A filler block, also known as a Maruthi block or hollow clay roof block, is a type of block used in roof construction to reduce the amount of concrete and steel needed. It is often made by clay brick and tile manufacturers, particularly in Kerala and Karnataka.

Strength and Durability:
Filler blocks offer strength and durability comparable to regular RCC roofs, with the added benefits of passive solar cooling, reduced roof weight, and different looks when seen from the room below.
Thermal Insulation:
Filler blocks offer excellent thermal insulation properties due to the air gaps present in their design. This makes them an energy-efficient solution for roof construction, particularly in hot and humid climates.
Fire Resistance:
Filler blocks offer fire resistance properties due to their noncombustible nature. The fire-resistance ratings of filler block walls depend on the thickness of the walls and the materials used in their construction.
Low Maintenance:
The low maintenance of filler blocks is due to their design and material properties. They are resistant to corrosion, rot, and decay, which means they do not require frequent repairs or replacements. Additionally, their lightweight nature makes them easy to install and handle, reducing the risk of damage during installation.