ROOF WATER PROOFING / TANKING

Liquid Wtaerproofing for bathrooms, kitchens and other tiled wet areas

Two component synthetic rubber, liquid waterproofing membreane . Which cures to form a resilient fully bonded elastomeric sheet. Tiles can be fixed directly to the cured membrane with tile adhesives. The use of metal lathing vertically is Optional.

Tools Required

Stiff broof, Steel plastering Trowel. and wet film thickness guage.

Surface preparation

All surfaces shoudl be clean and dry. irregularities greater than 3 mm should be removed or filled. masonary walls should be flush pointed or bagged.

All butt joints in gypsum cement boards should be taped with 50 mm reinforced adhesvie tape. All gaps > 6 mm should be filled with mastic selant allowing sufficeint time to cure before applicable of tape of membrane.

Application

Liquid membrane is best applied using a pour and trowel technique

cover the top half of the wall fi4rst. Use and adapted plasterres hawk or pour directly from the bucket onto the wall.

Fro the bottom half of the wall, pour the material directly from the bucket onto the wall or pour onto a clean area at the bottom fo the wall and trowel upwards.

Swipe and twrowel marks are aceptable as long as minimum thickness is maintained. excessive trowel marks will result in high adhesive usage or an eneven tiled surface. do no over work the material after it has been applied to the wall.

Always have the draingage pipe installed before the material is applied.

Additional adhesive support from metal lathing applied to walls is recommended.

Mr. Mohan,

Let us counter first the method to arrest existing leakages on Roof

diff. Reasons

1) Leakages from the join of two diff. slabs

case 1

Both slabs casted simultaneiously.  due to the law of heat during casting generated due to process of cement, the pours developed and result in leakages

Remedial method during construction is using debonding agent between the slabs, screeds

Case 2

Two diff. slabs casted at diff. time interval. here too debonding agent might had been used to make sure both slabs are bonded. and height diff. between two slabs

Solution

the best way is to cut a groove on the slab joint from top (approx. 20 mm) and use liquid polyruthene injected to seal the pours. (quality products available in Sika , Fosroc product range.

Epoxy selaants can be used for huge area.  for being economical. (gun grade)

allthough cementioius materials are avialable  but rather wont be effective as the purpose is to seal the pours developed between slabs which resulting in leakages.

Leakages on Roof.

Ultimate worst case is leakages direct from the slab surface, which is due to poor construction methodology adapted.

generally leakages occur on roof - from the joints

it can be joint of two diff. slabs, joint between column and slab, wall and slab

Good construction practices can counter this  worst nightmare for any house holder

Leakages from Roof

- Use  of  a liquid applied membrane which have the property of debonding and waterproofing between the slab and the roof screed.

- Proper overlapping on self adhesive membrane / torch applied membranes.

- Flashing

Hello Girish,

I am in the process of constructing my house in Pune and looking into proper ways for effective water-proofing. I have received following suggestions from one of my friends in this field & I need your opinion about it.

Option 1: BRICK BAT COBA 6" THICK AS PER SLOPE

Option 2: For flat surfaces - 3 mm thick moply reinforced polyster 4 Kg. gravel finish mat - Atatic polypropline membrane, Preferably - Texa india Ltd. For Sloping surface (a) water proofing membrane Moply FV 3mm preferably - Texa India Ltd (b) P & L of shingles with LPG torchon application for asthetic look

Option 3: Same as option 2 but with equivalent products from Pidilite / Dr FIXIT

Pls reply asap.

Considering the Hot climate in India,  we must consider using polystrene insulation on roof tops  and even between two layers of outer block wall.

this guarantee the temperature resistance and save your money in long term on air condition and help you keep your house cool.

A general specification for roof water proofing specially in hot climate like ours is as below

Membrane - flexible puncture resistant , bilogical and chemical resistant high performance reflective roof water proofing membrane cobinaing a spcial high density polythylene composite carrier film and a flexible self adhesive rubber/bitument compound

solar shield
solar shield shall be heavily textured aluminium sheet thickly coated ont eh udnerside with a self adhesive rubber/bitumen compound

Thermal insulation
Thermal insulation shall be either moulded/expanded polystrene or moulded extruded polystrene closed rigid foam board self fnishing. minimum density 32 kg / m3

Screeding
The roof surface to be water proofed shall first be rendered to falls and slopes by screeding.
The rcc surface shall be cleaned of all loose materials dirt, dust etc and 1:3:6 pcc screed of min. thickness 50 mm thickness shall be laid to falls and slopes as required and integrally finished smooth by trowelling.

the screed then be cured and dried. at corners 40 x 40 mm pcc (1:3:6) angle fillet shall be provided and cured.

Membrane application

Two layer built up roofing shall be fixed in accordance with the propreitary manufactures printed recommendations.
the stubstrata shall be dry and prepared to receive treatment.
Primer shall be applied as per mfg. recommendations
All laps shall run parallel to the slop in the roof and joints staggered with 100 mm side and 150 end laps.
second layer shall be laid in lengths not exceeding 8 mtr.
The grooves shall be sealed with approved tropical grade mastic sealtn or covered by snap on powder coated aluminium beading.

Sealants
Bituminous mastic shall be used for moulding into fillets. collars and tapes for sealing around pipes and irregularities
cold applied rubber bitumen mastic compound good for even trowel application.
mastic shall be of grade suitable for hot climate

polyruthane gun grade selant which cures with atmospheric moisture to form a flexible
water proof seal shall be used for flashing

Roof finishing.
The roof areas shall be covered with cement tiles