Waterproofing and Weatherproofing materials
Waterproofing can be defined as treatments to the surface with a substance, which will prevent water from going through it. Waterproofing prevents the entrance of water that is under pressure by forming a continuous membrane around walls, through concrete footings and under concrete floor slabs.
There are lots of conventional and unconventional methods practiced for waterproofing in construction field. Old methods like brick bat–cobba, cement–lime based treatments, bituminous coatings are still practiced successfully. But the development of modern construction material and technology, the concept of waterproofing has changed tremendously. Nowadays integral waterproofing compounds are admixed into the plastic concrete.These materials impart water repelling (damp-proofing) to concrete, may reduce moisture migration through capillary reaction. Surface coating application is another known method generally followed.
The need for waterproofing
-Water may leak through cracks, expansion joints or other openings in walls and roofs, or through cracks around windows and doors.
-Also, water may seep through solid but porous exterior materials, such as masonry.
– Whether thrust against and into a building by a flood, driven into the interior by a heavy rain, leaking from plumbing, or seeping through the exterior enclosure, water can cause costly damage to a building.
– The water proof membrane thus used must prevent the water from entering pores and voids in the structure of building
Types of waterproofing membranes
There are generally two types of waterproofing membranes – sheet membranes and liquid membranes. The nature of the problem to be addressed determines which type of membrane to be used.
The purpose of sheeting membrane is to completely cover any imperfections in the substrate or background. They are numerous and include:
– Metal sheets in the form of lead, copper or stainless steel flashing or trays.
– Multilayer bituminous paper system with gravel topping for protection.
– Butyl rubber sheeting
– Semi-rigid asbestos asphalt sheeting
– Bitumen/polyethylene sheets
– E.P.D.M. Ethylene propylene Diene Monomer
– Chlorosulphanated rubber (Hypalon)
– PVC Polyvinylchloride
– Neoprene rubber
– Torch-on sheeting consist of layers of polypropylene bitumen modified.
The liquid applied membrane provides a fully bonded, continuous seam-free, homogenous layer with no laps or joins which is a major advantage over sheeting membranes. Some of the liquid membranes available are:
– Mastic asphalt
– Two components polyurethane tar modified
– Two components tar epoxies modified
– Single pack moisture curing polyurethane
– Water based epoxy two part for hydrostatic pressure situations
– Polyester resin two parts reinforced wit fibreglass matt
– Flexible epoxy resin two parts
– Bitumen latex modified single pack
– Acrylic co-polymer water based single part
– Acrylic co-polymer cement modified two components
Properties of waterproofing materials
Full-adhesion to substrate: Waterproofing systems should be fully-adhered to the structural substrate to prevent the lateral migration of water between the waterproofing material and the substrate
Factory-controlled uniform thickness: Waterproofing systems should be manufactured in a factory-controlled environment to ensure a consistent uniform thickness. Variations in thickness may lead to variable performance.
Flexibility over cracks: Waterproofing systems should be flexible enough to withstand typical substrate movements under a wide range of temperature and environmental conditions.
Resistance to high hydrostatic pressure: Waterproofing systems should have the ability to bridge substrate cracks while under high hydrostatic pressure to avoid rupture and leakage.
Positive drainage and protection of the waterproofing: A quality system should include prefabricated drainage composite to both protect the waterproofing from damage and to minimize hydrostatic head pressures.
Ease of application: The waterproofing system should be easy to install at the job site. A simple installation will minimize applicator error. The system should be covered immediately to avoid damage and eliminate job site delays.
Chemical resistance: Waterproofing systems should be resistant to chemicals which may originate from sources within and around the building structure. Chemical exposure may lead to premature deterioration of the waterproofing system.
In-place testability: Waterproofing systems should be tested for water tightness prior to placing the overburden, particularly on horizontal decks. Flood testing is the most common method on horizontal decks. Walls may be visually inspected.
Some of the widely used materials are :
– Rubberized asphalt sheet membranes
– Bentonite Clay
– PVC or high density polyethylene (HDPE)
– Bituminous felts and polymeric bituminous systems
– Lime coba and brickbats
– Concrete Admixtures/Chemical admixtures
– Prefabricated elastic membranes
– Polymer emulsions
– Silicon based emulsions
Rubberized asphalt membrane
The self-adhering rubberized asphalt membrane is the most commonly used waterproofing material. This membrane forms a tough, flexible, thick waterproof material. Its rubber-like properties provide a self-healing character which help ensure waterproofing integrity.
It is an elastomeric sheet membrane designed to waterproof masonry, concrete and wood surfaces, vertically and horizontally, above and below grade.
It is composed of a refined asphalts, synthetic rubber and mineral stabilizers.
It is modified with additives to promote adhesion and improve low temperature flexibility.
Bentonite, technically referred to as sodium bentonite, is a clay formed from decomposed volcanic ash, with a high content of the mineral montmorillonite.
The clay is mined, dried, ground, and sized to provide a finely divided, free-flowing material that will swell to form a waterproof barrier the consistency of heavy grease when in contact with water.
It can absorb large amounts of water, which causes it to swell many times its original volume, forming a waterproof barrier.
The dried, finely ground particles are usually applied as a waterproofing membrane in three ways:
- Bentonite panels
- Sprayed bentonite
- Bentonite sand mixture
Asphalt is a bituminous compound found In many parts of the world and is smooth, hard, brittle, black or brownish-black resinous mineral consisting of a mixture of various hydrocarbons.
Asphalt can be hot / cold-applied to the structures by brush, roller or spray.
These are effective only for situation in which hydrostatic pressure is not factor.
A waterproofing system that will resist hydrostatic pressure consists of alternate layers of hot mopped asphalt over layers of mineral or glass fibre felts in much the same way as laying a built-up roof.
Liquid asphalt has two major advantages over its competitors:
– It is highly elastic, allowing it to bridge cracks and accommodate movement
– It embodies “self-healing” properties, meaning the material will ooze around
and seal a puncture from a nail or sharp object.
Asphalt is most suited to a horizontal application since the hot liquid, mopped onto a vertical surface, can drip, posing a safety hazard.
Mastics are urethanes modified with various polymers to make them flexible.
It is dispensed from a caulking gun with sort of clay-like consistency.
There is a variety of solvent-based mastic waterproofing compounds.
- thick mastic
- semisolid mastic
- spray mastic.
They give waterproofing properties to interior and exterior above-grade and below-grade surfaces.
They are used on metal to prevent corrosion.
These are cold-applied, usually by rolling or troweling
Mastics are easy to apply, but there is evidence that they become brittle and lose their effectiveness more quickly than asphalt.
They are made up of asphalt, bitumen, petroleum, oil and other compounds
PVC or high density polyethylene
This membrane is a composite sheet consisting of PVC / HDPE, adhesive and coating. The membrane can be fixed directly to plaster or brickwork using plastic fixing plugs.
PVC is a high polymer resin and is not affected by aging mildew or corrosion.
It remains flexible at low temperatures and has good abrasion and tear resistance. It is bonded and laps are sealed with a special adhesive.
Some forms of PVC membrane can be formulated to be resistant to gasoline and oil. The seams can be welded with hot air or bonded with an adhesive specified for that purpose. The single-ply sheets, including PVC and high-density polyethylene are less common usage in the industry. As these materials and their application are expensive, especially if there are a lot of details or horizontal-to-vertical transitions.
Bitumen(Asphalt) is a mixed substance made up of organic liquids that are highly sticky, viscous and waterproof.
This felts are generally applied as waterproofing elements for old roofs showing signs of leakage
This is a flexible material.
It is easy to lay and is available in rolls of normal wall width.
It is laid on a layer of cement mortar.
An overlap of 100 mm is provided at the joints and full overlap isprovided at all corners.
The laps may be sealed with bituminous if necessary. The bitumen felt can accommodate slight movement.But it is liable to squeeze out under heavy pressure and it offers little resistance to sliding.
The material is available in rolls and it should be carefully unrolled, especially in cold weather.
Lime and brickbats coba
The aggregate for brick bat coba shall be broken from good and thoroughly well burnt bricks. Brick bat coba shall be in the cement mortar 1:2
Bricks cut along the length having the width equivalent to half brick or full brick are known as brick bats
Brickbat coba will have lot of surface cracks and hence act as a poor waterproofing system.The bricks used in the system are porous and when water enters, these bricks readily absorb and hold large amount of water creating a sort of reservoir above the slab.
Bricks are laid with light weight lime mortar mostly on the flat roof and creating a slope and spreading it for easy draining away of rain water.
This system is popular not because of the waterproofing, but the weather proofing capabilities.
Fine aggregate shall be surkhi, clean free from dust, dirt and foreign matters. Surkhi shall be made from well burnt bricks or brick bats (not over burnt).
Lime shall be freshly burnt and free from ashes and other foreign matters.
Proportion– Concrete shall consist of 1 cu m brick ballast, 0.36 cu m of Surkhi and 0.18 cu m white lime (proportion 100 : 36 : 18 by volume).
Concrete and chemical admixtures
Chemical admixtures are materials in the form of powder or fluids that are added to the concrete to give it certain characteristics not obtainable with plain concrete mixes.
Accelerators speed up the hydration (hardening) of the concrete.
Typical materials used are Calcium chloride, Calcium nitrate and Sodium nitrate.
Accelerating admixtures are especially useful for modifying the properties of concrete in cold weather
Retarders slow the hydration of concrete and are used in large or difficult pours where partial setting before the pour is complete is undesirable. Typical retarders are Sugar, Sucrose, Sodium gluconate, Glucose, Citric acid and Tartaric acid.
Air entertainments add and entertain tiny air bubbles in the concrete, which reduces damage increasing durability.
Defoamers can be used to encourage the air bubble to agglomerate, rise to the surface of the wet concrete and then disperse.
Plasticizers increase the workability of plastic or “fresh” concrete, allowing it be placed more easily, with less consolidating effort.
A typical plasticizer is lignosulfonate. Plasticizers can be used to reduce the water content of a concrete while maintaining workability and are sometimes called water-reducers due to this use.
Admixtures are used for the following use to achieve a higher strength by decreasing the water cement ratio at the same workability as an admixture free mix.
To achieve the same workability by decreasing the cement content so as to reduce the heat of hydration in mass concrete.
To increase the workability so as to ease placing in accessible locations
Water reduction more than 5% but less than 12%
The commonly used admixtures are Ligno-sulphonates and hydrocarbolic acid salts.
Types of water proofing application
Positive side waterproofing
Waterproofing systems should be placed on the same side of the structure as the source of the water.This is known as positive side waterproofing.
Placing the waterproofing on the positive side prevents water from passing through the structure. This protects structural elements from damage due to water infiltration
Negative side waterproofing
Some new structures, and many existing ones, have waterproofing place on the inside or negative side of the structure.
These systems may prevent water intrusion into the interior of a structure; however they allow the damaging effects of water to continue unabated within the structural members.
Blind side waterproofing
In some instances it is impossible, economically or practically, to waterproof the positive side of a structure after the concrete has been poured.
This includes under slabs and against foundation walls cast against soil retaining systems such as timber lagging.
However, waterproofing systems may be installed on the positive side before the concrete structure is poured. This technique is known as blind side waterproofing and requires specially designed systems to provide proper waterproofing.
Water proofing for roofs
The R.C.C. Slab of the terrace is generally done with ordinary concrete without using any admixture to take care of the extra workability required to proper placement and compaction of the concrete through the congested reinforcement.
Sometimes integral waterproofing compounds are used in the concrete. But often they are not used properly or sufficiently. Lime terracing, i.e., Brickbat coba with lime, is done on the R.C.C. slab to serve dual purpose- Weatherproofing and Waterproofing.
Vertical and horizontal joints are treated with the waterproofing mortar, The concrete surface may be treated with a surface applied cement based, crystalline action, hygroscopic waterproofing chemical or polymer based, flexible waterproofing chemical, and then covered with layer of cement mortar admixed with a mortar plasticizer.
Expansion joints and Dynamic cracks shall be filled with flexible and waterproof sealing compound.
For terrace gardens epoxy resins based surface waterproofing material is used .
Waterproofing for basements
These types of system are designed to wholly prevent physical ground water from penetrating the structural walls and floors. Typical products used to provide this protection are liquid applied membranes such as epoxy or bitumous products, self- adhesive sheet systems and cementitious compounds.
This form of waterproofing relies upon the structure itself to form a water resistant shell to resist ground water penetration. Typically these forms are constructed using specially designed concrete incorporating steel reinforcement. Walls and floors are structurally linked with water bars placed at construction joint
The principle of this form of waterproofing is to allow ground water to penetrate the structure so not to allow
hydrostatic pressure build up.
This method manages penetrating water by guiding it to an internal drainage system via a sealed isolating dimpled sheet membrane and directing it to a suitable discharge point outside of the building.
The correct design of the drainage system Is critical to its success.
Waterproofing for footings
The exterior walls of the basement can be coated with a waterproofing substance.
Petroleum-based products have often been used, but newer technologies exist that paint the block with a sealant that is overlaid with a waterproof covering or vapour barrier.
One of the most popular option for Waterproofing existing homes is to install drainage systems around the bottom of the footing and under the concrete floor of the basement.
The drains can be constructed of perforated PVC pipe, encased in a filtering cloth. They are installed on a sand base for cushioning and additional drainage and are covered with a layer of gravel to allow water to drain into the pipe. The cloth prevents debris and rocks from clogging the drainpipe. These hidden interior drain pipes are typically then directed to a sump pump
Waterproofing for kitchens And bathrooms
Under-tile waterproofing of wet areas is essential in order to prevent the buildup of dampness and humidity.
Due to the frequency and intensity of exposure to humid conditions, bathroom and kitchen waterproofing (wet area or wet room waterproofing) is essential to prevent structural, decorative, and even human health related damage.
Left unattended, moisture build up can seriously degrade and destroy primary and secondary facilities
Some of the waterproofing materials used are liquid application of polyurethane materials, absorbent substrate such as fibre cement or water resistant plasterboards
Weatherproofing can be defined as treatment to the surface to prevent it from weather conditions
Building performance is dependent on the ability of the envelope or skin of the building to successfully prevent the ingress of inclement weather, atmospheric contamination such as CO2 emissions, and chemical attack from a variety of sources such as salts from entering the structure. One critical element in maintaining a weatherproof building is the performance of joints in the buildings.
All buildings require joints, and how you seal these joints will be important in determining the overall performance and durability of the structure.
Flashing refers to thin pieces of impervious material installed to prevent the passage of water into a structure from a joint or as part of a weather resistant barrier (WRB) system.
Flashing types are named by their location of uses or shapes:
– Roof flashing :
It is placed around discontinuities or objects which protrude from the roof of a building to deflect water away from seams or joints and in valleys where the runoff is concentrated.
– Wall flashing:
It may be embedded in awall to direct water that has penetrated the wall back outside, or it may be applied in a manner intended to prevent the entry of water into the wall. wall flashing is typically found at interruptions in the wall such as windows and points of structural support.
– Still flasing:
It is a concealed flashing placed under windows or door thresholds to prevent water from entering a wall at those points
– Roof penetration flashing:
They are used to water proof pipes, supports, cables , and all roof protrusions. stainless steel penetration flashings have proven to be the longest lasting and most reliable roof flashing type.
– Chimney flashing:
It is a construction detail used to seal and protect the joints between a buildings roof And chimney from water penetration. Flashing is used at these intersections to Keep rainwater from leaking into the building.
Materials used in Weatherproofing/flashing
Zinc coated: Zinc, an effective galvanizing agent, protects the metal from corroding for a time, but eventually the zinc and then the metal flashing does corrode.
Field handling and bending can crack the zinc film too.
A minimum thickness for this type of flashing should be about 15 mils (0.38 mm). Its durability depends on the thickness of the zinc film. Flashing with thicker zinc coatings lasts longer
Copper: It is moderately priced, a superb moisture barrier, and resists the alkalies in fresh mortar . It also is una ffected by low temperatures and rough handling. Copper flashings are available in 3- ounce sheets. They usually are laminated on both sides with a dense film of polyethylene. This film adds waterproofing and a protective layer that eliminates staining of masonry that could occur if exposed copper were used.
Stainless steel: Its impervious to moisture and resists chemicals well.
Within a masonry wall, stainless steel lasts the life of the building. In most cases, however, stainlessteel flashing must be preformed.
This can create placement problems due to variances in construction tolerances.
They are available in 10 mil (0.25 mm) sheets, although thicker sheets are often used.
They cost less and most of them are tough, flexible, and resilient. masonry.
Some plastic flashings, however, have deteriorated severely when embedded in one type of plastic flashing is a polyester membrane that is 6 mils (0.152 mm) thick. it is highly resistant to corrosion, water permeance, and extreme temperatures. It is a semi-rigid plastic, though, which makes it difficult to bend around corners. The most widely used plastics are polyvinyl chlorides (PVC) (Figure 2). They are homogeneous, waterproof, impermeable sheets that remain flexible and crack-free at -20° F. Because they deteriorate rapidly when exposed to ultraviolet light, however, PVC plastics must be concealed in masonry walls.
They are not attacked by the alkalies in masonry mortars and they are easy to form.
A thickness of at least 20 mils (0.5 mm) should be used. properties.
Combining different materials can produce a moderately priced flashing with good properties. Some of the most common flashing combinations are sheet metals coated with a flexible compound.
One type combines glass fiber or a cotton fabric with a bituminous Compound that is bonded (using heat and pressure) to a 1- to 3-ounce sheet of copper or a combination of copper and lead sheets. This forms a waterproof membrane that resists alkalies and acids.
Another type of flashing consists of textured, waterproofed, creped kraft paper bonded to copper or lead sheet metals with asphalt and reinforced with glass fiber.
These types of combination flashings have life spans similar to those o sheet metal flashings.
A third type of combination flashing is made of a metal foil coated with a polyester film that is reinforced with a glass fiber mesh. The material is waterproof, durable, unaffected by caustic chemicals or low temperatures, and relatively easy to form.
Silicone sealants can be formulated to adhere to all common building facade materials, including concrete, natural stone, brick, aluminum, steel and glass.
Silicone sealants can be formulated to be high-modulus structural adhesives or low-modulus, high-movement weatherseal sealants.
Silicone sealants are inherently resistant to damaging ultraviolet (UV) light from sun, and, when cured, silicone sealants are stable in temperatures from -40C to 150C.
Silicone sealants can also be formulated to have reduced dirt accumulation and be nonstaining on sensitive porous substrates such as marble or granite.
Organic sealants such as polyurethanes and polysulphides are based upon a carbon polymer backbone and do not have the durability of inorganic sealants such as silicone.
Contrary to popular belief, modified silicone (MS) sealants do not actually contain silicone and, therefore, their longterm durability is similar to that of organic sealants.
UV light from the sun can degrade an organic sealant and cause the sealant to harden and lose movement capability after several years of outdoor exposure on a building. This degradation and loss of movement capability can cause premature joint failure.
A wet sealant joint will reduce air infiltration and improve the thermal performance of a facade, provides easy cleaning and maintenance.
Properties of sealants
Sealants serve the purpose of filling the joint to stop water and air infiltration.
The sealant must function to allow the facade elements to move freely, so the sealant must be flexible.
The sealant must also be able to adhere to the joint surfaces as it is being deformed during movement.
Additionally, the sealant must maintain a reasonable level of durability since most buildings are exposed to UV light, heat, cold, moisture and other environmental factors.
Sheeting membranes provide highly trafficable surfaces and have insulating properties.Sheeting membranes in general suffer from poor exposure resistance, temperature stability and little recovery from deformation.
Liquid applied membranes are easy to apply, seamless, semi-flexible or elastrometric, ease of detailing, ease of maintenance and repair, UV resistant and economical.
Coating the surface with cement lime mortar is a time proven and economical method with good insulation properties. But it is non-flexible and also increases the load of the structure.
Mineral slurry with polymer component is an easy method to apply. It retains the breathing capacity of concrete but with moderate flexibility.
Epoxy & polyurethane coating is highly abrasion resistant and resistant to UV radiation and does not add weight to the structure. But this has limited pot–life,not very flexible and stops breathing capacity of concrete.
Elastomeric membrane forming products: It forms seamless membrane, highly flexible, UVresistant, retains breathing capacity of concrete with indirect insulation, but with low abrasion value.
Silicon based impregnators as water repellent, easy to apply and economical, but it has no crack bridging capacity, and does not withstand pressure.
Bituminous based products and modified bitumen are very economical, flexible, with good crack bridging capacity. But it softens under heat and brittle when cold, limited life upon solvent evaporationand other limitation due to its unpleasant black colour.
The awareness and understanding of waterproofing and weatherproofing has grown significantly over the last decade.