This PPT contains the description of damp proofing course

2. Dampness a common
problem inbuildings.
It refers to access and
penetration of moisture
content
into buildings throughits
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 buildingto
prevent leakage.

3. Moisturefromground:-Thematerialsusedforthefoundationandfloorsabsorbmoisture
fromthesoilanditrisesupthesurfaceofthebuilding,
Splashingofrain:-Whenrainsplashesonexternalwallsdampnessmayentertheinterior.
Exposedtopwall:-dampnessentersfromthetop ifthetopsofparapetwallsarenot
given sufficientdampproofingcourse.
Condensation:dampnessiscausedduetocondensationofatmosphericmoisture,depositedonwalls
andceilings.
Constructiondefects:-
Improperplanning,
lackofproperslopeinroof,
defectivepipefittings,
improperlysealedconstructionjoints
areconstructivedefects.

4. 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.

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

6. 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.

7. 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.

8. G
e
n
e
r
a
l
p
r
i
n
c
i
p
l
e
s
t
ob
e
f
o
l
l
o
w
e
d
i
nd
a
m
p
p
r
o
o
f
i
n
ga
r
e
:
-
 Mortarbedpreparedtoreceivedamp-proofcourseshouldbeleveled.
 Thehorizontaldampproofingcourseshouldcoverthefullwidthofwallexcluding
rendering.
 Ifsheetsormasticasphaltareused,thegapshouldnotbelessthan100mmatanypoint.
 Atjointsandcorners.Dampproofcourseshouldbecontinuous.
 Dampproofingcourseshouldnotbekeptexposedonthewallsurface.
 Atverticalandhorizontaljunctions,dampproofcoursesshouldbecontinuousanda
cementmortarfilletofabout75mmshouldcoverjoints.

9. Diff
eren
tt
y
p
e
so
ftreatmentsareu
s
e
df
orpre
v
entingd
a
m
p
n
e
s
sindiff partso
fthebuilding:-
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.

10. T
re
a
t
m
e
n
tf
orf
l
o
o
rs
:
-
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.

11. T
re
a
t
m
e
n
tf
orw
a
l
l
s
:
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.

12. Providing foundation drains and DPC:-
thewallsandfoundationconcrete
land
.

13. Providing RCC raft and wall slab:-
ifthewaterpressureishigh,providingadrainagesystemwillnotsolvetheproblemeffectively.Insuchcasesthe
floorslabandwallmaybepreparedrightthroughtheR
C
C
structureandD
P
Cisappliedonit.

14. A
s
p
h
a
l
tt
a
n
k
i
n
g
:
-
alsoknownasmembranewaterproofing.
Constructionofhorizontallayers:aleveledcourseofmass
concreteislaidfortheflooringarea,overwhicha30mm
thickDPCinformofasphalticlayerisprovidedaprotective
layerofcementscreed,concreteoralayerofbrickworkis
laidovertheasphaltic
layer,afterwhichthe
flooringisprepared.

15. constructionofverticalface:-
AverticalDPCisprovidedontheexternalfaceof
thewall.TheDPCconsistofanasphaltlayerofabout20mmbuiltin
threecoats.Thisisthenprotectedwithawallof½brickthickness.

16. L
i
m
e
c
o
n
c
r
e
t
et
e
r
r
a
c
i
n
g
:
-
 T
h
eR
C
C
roofisc
leanedthoroughlyanda bitumen
primerisapplied,
3coatso
fhotb
l
o
w
nasphaltisthenappliedo
v
e
rw
h
i
c
haspeciallypreparedlimeconcretebedo
f
1
0
0
m
m
t
h
i
c
k
n
e
s
sispro
vided.T
h
esurfaceo
fbeddingisc
o
v
e
re
dwithflattiles.ac
o
n
v
e
xcorner
 jointismadeatthe
junction withtheparapet
w
all.

17. M
e
m
b
r
a
n
ew
a
t
e
rp
ro
o
f
i
n
g
:
-
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 th e 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.
A t the junction is properly sealed with th e parapet. The membrane
should extend up t o parapet or lead sheets should be inserted.

18. Water proofing compounds may begroupedto2:-
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.

19. 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.

20. SlopedR
C
Croofsar
epr
ovidedwithtilesforpurposeofweatherpr
oofing.Iti
s
preferabletouseflattilesfixedtoroof.
IfM
angalor
etilesar
eusedcar
eshouldbetaken.contin
u
o
u
sm
o
t
o
rb
a
n
d
sshouldnotbe
pr
ovidedasreapersbecauseincaserainwaterenteringthr
oughbr
okentiles stagnateso
n
themortarbands,leakagewilloccur
.H
e
n
c
emortarb
a
n
d
ssupportingM
angalor
etilesshould
bediscontinuous.beforelayingthetiles,thepossibleleakagepointsshouldbecheckeda
n
d
identified.