This type of waterproofing is approximately 3 times
more expensive than the traditional brickbat type waterproofing and is normally
used for waterproofing of terraces and slopping roofs. Various colour
combinations and patterns can be obtained in this type of waterproofing.
Material required
Apart from the material required for brickbat coba
type of waterproofing, given below is the list of additional materials required
for glazed china mosaic type of waterproofing work.
·
Pieces of
the glazed tiles i.e. china mosaic.
·
Lime
·
Fine sand
·
White cement
·
Colour pigment
·
Saw dust
For 10 sq.m of the china mosaic work, the following
quantity of material is required (Excluding brickbat coba layer)
Sr. No.
|
Material
|
Approx. Quantity
|
1.
|
Pieces of glazed tiles
|
135 kg.
|
2.
|
Lime
|
1.30 bag
|
3.
|
Fine sand
|
0.45 cum
|
4.
|
Grey cement
|
2.00 bag
|
5.
|
White cement
|
0.5 bag
|
Surface preparation
Chisel the extra mortar accumulated on the terrace,
using a chisel and hammer.
Clean the terrace thoroughly with water.
Add one bag of cement to hundred liters of water. Stir
the mixture to get a consistent cement slurry. Spread this slurry on the
terrace and allow it to penetrate uniformly over the cleaned surface.
Check the grading of the sand and its silt content
before using it for water-proofing.
Check the terrace door level and ensure that enough
margin (approximately 15cm) for water-proofing is left from the bottom side.
Check the level marked with red chalk on the parapet
wall, all around.
Ensure that the rainwater pipe outlet is bent in the
correct position.
Stack well burnt brick bats on the terrace.
Check M.S. tray required for the mixing of mortar.
Ensure that provision for plastic paper/tarpaulin is
made to protect the water-proofing from occasional rains.
Soak brick bats in water before use.
Preparation for brickbat coba terrace waterproofing.
Fix (line dori) in a slope 1:150, starting from the
lowest point of rainwater down-take and by keeping a minimum thickness of 65 mm
(2x1”/2), below the rainwater outlet.
Fix brickbats in cement-mortar layer of 1:6 proportion
in a slope of 1:150 with the waterproofing compound.
Fill the cement-mortar 1:4 with water-proofing
compound in the brickbat joints.
If the work is incomplete at end of the day and joint
is required for the next day’s work, provide brickbats in staggered manner and
avoid continuous horizontal joint of the mortar.
Fix small pieces of brickbats along with 20 mm (3/4”)
metal for coving of watta (rounding) at the bottom of the parapet wall.
Special care should be taken for achieving the round
shape near the rainwater pipe.
Block the rainwater outlet with gunny bags, to avoid
cement slurry from entering in.
Cure the brickbat coba coat for at least seven days.
Preparation for final coat terrace waterproofing
Spread cement-mortar in 1:4 proportion, along with
water-proofing compound over the brick bat coba.
Press the cement-mortar with a ruler of length of 2 m.
Level the surface with a wooden float, keeping 25 mm
(1”) thickness.
Apply thick cement slurry over the levelled surface
along with the water-proofing compound for a smooth finish (ghotai).
Polish the surface with metal float, i.e.,(polish
patra)
Make vertical and horizontal lines at an interval of
30 cm x 30 cm (12”x12”), using a cotton line dori of minimum 3mm thickness; so
as to avoid cracking of the top layer.
Make the projected edge (kani) between the parapet
plaster and the watta on the second day.
Clean and cure the final coat for 21 days with a least
6” water standing on the water-proofing.
Work procedure for glazed china mosaic type
waterproofing for terrace.
The roughened top coat of brickbat coba is cleaned and
washed properly.
Lime mortar made from the lime and fine sand in
proportion of 1:5 is spread uniformly on the surface with a thickness of 20 mm
to 25 mm uniformly. This is left to harden for a day.
This bed (machan) is checked for levels and slopes.
Design pattern, if any, is marked over this bed with
the use of cotton line string (dori).
Water is sprinkled on this bed (machan) and dry cement
is spread on the work area for 15 minutes. Pieces of china mosaic are then
pressed and fitted in position. The joints between these two pieces shouldn’t
exceed 3 to 4 mm.
After laying of the china mosaic pieces, they are
hammered with wooden mallet to achieve a uniform surface.
The surface is cured for at least 3 days.
If white or coloured joints are required, then the
grey cement joints are raked and white cement or colour cement slurry is
applied with a small trovel over the surface for joints of a matching colour.
Completed work is then cured for 15 days.
