Wall material, thickness and load-bearing use must follow your architect’s and structural engineer’s design and the relevant IS standards. Typical values vary by manufacturer. Disclaimer
Tanmay Arora, is an Architect with an experience of 13+ years. He is a Management Grad with a post Graduate Diploma in Building Construction and Materials. Tanmay has worked with renowned firms. He has graduated in Bachelor of Architecture. His deep interest in Architecture and Civil Engineering and his experience has made him one of the best architects a client can think of.
