The size of concrete blocks in Brazil follows a standardized system, but there's a crucial distinction to understand: the nominal dimension (Dimensional Nominal) versus the actual dimension (Dimensional Real).
This is because the specified size includes the block plus the intended mortar joint (usually 10mm).
Here are the most common nominal sizes (the finished size of the wall including mortar):
Nominal Size: 14 x 19 x 39 cm
This is the "language" used on architectural plans and when ordering.
It means the wall, once built, will have a thickness of 14cm.
Actual Size (Approximate): ~14 x 19 x 39 cm
Wait, the same? For this specific block, often yes. The 14cm thickness is the actual structural width. The modularity is maintained in the length and height. The actual length is typically ~39 cm to allow for a 1 cm vertical mortar joint, making the nominal length 40 cm.
Let's clarify with a more modular example:
Nominal Size: 9 x 19 x 39 cm
Interpretation: A 9cm thick wall after laying.
Actual Size: ~9 x 19 x 29 cm
Why 29cm? Because the actual length of 29cm + 1cm of mortar = 30cm nominal length. This 30cm module is also very common.
These are used to create reinforced concrete beams (cintas) on top of walls.
Nominal Size: Matches the wall thickness (e.g., 14 x 19 x 39 cm).
Actual Size: The same as a standard block, but with a "U" shaped channel to hold rebar and concrete.
Used to complete courses, especially at corners and ends of walls.
Nominal Size: Half the length of a standard block (e.g., 14 x 19 x 19 cm).
These are non-structural, used for fences, partitions, and enclosures. They are thinner and lighter.
Common Nominal Sizes: 9 x 19 x 39 cm, 9 x 19 x 29 cm.
