Balcony/ Dry Terrace/ Attached Terrace Waterproofing


This standard operating procedure enumerates the scope of Waterproofing work in toilets to be executed in Tower area as specified in the approved drawings.


The respective Tower-in-charge is responsible to execute the work as per procedure.

Safety & protection:

PPEs like safety belts at height, helmets, safety goggles etc. should be used properly. 

Ensure the working area is kept clean for easy access.

Proper illumination to be provided during the work, if required.

Educate the workmen through pep-talk meeting. 

Preparatory works:

Cleaning of sunken slab base and sides of beams shall be carried out as regards all those materials, mortar, oil etc. thoroughly by wire brush and the area shall be washed clean.

PVC sleeves/ shuttering box used to made cutout should be removed.

Sunken slab should be filled with water and next day should be inspected for leakages.

If Leakages found, then cracks should be open out by making grove and pressure grouting by socket should be done. After completion of treatment sunken slab should be again recheck for any leakages.

Work method for Waterproofing:

Base coat using cement, sand and 10mm aggregates in proportion 1:3:1 with waterproofing compound (Fosroc Conplast X 421 IC) @ 150ml per bag of cement shall be applied over top of base slab of sunk. Maximum thickness of base coat shall be 25mm.

Base coat shall also be applied to the sides of the toilet sunk up to one foot above the finished floor level (F.F.L) of the adjacent floor. 

Curing of base coat shall be done by ponding for 3 days and checked against leakage. Leakage, if observed shall be rendered with reapplication of base coat to ensure no leakage.

 Floor traps and plumbing lines shall be installed, Slope of 1:100 shall be provided. Floor trap shall be fixed with respect to finished floor level (F.F.L) of the terrace.

Area of pipe which is going through the hole / opening provided in Slab should be made rough by applying cement solvent and sprinkling crush sand over it so that bonding between mortar and PVC pipes will be ensured.

AAC Block bats / brick bats should be made wet thoroughly for about 15 minutes prior to their placing.

Cement mortar in 1:4 proportions should be prepared and laid on slab. Mortar mixed shall be used within 1Hour of preparation.

 Pre-soaked AAC Block bats / brick bats shall then be laid in straight / radial, by inserting AAC block bats to a depth of about 15mm by light tamping with the help of mallets. Distances between adjacent layers of AAC Block bats / brick bats shall not exceed25mm.

 Application of AAC block-bats shall proceed from one corner. 

Mortar should be filled up to half height of brick bats and it should be cure for minimum 3 days. 

After curing is over, the surface shall be applied with a finishing coat of cement, sand and 10 mm aggregates in the proportion 1:3:1 with waterproofing compound (Fosroc Conplast X 421 IC) @ 150ml per bag of cement till top of brick-bats.

 Top coat shall be of neat cement slurry of adequate consistency and shall be done monolithic with topping of brick-bats.

Finished surface shall then be cured for at least 7 days by ponding and then tested for leakages, if any.


Water-proofing once done, shall not be broken or pierced. If water proofing is to be punctured, due care shall be taken to limit the damage to the restricted area. The cracks due to hammering shall not spread over the large area.

Repairing of the punctured area shall be done by using bonding agent and expansive grouts.


CBEC India