The document discusses filler slab roofing, which uses lightweight filler materials in place of concrete in the tension zone of reinforced concrete slabs. This reduces costs by 25-30% compared to standard concrete roofing. Common filler materials include tiles, bricks, shells, and bottles. The filler depth should not exceed the neutral axis depth, typically 60mm for a 125mm thick slab. Reinforcing grids are installed and concrete is poured on top, with filler materials centered in the grid spaces. Filler slabs provide cost savings along with benefits like improved insulation and reduced foundation loads.

1. ROOFING WITH FILLER SLAB

2. RC Filler Slab
The slab filled with lighter filler
materials is known as the filler slab.
LIGHTWEIGHT, INEXPENSIVE MATERIALS such
as lowgrade Mangalore tiles, bricks, coconut
shells, glass bottles, etc. are used as filler
materials in filler slabs to replace the
redundant concrete in tension zones.
Filler slabs are one such cost effective roofing system

3. Concrete is very good in compression while
it is weak in tension. Hence the steel
reinforcement is placed in the tension zone.
The concrete in this portion is only for
holding together the steel reinforcement
and has no structural purpose.
THE NEUTRAL AXIS
In a simply supported RCC slab
The upper part of the slab is subjected to compressive forces
The lower part of the slab experience Tensile forces

4. •Reduces the cost of the slab by around 25-30%
•Creates interesting designs and patterns on the ceiling
•Helps in better thermal insulation of the slab due to
the air pockets present.
•Reduces the load on the foundation

6. The grids of steel reinforcement rods (6mm or 8mm dia.), and
concreting is done over them. The concrete mix used is 1:2:4.
The grid size depends upon the design, span, and the material used.
For Mangalore tiles (size 23cm by 40cm), the grid size is 33cm by50cm.
The filler slab can be designed like a conventional RCC slab as per IS
456-2000 design guidelines,
The thickness of filler material should not exceed the depth of the
neutral axis. Generally speaking, for a slab thickness of 125mm, the
filler material depth should not exceed 60mm.

7. FILLERS
RE-BARS
SERVICE LINES

8. This 'un-productive' concrete can be replaced
by a 'Filler' material which will reduce the
weight of the slab and also reduce the cost by
reducing the amount of concrete used.
This technique saves energy-consuming concrete. Roofs and intermediate floors account for
20-25% of the total cost of the house. This roofing costs 30-35% less than conventionally used
concrete roofing. Thus a considerable amount is saved in terms of materials, energy, and cost.

9. The filler material to be used must be waste materials which
are available locally and lighter than concrete. Filler materials
water absorption should be checked for as it will soak the
hydration water from concrete.
1. The shuttering for slab is erected as for a conventional
RCC slab.
2. 3. A minimum bottom cover of 15 mm is kept after
erecting the shuttering which forms a grid and filler
material can be placed centrally in each space of the grid.
No filler material is provided in bands of concrete along
the edge of the slab. The width of these concrete bands is
normally minimum 300 mm. The reinforcement spacing in
these bands is smaller than spacing around the filler
materials.
3. After all the filler materials have been placed any
concealed electrical work etc., should be placed in the
spaces between the filler material and then concrete is
placed between the filler materials and top of it to
achieve slab thickness.
4. Concrete vibrators must be avoided in bottom portion of
slab as they may disturb the placement of the filler
materials. Manual tamping is advised. Reinforcement
layout for a filler slab using compressed earth blocks as
filler material of size 230mm x 190mm x 50mm.

10. 1)Filler slab roofing(Tiles)
Filler slabs placed on the centering structure
Bar bending work on top of the filler slab Concrete being pored on
top of the filler slab

11. Pots which were used as filler material
Pots being filled with clay before being
placed on the centering structure Concrete being pored on top of pot
Bar bending work on top of the pots
2)Filler slab roofing(Pots)

12. Construction of a slab with terracota pots
Nandanam Kindergarten
Auroville, India

13. WALL HOUSE , AUROVILLE,
Anupama Kundoo- VERNACULAR ARCHITECTURE
Anupama used terracotta pots as
fillers to increase the effective depth
of concrete.
while minimizing the volume of
concrete and steel in the slabs that
did require to be insulated.
One of her aims was to demonstrate
that structural materials can also be
used as finishing materials
Manav Sadhna
Activity Centre
Yatin Pandya
Reclaimed Material « biome

14. A TYPICAL FILLER SLAB IN CENTRE FOR DEVELOPMENT STUDIES, TRIVANDRUM