BUILDING CONSTRUCTION

LECTURE: 9 DAMP PROOFING

Mr. Manjally Ndow

OBJECTIVES
2

To state the different damp proofing
materials
 To illustrate the different positions of
damp proof courses.
 To explain the importance of hard core
 To state the significance of blinding


DAMP PROOF COURSES
3

Having considered the different types of
dampness and how they can occur in
buildings, it is important to know how to
prevent them from occurring in buildings.
 One of the best methods of avoiding
dampness in buildings is by installing damp
proof courses (DPCs) in different parts of the
building during the construction phase.


DAMP PROOF COURSES (Cont’d)
4

Damp proof course (DPC) is a barrier
of impervious material incorporated
into a wall or pier (platform) to
prevent moisture form moving to
any part of the building.
 Locate DPC at least 150 mm above
external ground or paving level.


TYPES OF DAMP PROOF COURSES
5







All materials used as damp proof courses should be
resistant to moisture content. A damp proof
course is cost effective and easily available.
The type of DPC to be used depends on the site
conditions on which the building is constructed as
well as the building construction rules.
However, most buildings in low-income countries are
not lined with damp proof courses. This could be as
a result of poor enforcement of building regulations
and also the cost of damp proof materials.

TYPES OF DAMP PROOF COURSES
6

The different physical DPCs include:
 Flexible materials such as hot bitumen,
plastic sheets, bituminous felts, sheets of
lead, copper,
 Semi-rigid materials such as asphalt
 Rigid materials such as impervious bricks,
stones, slates, concrete painted with
bitumen.


TYPES OF DAMP PROOF COURSES
7

CHEMICAL DPCS
 This technique uses liquid like
silicone compound which is either
introduced into the wall by simple
gravity or under pressure.
 The liquid will either fill the pores
of a material with water resistant
material (pore fillers) or line
them with a non-absorbent
surface to reduce capillary
attraction (pore liners).

POSITIONING DAMP PROOF COURSES
8

The first DPC can be placed before the floor
is laid or on the floor itself before the screed
or tiles are laid but the former is better.
 The next layers of DPCs can be put under the
windowsill and lintel. And if there is a floor
above, another DPC can be placed under it.
 Parapet walls and on top of wall plates
would also need DPC to be installed.


DAMP PROOF COURSE IN BRICKWORK
9

DAMP PROOF COURSE IN SLAB WORK
10

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Damp proof courses (DPCs)

PRINCIPLES OF HARD CORE
12

Hardcore application in the building
process is also as important as any of the
key stages .
 Hard core is a measure involving the use
of some large aggregates of stones
(granite) during the process of building
construction especially when
constructing foundation or floor area.


PRINCIPLES OF HARD CORE (Cont’d)
13

In the majority of cases, broken blocks or
bricks are used in this process, but are
not recommended due to their strength.
 Hard core is applied after the internal
part of the foundation or floor area have
been filled with some fine sands prior to
the application of iron rods or wire mesh
and concrete.


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IMPORTANCE OF HARD CORE
15

Strengthens or solidifies the base of the
building to resist the pressure of dead
and live loads acting on the building.
 Save cost of construction, i.e. the volume
occupied by the hard core if it were to be
concrete would have cost more.
 Reduces movement of water up to the
floor surface.


SIGNIFICANCE OF BLINDING
16







Before the concrete is laid it is important to blind the top
surface of the hard core.
The purpose of this is to prevent the wet concrete
running down between the lumps of broken brick or
stone, as this would make it easier for water to seep up
through the hard core.
To blind the top surface of the hard core a thin layer of
very dry coarse concrete can be spread over it, or a thin
layer of coarse clinker (powder) or ash can be used. This
blinding layer, or coat, will be about 50 mm thick, and on
it the site concrete is spread and finished with a true
level top surface.

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REFERENCE
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Rising damp and its control: A guide to
identifying the various forms of dampness
encountered in buildings and control of rising
damp through remedial action.
 The University of Nottingham Ningbo, China:
Division of Sustainable Development.


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