This document discusses various methods of damp proofing in buildings. It begins by defining dampness as the access and penetration of moisture into buildings through walls, floors and roofs. Several causes of dampness are outlined like moisture from the ground, splashing of rain, and condensation. The ideal properties of damp proofing materials are described as being impervious, durable, dimensionally stable and flexible. Common damp proofing methods for foundations, floors, and walls are then explained involving bitumen, plastic sheets, and damp proof courses. The principles of effective damp proofing and different treatments for various building elements are provided.

1. Building Technology And Materials-I
Asso. Prof. SHARANABASAPPA.C.
M.Arch (ACPM), (PhD)
Asst. Prof. Abhay Aitwade
B.Arch
Indapur College of Architecture
INDAPUR

2. DAMP PROOF COURSE
(DPC)

3. Dampness a common
problem in buildings.
It refers to access and
penetration of moisture
content into buildings
through its walls, Floors,
roof etc.
It is important to take measures to prevent dampness.
Such measures is called damp proofing.
 Water proofing is a treatment of the surface or structure in a building
to prevent leakage.

4.  Moisturefromground:-Thematerialsusedfor thefoundationand floorsabsorbmoisture
fromthesoil andit risesupthesurfaceof thebuilding,
 Splashingof rain:-Whenrainsplasheson externalwallsdampnessmay entertheinterior.
 Exposedtopwall:-dampnessentersfromthetopif thetopsof parapetwallsarenot given
sufficient damp proofingcourse.
 Condensation:dampnessis causeddueto condensationof atmosphericmoisture,deposited
on walls andceilings.
 Constructiondefects:-
Improperplanning,
lack of proper slope inroof,
defectivepipefittings,
improperly sealedconstructionjoints
are constructivedefects.

5.  Ugly patches on walls and ceilings.
 Plaster softens and crumbles.
 Materials used for wall decorations are damaged.
 Stones ,bricks and tiles disintegrate due to efflorescence.
 Floor finish may be damaged
 Woodworks decays due to dry rot.
 Metal components of building corrodes.
 Electrical fittings are damaged,
 Dampness leads to
breeding of mosquitoes, growth of
termites and germs carrying
diseases such as tuberculosis,
it also aggravates asthma.

6. Requirementsofidealmaterialsfordampproofing:-
Theyshouldbe:-
 impervious.
 Durable
 Capable of bearing the load
 Dimensionally stable
 Flexible
 Free from sulphates, chlorides and
nitrates.
 inexpensive

7.  Hot bitumen :-hot bitumen,3mm thick may be applied on
bedding of mortar or concrete.
 Mastic asphalt:-semi rigid material obtained by heating asphalt
with sand and mineral fillers. It is laid on mortar or concrete
bed.
 Bituminous felt:-flexible material available in rolls. It is laid on
flat mortar finished surfaces.
 Metal sheets:-sheets of lead, copper and aluminum may be
used membranes in damp proofing. Lead is the most ideally
suited material.

8.  Combination of sheets and felts:-economical and drable damp
proofing sheet is obtained by sandwiching a lead sheet and bituminous
felt.
 plastic sheets:-a relatively cheap method of damp
proofing is by laying 0.5-1.0mm thick plastic sheets
made of black polythene. This is not a permanent
method.
 Bricks:-quality bricks absorbing water less than 4.5% of their weight may
be used for damp proofing. These bricks are laid in 2- 4 courses in cement
mortar.
 Mortar:-cement mortar in the ratio 1:3 is used for bedding layers over
damp proofing course. It may be mixed with slaked lime to improve its
workability.
 Cement concrete course:-a cement concrete course of proportion
1:2:4 and thickness 75-150mm is laid on masonry at plinth level.

9. General principles to be followed in damp proofing
are:-
 Mortarbedpreparedtoreceivedamp-proofcourseshouldbeleveled.
 Thehorizontaldampproofingcourseshouldcoverthefullwidthof wallexcluding
rendering.
 If sheetsormasticasphaltareused,thegapshouldnotbelessthan100mmat anypoint.
 At jointsandcorners.Dampproofcourseshouldbecontinuous.
 Dampproofingcourseshouldnotbekeptexposedonthewallsurface.
 At verticaland horizontaljunctions,dampproofcoursesshouldbecontinuousand a
cementmortarfilletofabout75mmshouldcoverjoints.

10. Different types of treatments are used for preventing dampness in diff
parts of the building:-
 Foundations:-this is method of protecting foundations of
outer walls. An air drain is constructed parallel to the
wall.
The drain is covered with
RCC slab, and gratings are
provided at regular intervals,
horizontal and vertical damp
proof courses are also provided.

11.  Treatment forfloors:-
if there is no damp soil, a layer of coarse sand,75-100mm
thick is provided over entire area under the flooring. Then
1:4:8 concrete of 100mm thickness is laid. This layer serves
as DPC. the usual flooring is provided over this,
If soil is wet, a membrane DPC is provided over the floor
area, over
which
a layer of flat bricks
is laid.
The usual flooring is
then provided.

12.  Treatment forwalls:
 the plinth level should preferably be 450mm above ground
level.DPC should be provided over a concrete bed of thickness
100-200mm.the top of the parapet should be provided with
capping over the DPC. the wall also needs DPC at the edge of
the roof slab.

13.  Providing foundation drains and DPC:-
to release hydrostatic pressure,trenches are made all around the
building and filled with gravels etc. such trenches may also be required
in buildings if the water table is at a higher level. The trenches lead the
water to a catch drain.Horizonta
vertical DPCs are provided in
the walls and foundation concrete
land
.

14.  Providing RCC raft and wall slab:-
 if thewaterpressureis high,providinga drainagesystemwill not solvetheproblemeffectively.Insuchcasesthe
floorslabandwallmay be preparedrightthroughtheRCCstructureandDPCis appliedonit.

15.  Asphalttanking:-
also known as membrane waterproofing.
Construction of horizontal layers :a leveled course of mass
concrete is laid for the flooring area ,over which a 30 mm
thick DPC in form of asphaltic layer is provided a protective
layer of cement screed, concrete or a layer of brick work is
laid over the asphaltic
layer, after which the
flooring is prepared.

16. constructionofverticalface:-
A vertical DPC is provided on the external face of
the wall. The DPC consist of an asphalt layer of about 20mm built in
three coats. This is then protected with a wall of ½ brick thickness.

17.  Lime concrete terracing:-
The RCC roof is cleaned thoroughly and a
bitumen primer is applied ,3 coats of hot blown asphalt is then applied over which a specially
prepared lime concrete bed of 100mmthickness is provided. The surface of bedding is covered
with flat tiles. a convex corner
joint is made at the junction
with the parapet wall.

18.  Membrane waterproofing:-
 water proofing membrane may be prepared with mastic asphalt or plastic sheet.
It is provided in a number of layers from 2-7.in this method a layer of hot mastic
asphalt is applied on the clean roof surface. This is covered by jute cloth and
another layer of mastic asphalt is laid.
In case of plastic membranes, hot coating is applied with blown bitumen
between each layer. The top is usually finished with a course of flat tiles.
At the junction is properly sealed with the parapet. The membrane should
extend up to parapet or lead sheets should be inserted.

19. Water proofing compounds may be
grouped to 2:-
 Waterproofing admixtures:-these admixtures are in powder or liquid form.
About 2% of powders are mixed while making cement mortar. when the
finishing coat of mortar is provided, these compounds seal the pores in the
slab and make
them watertight.

20.  Waterproofing membrane system:-these
materials are available in the form of paints,
they may epoxy or elastomeric and may be
applied to roof slabs with rollers ,brush or spray.
a minimum of 2 coats are applied to get desired
waterproofing.

21.  Sloped RCC roofs are provided with tiles for
purpose of weather proofing. It is preferable to
use flat tiles fixed to roof.
If Mangalore tiles are used care should be taken.
continuous motor bands should not be provided
as reapers because in case rainwater entering
through broken tiles stagnates on the mortar
bands, leakage will occur. Hence mortar bands
supporting Mangalore tiles should be
discontinuous. before laying the tiles, the
possible leakage points should be checked and
identified.