06-07-2012, 04:22 PM
Brick bat Coba Water Proofing on Terrace
Materials :
The aggregate for brick bat coba shall be broken from good and thoroughly well
burnt bricks. These shall be approved by the Engineer-in-charge before use.
Brick bat coba shall be in Cement Mortar 1:2
Laying :
The concrete surface shall be thoroughly rubbed, cleanced of all set mortar, all dirt
and dust and slightly wetted. The brick aggregate shall be soaked in water before mixing
with lime. The brick bat coba shall be laid in an even layer and to the required thickness and
slope so as to form ridge, hip or valley line as may be necessary and as indicated in the
drawing or as directed by the Engineer-in-charge. The compaction shall be started
immediately kept wet by sprinkling water observing the following
precautions :
a) Brick bat coba shall not be rammed with heavy iron rammers as brick aggregates are
likely and rapidly with wooden beaters to get the required compaction and to obtain
complete integration of brick bats and lime.
b) White beating, fresh fracture may take place which may cause absorption of water
from the mortar. Additional water may be sprinkled with beating in such causes as
considered necessary by the Engineer-in-charge. The beating work shall continue for
atleast 7 days.
c) The average thickness of coba shall be as specified in the items and the top of the
coba shall be given slope or made level and edges taken into the brick masonry
parapet or rounded off at junctions (vatas) as shown in the drawing and as directed
by the Engineer-in-charge.
Cement Based Waterproofing of roof terraces
General :
The waterproofing treatment shall be essentially a cement based waterproofing
treatment similar to that of M/s Indian Waterproofing Companys CETROOF or any other
approved waterproofing treatment. The waterproofing treatment shall consist of providing
cement slurry mixed with waterproofing compound, at desired proportions including
grouting the cracks and crevices with cement slurry mixed with waterproofing compound,
laying brick bats over cement mortar bedding to the required slopes for roof drainage, filling
and grouting the joints with cement mortar, finishing the surface smooth/chequered with
cement plaster mixed with waterproofing compound etc. as directed.
Preparation of Surfaces :
All the rubbish, debris and other materials left over by other agencies will be got
removed by the Department through other agencies. After removal of this rubbish, debris
etc. the surface to receive the waterproofing treatments shall be thoroughly cleaned with
wire brushed including removing of scales and laitance, set mortar etc. by the waterproofing
contactors. If any honey combing including cracks and crevices are observed at coloumn
junctions / and elsewhere, the same shall be grouted with cement slurry mixed with
approved water proofing compound.
Treatment :
The waterproofing treatment shall be generally as per manufacturers own
specifications, method and procedure. A typical cross section of the waterproofing treatment
shall generally consist of the following:
1. Applying cement slurry mixed with waterproofing compound for the entire surface to
be treated.
2. Laying of broken brick bat of required thickness over cement mortar bedding to give
proper roof drainage, joints grouted with cement mortar with waterproofing
compound.
3. Laying of joint less cement based waterproofing cement mortar layer of average
thickness as specified in the item.
4. Final rendering to give a smooth finish of cement colour with false lines at 300 X 300
mm or nearer convenient dimensions. Tenderer shall give complete details of waterproofing treatment proposed by him, in writing viz. details including roof fill
materials, waterproofing compound, minimum and maximum thickness etc. for
effective supervision of the departmental Engineers, while the work is executed at
site.
The contractor shall ensure that sufficient slope for effective roof drainage is provided
within the average thickness of waterproofing treatment proposed by the contractor. Incase
the average specified thickness of treatment exceeds, the fact shall be specifically brought
to the notice of the Engineer-in-charge, before adopting to extra thickness.
The rain water down take pipes if any, shall be fixed by the other agency prior to
commencement of waterproofing operation. Curing of the finished surface by ponding shall
be done for 7 days atleast.