Low-cost building materials and techniques can significantly reduce construction costs. Some examples discussed are: 1. Using filler slabs which replace 20% of concrete in slabs with low-cost materials like tiles, reducing material and steel costs by 30%. 2. Rat trap bond bricklaying which places bricks vertically, creating a cavity that reduces brick/mortar usage by 25-40% while maintaining structural integrity. 3. Careful site selection, soil testing, minimizing wall surfaces and planning construction to avoid changes can optimize costs. Using machinery efficiently and estimating labor needs can also reduce expenses. Planning is key to utilizing low-cost alternatives without compromising quality or safety.

1. AR-323
Low-cost
building
materials
and
techniques
Semester VI 2021-22
Department of Architecture, Planning & Design
Indian Institute of Technology, BHU, Varanasi 16-Feb-2022

2. Low-Cost Building
Materials

3. Spectrum of building cost
Affordable Housing for
LIG
1
Low-Cost
Buildings
2
RCC Buildings
3
Villa
4
Mansion
5

4. Raw Material Source for Low-Cost Building Materials
Natural
Man-made
INDUSTRIAL WASTE
Waste product of
any industry
INDUSTRIAL BY-PRODUCT
Available as a by-
product of any industry
AGRICULTURAL BY-PRODUCT
Obtained from
Agriculture
NATURAL
Freely available in
nature

5. Material Selection Criteria
Locally
Available
Bio-
degradble
Recylable
Enegy
Efficient
Non-Toxic
Salvaged
Low-embodied
energy
Non-polluting
Reused

6. Enegry in buildings

7. Proportion of operational and embodied energy over the 50-year life of a
typical brick veneer house

8. Embodied energy
1. Embodied energy is a calculation of all the
energy that is used to produce a material or
product, including mining, manufacture and
transport.
2. To achieve a home that is truly low energy, it is
important to consider embodied energy when
choosing materials and construction systems.
3. Different types of materials and construction
systems will have very different levels of

9. Embodied energy
3. It is not just a matter of choosing low embodied energy
materials. A house built with low embodied energy materials
may require more operational energy to run the home (for
example, for heating and cooling).
4. balancing the embodied and operational energy is
essential.

10. Embodied energy
The total embodied energy of a building is the total energy
needed for:
•production of all the materials used in the initial construction
(initial embodied energy)
•production of all the materials used in repairs or renovations
over the life of the building (recurrent embodied energy)
•transport of materials to site
•energy used on-site during construction, repairs or
renovations.

11. Embodied energy

12. Low-Cost Building Materials
as a Replacement
• A Low-Cost Building Material
should be a replacement of
any commonly used building
material based on its
characteristics of tensile
strength or compressive
strength or any other attribute.

13. Low-Cost Building Materials
as a Replacement
• Bricks: Unburnt bricks, mud bricks, fly
ash bricks

14. Low-Cost Construction
Techniques

15. Steps in a building construction
• Building Site Selection and Land Acquisition
• Finalization of Built-Up Area
• Building Design
• Building Construction
• Substructure
• Superstructure
• Services
• Occupation

16. Lifecycle of a building

18. Questions
to Ask
Is it necessary?
Can it be optimized?
Is there any alternate
technique?

19. Low-Cost Construction Techniques as a Replacement or Alternative

20. Filler slab
• Filler slab is alternate slab construction
technology where part of concrete in
bottom of slab is replaced by filler material.
The basic principle is that the concrete in
bottom half of RCC slab is structurally not
required as concrete acts as compression
material which is required in top half
portion of slab. So, this portion concrete is
replaced by low cost, light weight filler
material like mangalore tile, clay pots etc.

21. Filler Slab

22. Advantages of
using filler slab
roof
• Concrete required in this technology
is about 20% less than conventional
slab construction. Due to reduced
concrete, self weight of the slab is
reduced and thus about 30% less
steel is required, without
compromising strength of the slab.
This technology was used by
Architect Laurie Baker in Kerala
extensively.

23. Things to consider about
filler material
• Filler material should be inert. It should not
react with concrete or steel It should be
light weight, low cost and preferably locally
available Size of filler material should be
such that it fits in bottom half of the slab
and structural grid of reinforcement Using
material with good thermal insulation
properties like clay will provide thermal
comfort inside the room The filler material
will be seen as part of ceiling so shape and
finish of the material should be as per
desired aesthetics

24. House constructed with
filler slab technique

25. Principles for Low-Cost Construction
Techniques
• Alternate or Replacement of a commonly used construction
technique.
• Alternate low-cost techniques must not compromise on the structural
characteristics. It should be comparable with the commonly used
techniques.
• Long term impact of the techniques must be assessed.
• The alternate technique should be cost-effective in terms of energy,
time, labor and materials.

26. Rat trap bond
• Rat trap bond is a brick masonry
method of wall construction, in
which bricks are placed in vertical
position instead of conventional
horizontal position and thus
creating a cavity (hollow space)
within the wall. Architect Laurie
Baker introduced it in Kerala in the
1970s and used it extensively for
its lower construction cost,
reduced material requirement and
better thermal efficiency than
conventional masonry wall,
without compromising strength of
the wall.

27. Rat trap bond
Objectives
• The main objective of utilizing this type of masonry bond is
to decrease the number of bricks and amount of mortar
required as compared to the English/Flemish bond.

28. Rat Trap Bond: Construction
• The bricks are placed in vertical position, so
that 110 mm face is seen from front elevation,
instead of the 75mm face (considering brick
of standard size 230 X 110 X 75 mm). Since
width of wall remains 230mm, an internal
cavity is created. This is where approximately
30% Material (brick and mortar) is saved and
thus overall construction cost is reduced.
Cavity provides effective thermal and sound
insulation. This makes rat trap bond energy
and cost-effective building technology.

29. Rat Trap Bond: Construction

30. Advantages of using rat trap bond
• Requires approximately 25% less bricks and
40% less mortar than traditional masonry.
• Reduced material requirement results in
considerable cost saving.
• Strength of wall is not compromised; it
remains same as traditional masonry wall.
• Cavity induced in wall provides better
thermal insulation, resulting in cooler
interiors during summer and warmer
interiors during winter.
• All vertical and horizontal reinforced bands,
lintels (for standard size openings),
electrical conduits are hidden inside wall,
resulting in better aesthetic appearance
without plastering (exposed brickwork).

31. Rat Trap Bond: Considerations
• Bricks should be of good quality with consistent
size and straight edges First layer (bottom)
and last layer (top) of the wall should be solid
(without cavity).
• Layer at sill and lintel levels of opening and
sides of opening should be solid (without cavity)
for fixing frames.
• Reinforcement bars can be put in vertical cavities
at corners and around openings to improve
earthquake resistance. Reinforcement bars can be
put in horizontally to make lintels and to improve
earthquake resistance.
• Electrical conduits and plumbing pipes, with prior
planning, can be put inside cavity for better

32. Rat Trap Bond:
Considerations

33. Rat Trap Bond:
Disadvantages
• This kind of construction is not able to resist sound.
Thus, the soundproof wall is not feasible this way.
• Mason must be careful while placing bricks. More
care must be adopted while designing the wall length
and heights for the structure.
• Particular attention and care to be allotted while
constructing and designing rat trap bond masonry.
• Pre-training is needed if workers are not aware of
this pattern of bricklaying, if not feasible, then
employed experienced workers; hence the cost of a
worker may rise.
• A rat trap brick wall requires cleanness of the
external surface (if not plastered) every three years.

34. FAQs: Rat Trap Bond
• What is rat trap bond in brickwork?
• Rat Trap Bond is a type of brick bonding in masonry work where bricks are laid vertical in
a direction to create a cavity within the bricks instead of laying the bricks horizontally. It
is sometimes also called a Chinese Bond.
• Is rat trap bond load bearing?
• Having a strong structure Rat Trap Bond can be used in the load-bearing structures as
well as in non-load bearing structures such as partition walls.
• Rat Trap Bond
• Rat Trap Bond is a modular type of brick masonry bond in which the bricks are laid in a
vertical position which creates a cavity in the wall while assuring the same wall thickness
as in the case of the normal brick masonry wall. It is also known as a Chinese brick bond.

35. Selection of Plot
• Go for a roadside plot where transportation facility
and communication to every necessary center is
possible. Because that
can reduce your transportation cost for a lifetime.
• But many sellers are there who take
the opportunity of high demand and sell
the roadside plots at a very high price. So be careful
while choosing the plot. If you are getting it a little far
from the main road then it is ok.

36. Conduct Soil
Test
• Soil test is a
much essential part of
the construction. Different
types of
soil behaves differently.
• If the soil quality is not good
(for construction) or if it
is loose soil, then it will incur
a huge foundation cost.

37. Confirm Electrical and
Water Supply in Area
• If there is no electric and water
connection near the plot then
applying for a separate connection
near the plot and getting
separate connection for plumbing,
could be an expensive affair.

38. Selecting Shape of
House
• The shape of the house also contributes to
increasing the cost of construction. When
the size of the home increases it increases the
surface area and ultimately the cost
of construction. A house should be designed
in such a way that it should reduce the surface
area and thus reduce the cost.

39. Reduce Number of Wall
• Make the home more spacious by
reducing the number of walls. It
ultimately reduces the surface area
and decreases the cost. It
also permits natural light to
enter the house and decreases the
number of electricity expenses.

40. Prepare Structural Drawings
• Preparing structural
drawings for the house
is essential.
• From this structural
drawing how much amount
of reinforcement, sand, cement,
and bricks will be required can
be calculated in advance. And if
this is done accurately then
there is a chance of saving lots
of money.

41. Plan Ahead : Do not Make Change After Construction Starts
• Sometimes people approve one
plan before construction and
during construction, they
suddenly change their plan.
• This is one of the
major reasons which
again increases the
construction cost. Try
to avoid this thing unless & until
it is necessary.

42. Saving in Labour Cost
• Labour cost is also a large part
of the construction which can
not be cut easily. Try
to calculate the works in
hours how much labor will
be required to finish work and
how much time. In this way you
can save your cost by
estimating the labour cost

43. Saving in Machinery Cost
• Construction machines are
mostly hired on a rental
basis and their rental cost are
high.
• Try to
take maximum advantage
of construction machinery in
a calculated way by
which construction costs can
be saved.