What an ecological brick is
It is a modular soil-cement block: a mix of soil, cement and water compacted under high pressure in a hydraulic press and cured without firing. In market practice, cement makes up around 8% to 10% of the mix, and the soil — sandy, with a controlled clay fraction — accounts for the rest.
What turned this into a building system, and not just an alternative brick, were two design details: the vertical holes, through which services and reinforcement run, and the tongue-and-groove interlock, which aligns the piece by itself and does away with the mortar joint.
It is a standardised material: NBR 8491 and 8492 cover the brick, NBR 10833 manufacturing with a hydraulic press, NBR 10834 and 10836 the hollow block. There is a standard, there is testing and there are acceptance criteria.
The ball test
Squeeze a handful of the mix in your hand. It should form a firm ball that does not crumble and does not leave mud on your fingers. Dropped from chest height, the ball must break apart when it hits the ground.
Crumbled before that? Not enough water. Soggy and sticky? Too much. The wrong moisture ruins the pressing — and no later correction fixes it.
The 12 stages of the build
The sequence below is the same as a conventional build — what changes is how each stage is carried out.
Laying: mortar, adhesive, level and plumb
Mortar only on the first course
It levels the base and corrects the foundation. It is the only course where mortar has a job — on the others it would be waste and would spoil the precision of the interlock.
Adhesive from the second course on
A thin bead of polymer mortar or tile adhesive on the brick’s ribs. It goes a long way, makes little mess and lets you adjust the piece before it sets.
Level and plumb on every course
The interlock aligns horizontally, but the plumb is the bricklayer’s responsibility. Straightedge and plumb on every course, no exceptions.
Bonding at the corners
Corners alternate the piece on every course, as in ordinary masonry. That is what locks the assembly together.
What you can do with the wall
What everyone asks before starting
Is the ecological brick strong?
NBR 8491 requires a minimum average strength of 2.0 MPa at 7 days. With selected soil, the right mix, a high-pressure hydraulic press and proper curing, it is common to go well beyond that floor. Whoever controls the process controls the strength.
Can you build two storeys?
Yes. Two-storey builds are done routinely, with grouted columns and a ring beam sized by structural design.
Do I need to render it?
No. Render is optional. The wall comes out aligned enough to take just paint or varnish — and that is where much of the saving comes from.
Is there a technical standard?
Yes: NBR 8491, 8492, 10833, 10834 and 10836. This is not an informal material — there is a standard, testing and acceptance criteria.
Does it take on moisture?
The brick absorbs water like any ceramic material. That is why waterproofing the foundation and using a water repellent on external faces are not optional.
Will any soil do?
No. The ideal soil is sandy, with a controlled fraction of clay and silt. Very clayey soil swells and shrinks; pure sand gives no cohesion. When the local soil will not do, the mix is corrected.
How long does the brick cure before use?
It can be used on site from 7 days, with strength continuing to grow over the following weeks. Moist curing in the first days is what guarantees the result.
Do I need specialised labour?
You do not need a specialised crew, but you do need a trained one. The method is simpler than conventional masonry — what changes is the first few days, until the bricklayer picks up the rhythm of the interlock.
Can it take cabinets, a TV and air conditioning on the wall?
It can. Suspended loads are fixed with suitable anchors; at higher-load points the hole can be grouted.
Can I set up a manufacturing business?
Yes — it is the path many of our clients take. Producing your own brick changes the economics of the build entirely, and leaves spare capacity to sell in your region.