WATER PROOFING

WATER PROOFING

WHAT IS WATER PROOFING?

Waterproofing is a method by which an item is made resistant to damage by water.

A mortar or concrete is considered impermeable when it does not permit passage or flow of water through its pores or voids.

 Waterproofing is the formation of an impervious barrier which is designed to prevent water entering or escaping from various sections of building structures. Internal areas that are waterproofed include bathrooms, shower recesses, laundries and toilets. Whilst an External area waterproofed extends to roof, terrace, basement floor, exterior surfaces of walls, balconies, retaining walls and swimming pools.

INTRODUCTION

Waterproofing is one of the most important parameters considered in the construction of building and structures to prevent leakages, dampness etc and making the structures durable.

Waterproofing is defined as a treatment of a surface or structure to prevent the passage of water under hydrostatic pressure.

In waterproofing, we will discuss on waterproofing terraces, balconies and flat roofs.

Also we will discuss on both waterproofing of old structures andwaterproofing of new structures.

The aim of this is to reduce the frequency of problems which may be traced back to incorrect design specifications and problems caused by incorrect installation techniques.

Water will cause serious and continuing problems in buildings and building materials unless its effect is understood and provided for in the construction details.

Most of the water leakage problems, more than 50% of claims for damages involve infiltration, while more than 60% of these claims are due to problems with the waterproofing layer.

For waterproofing latest advanced technologies are being used worldwide.

It is caused by poor detailing, poor workmanship, inferior materials or any combination thereof. 

WHY WATER PROOFING IS REQUIRED?

Seepage or leakage is percolation of water through the voids or spaces of the material.

Seepage may occur through defective water pipes, sanitary fitments or drainage pipes, etc.

To overcome this problem of seepage, waterproofing of structure is necessary.

Waterproofing helps to maintain the beauty and increase the life of the structure

NEED OF WATERPROOFING

Leakage

The water leakage term in buildings is used to mean the coming out of water from components like walls and floors of the buildings.

Dampness

Moisture is present in the materials of the building itself, and the air within the building.

Moisture movement

To effectively weather-proof our buildings, we need to understand how and why water behaves as it does. 

REASONS FOR WATER LEAKAGE

Defects due to poor maintenance

§  Filling of joints

§  Joints in floor of toilets

§  Improper use of toilets

§  Replacement of traps

Defects in construction

§  Defective concrete

§  Door frame joint near toilet

§  Plumbing

§  Push cocks

§  Rain water spouts

§  Sill to terrace door

§  Water-proofing of terrace

Defects in design

§  Design of floor slab

§  Design of rain water spouts

§  Fixing of nahni traps

§  Relief valves

§  Slope of terrace slab

TYPES OF WATERPROOFING

SHEET MEMBRANE WATERPROOFING (SLAB)

Lose laid – PVC, HDPE, etc.

Bonded – self-adhesive, hot applied.

PROCEDURE FOR ROOF SLABS

The concrete surface shall be cleaned thoroughly of all laitance, loose particles, dust, grease, etc.

Defects like honey combing ,cracks ,if any ,to be repaired by bonding agent enriched cement-sand(1:4) mortar after applying sika raintite enriched cement slurry.

Surface is then thoroughly saturated with water and should be in surface saturated condition.

Apply one coat of cement slurry enriched with sika rainite (SR:W:C=1:2:3, all by volume) on the roof slab surface and  also up to a height of 150mm on vertical surface of the parapet wall.

On drying of first coat, apply second coat of similar cement slurry admixed with sika rainite for bonding effect.

While the second coat of cement slurry with sika raintite is still tacky, a screed concrete of mix 1:1.5:3 admixed dosage of plasticizer shall be 0.2% on weight of cement, the concrete shall be cured with water in usual manner and continued for 10 days.

LIQUID WATERPROOFING

Liquid Waterproof membranes consist of polymers and bitumen.

These membranes are extensively used for the purpose of sealing terraces, balconies, bathrooms, etc.

Finally, these waterproof membranes have high adhesive property

BENTONITE WATERPROOFING

Bentonite is a type of clay having the unusual characteristics of cohesion, binding, sealing, and thickening.

It is usually grey in colour and when processed has the consistency of fine powder, similar to cement or flour.

BOX TYPE WATERPROOFING (RAFT SLAB & BASEMENT WALL)

Raft slab

20 mm thick cement mortar in CM 1:4 admixed with chemicals shall be laid on the prepared surface.- 15 to 20 mm thick rough kota stones are laid over cement mortar bed with 15 mm gap between two kota stone.- Joints between stone slabs are raked and cleaned. cement grout is filled in joints.- A protective layer of 20 mm cement mortar is laid over the stone slab.- over that reinforcement with proper covering is placed.- after pouring of raft slab, at the Top surface, zigzagnozzling is done for grouting purpose.

Basement walls

 Rough finished low porosity stone slabs 15-20mm thick are fixed with the help of cement paste applied on the internal face of stone slabs, leaving a gap of 15 to 20 mm between the external face of RC wall and internal face of the stone slabs. The stone slabs are fixed side by side without leaving any gap between the edges. In order to fix the bottom most layer of stones a grooves is made in top layer of base treatment and stone slabs fixed in it to ensure the water tightness at the junction of wall and raft.- Maximum 2 to 3 layers of rough stones are laid at a time.-15mm thick cement plaster in CM 1:4 is applied to the external face of rough stone.- The gap between the wall & stone is filled with chemical admixed cement grout, which forms an impermeable monolithic layer.- Holes are drilled on the inner face of RC wall at 1.2mc/c over the entire wall surfaces in the grid pattern.-GI or PVC nozzles are fixed in these holes with cement and allowed to set. -Cement slurry admixed with non-shrink expanding grout should be injected throughout the network of nozzles by low pressure hand pump until refusal.- The protruded end of the nozzles shall be cut and sealed off after the grouting operations are over.

WATERPROOFING MATERIALS

Acrylic based polymer coating

Variations of temperature causes micro cracks in concrete and these micro cracks propagate with time.

Also structural inadequacy or failure to adhere to poor detailing of reinforcement, or unequal settlement etc is some of the additional reasons for development of cracks in concrete members.

In such situations a membrane forming waterproofing material is ideal. The membrane should be tough, water resistant, solar reflective, elastic and durable.

Chemical DPC for rising dampness

Often old buildings are not provided with a DPC.

The water from the ground rises due to capillary action. This water brings with it dissolved salts and chemicals which affect the durability of the structure.

Now we have materials that can be injected into wall at appropriate level to seal the capillaries and thereby to stop upward movement of water.

Waterproofing adhesive for tiles, marble, and granite

Silicon based water repellent material

When for aesthetic purpose transparent water proofing treatment is required then silicon based water repellent materials are used. These materials form a thin water repellent film on the surface.

These types of waterproofing materials are used in many monumental stone buildings and old places so that the original look of the stone masonry can be maintained.

Injection grout for cracks

It is one of the most powerful methods commonly adopted for stopping leakages in dams, basement, swimming poolsand construction joints and even in leaking roofs.

This method is useful for gravity as well as pressure grouting and is a powerful method for strengthening and waterproofing of unhealthy structures.

Joint sealants

Joints in buildings, bridges, roads and airfields pavement are inescapable. They may be expansion joints, construction joints, or dummy joints.

Such gaps should be effectively sealed using sealants. Now-a-days we have modern materials like polysulphide sealants and gun applied silicon rubber sealants.

These are manufactured and sold under various trade names, and are available in powder or liquid form, e.g.: “SAHARA”, “POZOLITH”, “AQUELLA”,  “ZILICON”, “ANTI-HYDRO”

PRECAUTIONS

§  See that all the material used is of good quality.

§  See that the traps and release pipes are fitted properly before brick-bat coba coat.

§  See that all the bricks are well soaked in water before use.

§  Observe minimum gap between the brickbats.

§  Check the slope in brick bat coat, towards the tap.

§  See that waterproofing compound is mixed in mortar at every stage of work.

§  Observe proper finishing near spouts.

§  Check each stage by flooding it by water for leakage.

§  Cure the surface without interruption.