GUIDE

CSEB vs red brick, fly ash bricks, AAC and concrete blocks

Most houses around Hyderabad are built with one of four walling materials: red bricks, fly ash bricks, AAC blocks or concrete blocks. Compressed stabilised earth blocks (CSEB) are pressed from soil with a little cement instead. Here’s how CSEB compares with each one, where each does better, and where the numbers come from.

Last checked: 25 October 2026

The five materials

CSEB (compressed stabilised earth blocks): subsoil with around 5% cement and a little water, pressed hard in a machine and cured for about four weeks. Not fired.
Red bricks: clay moulded by hand (country bricks) or extruded and wire-cut by machine, then fired in a kiln.
Fly ash bricks: fly ash from thermal power plants, mixed with lime or cement and sand, pressed and cured. Not fired.
AAC blocks (autoclaved aerated concrete): cement, lime, fine sand or fly ash and an aerating agent that fills the mix with tiny air pockets, cured with steam under pressure. Large, light blocks.
Concrete blocks: cement, sand and crushed stone, moulded solid or hollow and cured.

Side by side

CSEB compared with the walling materials most used around Hyderabad
	CSEB	Red brick	Fly ash brick	AAC block	Concrete block
Fired in a kiln?	No	Yes	No	No (steam-cured)	No
Main raw material	Subsoil, often from your site	Clay, often topsoil from farmland	Fly ash from power plants	Cement, lime, sand or fly ash	Cement, sand, crushed stone
Strength	About 7.5 MPa average, dry (Auroville’s tests)	Graded 3.5 to 35 MPa; country-fired about 3.5 MPa (Auroville)	Graded 3.5 to 30 MPa	Graded 1.5 to 7 MPa, by density	Hollow graded 3.5 to 15 MPa; solid 4 or 5 MPa
Usual finish	Can be left exposed	Plastered; wire-cut bricks are often left exposed	Usually plastered	Plastered	Usually plastered
Where it’s made	On or near your site	Kilns	Factories	Factories	Factories and block yards
Ready to use	After about four weeks of curing	Bought ready	Bought ready	Bought ready	Bought ready
Indian Standard	IS 1725	IS 1077	IS 12894	IS 2185 (Part 3)	IS 2185 (Part 1)

CSEB compared with the walling materials most used around Hyderabad

CSEB

Fired in a kiln?: No
Main raw material: Subsoil, often from your site
Strength: About 7.5 MPa average, dry (Auroville’s tests)
Usual finish: Can be left exposed
Where it’s made: On or near your site
Ready to use: After about four weeks of curing
Indian Standard: IS 1725

Red brick

Fired in a kiln?: Yes
Main raw material: Clay, often topsoil from farmland
Strength: Graded 3.5 to 35 MPa; country-fired about 3.5 MPa (Auroville)
Usual finish: Plastered; wire-cut bricks are often left exposed
Where it’s made: Kilns
Ready to use: Bought ready
Indian Standard: IS 1077

Fly ash brick

Fired in a kiln?: No
Main raw material: Fly ash from power plants
Strength: Graded 3.5 to 30 MPa
Usual finish: Usually plastered
Where it’s made: Factories
Ready to use: Bought ready
Indian Standard: IS 12894

AAC block

Fired in a kiln?: No (steam-cured)
Main raw material: Cement, lime, sand or fly ash
Strength: Graded 1.5 to 7 MPa, by density
Usual finish: Plastered
Where it’s made: Factories
Ready to use: Bought ready
Indian Standard: IS 2185 (Part 3)

Concrete block

Fired in a kiln?: No
Main raw material: Cement, sand, crushed stone
Strength: Hollow graded 3.5 to 15 MPa; solid 4 or 5 MPa
Usual finish: Usually plastered
Where it’s made: Factories and block yards
Ready to use: Bought ready
Indian Standard: IS 2185 (Part 1)

How to read the strength row: the Indian Standards set a minimum strength for each grade a maker can sell, so the ranges show the grades, not what any one product achieves. Auroville’s CSEB number is a measured dry average from Auroville conditions, while the standards test by their own methods, some on soaked units. Compare the grade of what you actually buy. Hyderabad numbers for our blocks will come from our own tests once our first batches finish curing.

CSEB vs red brick

Red brick is still the usual choice for independent houses around Hyderabad. Country bricks are moulded from clay, often topsoil from farmland, and fired for days; the firing is where most of a brick’s energy and carbon goes. The Auroville Earth Institute measured well-made CSEB at about 7.5 MPa average dry strength, against about 3.5 MPa for country-fired bricks, with about 12 times less carbon.

Machine-made wire-cut bricks are a different product: more regular, and made in higher strength grades. So don’t assume CSEB is stronger than every brick; compare the grade.

On cost, the Auroville Earth Institute found a finished CSEB wall cost 20–25% less than a country-fired brick wall in Auroville, mostly because it needed no plaster and less mortar, not because the block itself was cheaper.

Red brick may suit you better if:

Your design has a concrete frame and the walls are only infill. Earth blocks earn their keep in load-bearing walls.
You want a fully plastered and painted finish anyway, which takes away one of CSEB’s savings.
You need to start the walls this week. CSEB needs about four weeks of curing, so block making has to start early.

Source: Auroville Earth Institute: Compressed Stabilised Earth Block

CSEB vs fly ash bricks

Fly ash bricks are everywhere around Hyderabad. They put a power-plant waste to use, they aren’t fired, they come in a regular size, and they’re easy to buy ready-made.

The differences: fly ash bricks are made in factories and trucked to you, and are usually plastered. CSEB can often be made from the soil on your own site, in larger blocks, and left exposed.

Fly ash bricks may suit you better if:

You want ready-made bricks delivered this week, with no block making on site.
You plan to plaster and paint every wall.
Your soil doesn’t suit blocks and there’s no CSEB supply nearby.

Source: IS 12894:2002, Pulverized fuel ash-lime bricks: strength classes 3.5 to 30 N/mm² (Table 1)

CSEB vs AAC blocks

AAC blocks are large and light: their Indian Standard covers blocks up to 1,000 kg per cubic metre. The tiny air pockets slow heat passing through the wall, and the standard caps their thermal conductivity at 0.21 to 0.42 W/m·K, depending on density. They’re most often used to fill in the walls of concrete-framed buildings, such as apartments.

Earth blocks work differently. A thick earth wall is heavy, so it takes in the day’s heat slowly and gives it out at night. We use it as the load-bearing wall itself, without a concrete frame, for homes up to G+2.

Which house stays cooler depends as much on the roof, shading, windows and cross-ventilation as on the wall material.

AAC may suit you better if:

You’re building with a concrete frame and want light infill walls.
You want walls that insulate, and you’ll plaster them anyway.
You’re building taller than G+2. We build earth-block homes up to G+2 only.

Source: IS 2185 (Part 3):1984, Autoclaved cellular (aerated) concrete blocks: density up to 1,000 kg/m³, strength 1.5 to 7 N/mm², thermal conductivity 0.21 to 0.42 W/m·K (Table 1)

CSEB vs concrete blocks

Concrete blocks are quick to lay and easy to buy. Solid blocks are dense (their standard asks for at least 1,800 kg per cubic metre), and hollow ones are made in a wide range of grades, which is why they’re common for compound walls and budget builds. They’re usually plastered.

Concrete blocks may suit you better if:

You need a quick compound wall or outbuilding and don’t mind a plastered finish.
You need blocks right away and can’t wait about four weeks for CSEB to cure.
Your engineer has specified a block grade that CSEB can’t meet.

Source: IS 2185 (Part 1):2005, Hollow and solid concrete blocks: grades 3.5 to 15 N/mm², solid blocks at least 1,800 kg/m³ (Table 2)

What about cost?

We don’t publish block or wall prices for Hyderabad yet. Your cost depends on whether blocks can be made from your own soil, how far materials travel, and whether you leave the walls exposed. After a plot visit and a soil test, we give you a quote you can compare with others.

When CSEB makes more sense

You’re building a load-bearing home of up to G+2.
You like the look of bare, natural walls and want to skip plaster.
You care about cooler rooms and a lower-carbon house.
Your soil tests suitable, so the blocks can be made on or near your site.

How we build CSEB houses →Earth blocks and soil tests from CJ EcoTech →

Quick answers

Is CSEB stronger than red brick?

Than country-fired red brick, yes: Auroville’s tests found well-made CSEB averages about 7.5 MPa dry strength, against about 3.5 MPa for country-fired bricks. Machine-made wire-cut bricks come in higher grades, so compare the grade. These are Auroville’s numbers; Hyderabad numbers will come from our own tests.

Is CSEB better than AAC blocks?

They do different jobs. AAC is light and insulates, and is mostly used to fill in the walls of concrete-framed buildings. CSEB is heavy, stores heat, and we use it as the load-bearing wall of homes up to G+2. For a concrete-framed building, AAC may suit you better.

Are fly ash bricks eco-friendly?

They put fly ash from power plants to use and aren’t fired, which counts in their favour. CSEB’s advantages are different: it can often be made from the soil on your own site, so less is trucked in, and the walls can be left unplastered.

Will CSEB walls get damaged in the rain?

The cement in the mix stabilises the blocks. Like any wall, they last longest with a raised plinth, roof overhangs and good drainage.

Can I use CSEB for a compound wall?

Yes. Some people start with a compound wall or a garden room before building a whole house.

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Tell us where your plot is. We’ll tell you what a soil test involves and what it would take to build with earth blocks.