Concrete Waterproofing is an essential thing because, leakage of water through cracks, expansion joints, or other openings in walls and roofs, or through cracks around windows and doors is a major problem while constructing buildings and structures.
The built structure needs to be strong enough to withstand and protect against floods, snows, groundwater, and rainwater. Leakage should also be prevented from seeping through solid but porous exterior materials. Generally, leakage is prevented by the use of weather stripping around windows and doors, impervious water stops in joints or the calking of cracks and other openings of concrete. However, methods of preventing seepage depend on the types of materials used in the exterior enclosure.
Definitions of Terms Related to Waterproofing (Water Resistance)
Permeability is the quality or state of allowing the passage of water and water vapor from, into, and through pores and interstices, without causing rupture or displacement.
The following terms describe the permeability of materials, coatings, structural elements, and structures follow in decreasing order of permeability:
Pervious or Leaky
The leakages can occur through cracks, crevices, leaks, or holes larger than capillary pores which allow the passage of water and water vapor.
The leakage of a significant amount of water is only possible through openings larger than capillaries but only a few or none of these pores exist. Thus, water-resistant materials cause less damage.
Water- repellent materials do not allow the structures to get wet and water can not stick to the material. So, water can not pass through small cracks or pores. In this type of material, there is a possibility of transmission of water under pressure and somehow it will be permeable to water vapour.
Waterproof materials are the best at preventing leakage of water and water vapor as they are both resistant and repellent against water. These kinds of materials do allow water and vapor to leak whether under pressure or not.
The following terms describe the permeability of a surface coating or a treatment against water penetration. They refer to the permeability of materials, structural members, structures, and whether they have been coated or not.
Followings are the types of basement waterproofing with detail description:
a) Asphalt tanking
Asphalt tanking is the most common method of waterproofing the basement floors. This method of waterproofing is adopted when the subsoil water table level is not very high.
The procedural treatment is:
- The treatment consists of horizontal DPC in the form of an asphaltic layer of 30 mm thick in three coats over the entire area of the basement floor.
- Extend it in the form of vertical DPC 20 mm in three coats on the external faces of the basement walls.
- A 1/2 in the brick thick outer protective wall is constructed.
- The vertical DPC is taken at least 15 cm above the ground level.
- A protective flooring of flat bricks on foundation concrete is provided to protect DPC from damage during the construction of the floor slab.
b) Provision of RCC raft and wall slab
The floor slab and also walls can be constructed in a rigid RCC structure. The constant pumping may not be economically feasible when underground water pressure is severe. In the form of three layers of bituminous felt, horizontal and vertical DPC treatment is done and as in asphalt tanking, at the outer face of the RCC concrete wall slab, the half brick protective wall is constructed.
c) Foundation air drains
The floor as well as the wall receives continuous oozing out of water in various cases. Water seeps out when the basement constructed on soil which is damp and not properly drained receive great hydrostatic pressure. To prevent this, a trench is dug all around up to the foundation level and filled with gravel, coke, or other pervious materials, and a suitable drain pipe with the required slope is constructed. A horizontal and vertical DPC is provided in the foundation concrete as shown in the figure below.
Water proofing at floors
As water proofing of floors is very necessary to prevent any moisture to seep through, a 7.5 cm to 10 cm thick layer of coarse sand is spread over the entire area under flooring after ramming the subsoil, and stone soling can be done alternatively above a low cm thick layer of lean cement concrete. This is done for dry soil without any moisture on the ground floors.
For damp soil, where the water table is near the ground surface, a DPC membrane of mastic asphalt or fibrous asphalt felt is provided above a layer of lean cement concrete. A layer of flat bricks is laid over the DPC to protect from damage during the construction of the floor slab.
Water drainage of roofs
Water drainage differs in case of pitched roof and flat roof:
A pitched or a sloped roof is constructed with a drainage system that is extended for the full length of the roof. This system allows rain and accumulated water to drain out from the outlets. The gutter line or drain pipes are constructed as required for a specific structure.
As for flat roofs, much water can get accumulated so a proper drainage system is required. There are three commonly used methods for flat roof drainage systems.
a) Gutter and downspouts
This method is similar to pitched slopes. In this method, an unnoticeable slope is constructed that guides the water to drain out. To protect the building’s cladding system and the foundation, gutters, and downspouts made up of aluminum, galvanized steel, vinyl, and copper are used which leads the water away.
B) Internal Drains
Internal drains are attached to the descending pipe that goes through the house and is discharged into a sewer. Generally, the roof membrane extends up to the edge of the opening of the drain. The drain which includes a 3inch flange around the top is set into the membrane then stripped in.
They are openings through the parapet wall that allows water to drain to the exterior of the building. Scuppers are generally surrounded by a metal box. For optimal performance, the primary scuppers should be at the level of the roofing membrane and the second one just 2 inches below it that is to be used in case of an emergency when the pathway of water in the first scupper gets blocked.
Permeability of Concrete and Masonry.
Concrete is water-resistant. Concrete structures contain many openings and voids which are very small. These pores are of capillary dimensions and do not allow the leakage of water. Some voids are large but these are very few to none in numbers and are not connected with each other.
Concrete absorbs water when it is not under pressure and the water is drawn into the concrete by the surface tension of the liquid in the wetted capillaries. So, concrete for buildings should be water-resistant, properly cured, dense, and must contain rich concrete containing durable and well-graded aggregate.
The mean focus is to make the balance for water content in the concrete mix as well as incompatible with workability and comfortable placing and handling. The resistance of concrete to the penetration of water can be improved by the incorporation of a water-repellent admixture in the mix during manufacture. (See also Art. 9.9.)
Water-repellent concrete is permeable to water vapor. If the concrete is not made waterproof the use of an integral water repellent and resistor, then the moisture may penetrate from the exposed face to an inner face.
(Note: Water repellents reduce the absorption of water by the concrete but they may not make the concrete impermeable to the penetration of water under pressure.)
Most masonry units also absorb water. Some are highly permeable under pressure. The mortar commonly used in masonry will absorb water which usually contains few openings that allow leakage. Masonry walls may leak at the joints between the mortar and the units. However, except in single-leaf walls of highly pervious units, leakage at the joints results in a poor bond between the masonry unit and mortar.
The above-grade and well-built concrete walls can resist leakage of wind-driven rains. The capillary penetration of such moisture into well-ventilated subgrade structures may also be of minor importance as it is easily evaporated however, long-continued capillary penetration into some deep, confined subgrade interiors frequently result in in excess of relative humidity, a decrease in evaporation rate, and causes dampness. So, with concrete, the rate of capillary penetration through masonry walls is small compared with the possible rate of leakage.
Roof drainage is also very important. If the drainage system is not properly designed and installed, then the water will get ponded and cause various problems. Excessive water accumulation can cause the roof to rot, get moldy, form cracks, and even lead to collapse.
The roofs should be sloped to avoid the accumulation of water along with drainage pipes that take water away from the roof. The primary drainage system should be supplemented by a secondary drainage system at a higher level to prevent ponding on the roof above that level. The drainage system should be prevented from overflow and it should also be cleaned from time to time to prevent clogging of dirt, leaves, and stones.
Drainage for Subgrade Structures
Subgrade structures should be waterproof to prevent any leakage through openings resulting from poor workmanship and reduce the capillary penetration of water into the structure. The drainage of surface and subsurface water using subgrade structures will greatly reduce the time during which the walls and floor of a structure are subjected to water thus preventing leakage, that will produce leakage proof through openings caused by poor workmanship and also capillary penetration of water into the structure is checked by it.
For the process of diversion of surface water special provision is made like grading the ground surface away from the walls and surface runoff water from the roots is lead to a far distance from the building. For a minimum distance of 10 ft (3m ) from the ground, it is better to keep the slope of the surface ground to about ¼ in/ft. Will have to also make them a diversion structure to divert the run-off from the high ground adjacent to the structure.
Drain tile should have a minimum diameter of 6 in and should be laid in gravel or another kind of porous bed at least 6 in below the basement floor. open joints between the tile should be covered with a wire screen or building paper to prevent clogging of the drain with fine material. After that the Gravel is laid above the tile, filling the excavation to an elevation well above the highest of the footing.
Where considerable water may be expected in heavy soil, the gravel fill should be carried up nearly to the ground surface and should extend from the wall a distance of at least 12 in (Fig. below).
Well maintained subsurface drainage of ground water away from basement walls and floors requires a drain of required size, sloped continuously, and, where necessary, carried around corners of the building without breaking continuity. The drain should lead to a storm sewer or to a lower elevation that will not be flooded and permit water to back up in the drain.
Waterproofing for Concrete Floors at Grade
Construction of floors should not be done in low-lying, wet areas with damp soil as it can help moisture transfer to the structure. All organic material and topsoil of poor bearing value should also be removed in the preparation for the subgrade.
The ground should slope away from the floor and the level of the finished floor should be at least 6 in the above grade. Subsurface drains located at the elevation of the wall footings provide protection against ground moisture and possible flooding of the slab from heavy surface runoffs.
In the case of well-drained subgrade, where subsurface drains are used or are unnecessary, we have to insulate the floor slabs of the building by placing a granular fill over the subgrade, in some case we can en-us lightweight aggregate concrete slab cupboard with gravel or stone concrete as a wearing surface. The granular fill used in this case should have a standard specification of:
It should be a minimum thickness of 5 inches (13cm) and should consist of well-graded course slag, gravel, or crossed stone, recommended to of 1-inch minimum size. A layer of 3-, 4-, or 6 in-thick hollow masonry construction units is suitable to gravel fill for insulation and provides a smooth, level bearing surface. It is recommended that for a smooth, level bearing surface it is better to use a layer of 3, 4, or 6 in thick hollow masonry than gravel fill insulation.
The floor slab absorbs the moisture from the ground which can cause floor coverings, such as oil-based paints, linoleum, and asphalt tile, acting as a vapor barrier over he slabs to be damaged.
A two-ply bituminous membrane or other waterproofing material should be placed beneath the slab and over the insulating concrete or granular fill if such floor coverings are used and where a complete barrier against the rise of moisture from the ground is required, (Fig. 7).
It is very necessary to make a smooth level surface for lightweight aggregate concrete by used by troweled or brush. The top of the granular fill should be covered with a grout coating, similarly finished.
(The thickness of grout coat is about 1/2 to 1 in thick, may consist of a 1:3 or a 1:4 mix by volume of OPC and sand. Some 3/8- or 1/2-in maximum-sized coarse aggregate may be added to the grout if desired.) After the top surface of the insulating concrete or grout coating has hardened and dried.
It should be mopped with hot asphalt or coal-tar pitch and covered before cooling with a lapped layer of 15-1b bituminous saturated felt. The first ply of felt then should be mopped by mixing hot bitumen and the second ply of felt laid and mopped on its upper top level.
Water proofing membrane can be used under the floor where there is no possible danger of water reaching the underside of the floor. A single layer of 55-16 smooth-surface asphalt roll roofing which provides a low cost and adequate barrier against the movement of excessive amounts of moisture can also be used. Also, the joints between the sheets should be lapped and sealed with bituminous mastic and proper precautions and great care should be taken to prevent puncturing and damaging the roofing layer.
Waterproofing at Basement Floors
We have to make the floor insulated and make it waterproof by using membrane waterproofing in the case where a basement to be used in drained soil for living rooms or quarters or for the storage of things where the moisture is a destructive agent.
For this, the design and construction of such basement floors are the same as that of the floors on the ground.
The waterproof membrane is not to be used if there are no chances of passage of moisture from the ground into the basement or there is the success of air conditioning as ventilation to control over it.
For the placement (casting) of a concrete slab, it should be maintained a minimum thickness of 4 in (10cm) and not necessary for reinforced, but it is necessary to be laid on a carefully prepared subgrade that is filled with granular fill or other insulation fill over it.
The concrete for this slab should be a minimum compressive strength of 2000 psi () and it may be with an integral water repellent. The 2nd case is when the basement floor is below the water table and can be subjected to hydrostatic upward pressure on the base of the floor. To counteract the uplift, the floor should be designed with heavy self-weight.
The precaution that should be made for the leakage of water into the basement is to use a sealant in the joint between the walls and a floor, otherwise, that leakage water will be accumulated under the slab.
Beveled siding strips are used for space for the joint, which are removed after the concrete is hardened. for the good bond for the joint filler, for decreasing the effects of slab shrinkage on the permeability of the joint then, it is necessary to make the wall surface in a good day condition after the slab is properly cured.
Monolithic Concrete Basement Walls
These walls should have a minimum thickness of 6 in. Where there is a necessity for insulation or as where the basement is desirable for living quarters, then concrete is cast with light weight aggregate that may be prepared by calcining or sintering blast furnace slab, clay, or shale that will fulfill the requirements of ASTM standard c330. The concrete used here should have a minimum compressive strength of 2000 psi.
There are two types of forms in which the concrete used for basement walls can be casted, which are:
- form ties of an internal-disconnecting type
- twisted wire tie
Mostly form ties of an internal-disconnecting type are preferred over twisted wire type.
The procedure for each type of forms is presented below:
- For form ties:
Entrance holes should be sealed with mortar after the forms are removed.
- For twisted wire ties:
They should be cut a minimum distance of 1972 in inside the face of the wall and the holes filled with mortar.
Water repellent admixtures are used to protect the wall against capillary penetration of water in temporary contact with the wall. At the time of concrete casting, the waterproofing material (water repellent) may also be used that may decrease the capillary rise of moisture from the ground into the upper part of walls to the superstructure.
Sometimes the interior face of the wall Is treated with an impervious coating to make the wall resistant to the passage of water vapor (water vapor-proof) from the outside and it also enhances its resistance to capillary penetration of water and is a byproduct like waterproofing surface. The effectiveness and durability of such type of waterproofing are dependent on the smoothness and regularity of the concrete surfaces.
Following are some bituminous coatings used for waterproofing materials to for resistance to moisture penetration:
- Spray- or brush- applied asphalt emulsions.
- Spray- or brush- applied bituminous cutbacks.
- Trowel coatings of the bitumen with an organic solvent applied coat.
- Hot-applied asphalt or coal tar pitch, preceded by application of suitable primer.
The moisture resistance of monolithic concrete can be increased by using cementitious brush applied paints and grouts and trowel coatings along with the addition of a suitable water repellent. These coatings are normally not used in the case of properly drained soil because its result segregation of the aggregate and during casting the wall workmanship is low. On the irregular wall surface types, the bituminous coating is also used with trowel coatings as a waterproofing material.
Unit-Masonry Basement Walls
For waterproofing basement walls, water-resistant basement walls of masonry units are constructed with a serious precaution for leakage and damage due to weathering action like frost, and others are done by selecting suitable durable material.
On the portion of the grade line, frost action is more severe that may cause structural damage and leakage of water.
For the construction of a less severe freezing action component, the masonry unit should have the following properties:
- Spray- or brush- applied asphalt emulsions.
- Spray- or brush- applied bituminous cutbacks.
- Trowel coatings of the bitumen with an organic solvent applied coat.
- Hot-applied asphalt or coal tar pitch, preceded by application of suitable primer.
In the case of exposure conditions, the mortar should be in the following standard: Type S mortar (table…), compressive strength more than 1800 psi according to the requirement of ASTM standard 8270.
For milder freezing exposes and there is a chance of lateral pressure of earth on the walls, the mortar should have a compressive strength of 1000 psi and more.
In some cases, water-stopper is used to protect leakage through an expansion joint in a concrete or masonry foundation wall. Bellows type of water-stoppers is used made with a 16-oz copper sheet, which should be extended of 6 inches in either side of the joint. A joint sealant is made outside of the expansion joint. Water repellent admixture is also used for the prevention of the rise of moisture, by capillarity, from the ground into the superstructure wall.
But the cementation coating could not protect the walls against leakage. If the walls and its coatings are deformed by the differential settlement of the foundation, excessive drying, shrinkage, and thermal cracking.
If the wall is made with hollow masonry units then two trowel coats of mortar having a 1:3 ratio of Portland cement and sand are applied. One trowel coat may suffice on the outside of all brick and of brick-faced walls. Take care of the wall surface and top of the wall footing should be cleansed dirt and soil and harmful material and the masonry should be sufficiently wetted with water.
While still damp, the surface ought to be lined with a skinny scrubbed-on coating of hydraulic cement tempered to the consistency of thick cream. Before this ready surface has dried, an-in-thick trowel-applied coating of mortar ought to be placed on the wall and over the highest of the footing; a fillet of mortar is also placed at the juncture of the wall and footing.
Where a second coat of mortar is to be applied, as, on hollow masonry units, the primary coat ought to be damaged to supply a rough bonding surface. The second coat ought to be applied a minimum of one day once the primary, and therefore the coatings ought to be cured and unbroken damp by wetting for a minimum of three days.
A water-resistant admixture within the mortar used for the second or end coat can cut back the speed of capillary penetration of water through the walls. If a hydrocarbon coating isn’t to be used, the mortar coating ought to be unbroken damp till the backfill is placed.
Thin, impervious coatings may be applied to the plaster if resistance to penetration of water vapor is desired. The plaster should be dry and clean before the impervious coating is applied over the surfaces of the wall and the top of the footing.
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Impervious membranes are a type of waterproof enclosure type membrane which may check against the entrance of water under hydrostatic pressure and water vapor. In this type of membrane, a suitable water-resistant membrane is laid continuously in the walls and floor of a basement. Great care should be kept during building construction operations and it should also be laid with great care by experienced workers.
It usually consists of three or more alternate layers of hot, mopped-on asphalt or coal-tar pitch and plies of treated glass fabric, or bituminous saturated cotton or woven burlap fabric. The number of mop pings is one more than the number of plies.
Alternatives are cold-applied bituminous systems, liquid-applied membranes, and sheet-applied membranes, similar to those used for roofing. In the installation, manufacturers’ recommendations should be carefully followed.
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Bituminous saturated cotton fabric supreme material than bituminous saturated felt because it is stronger and is more extensible properties but is more expensive and more difficult to lay. At least one or two of the plies in a membrane should be of saturated cotton fabric to provide strength, ductility, and extensibility to the membrane.
Where vibration, temperature changes, and other conditions conducive to displacement and volume changes in the basement are to be expected, the relative number of fabric plies may be increased.
The minimum weight of bituminous saturated felt utilized in a membrane should be 13 lb per 100 ft^2. The minimum weight of bituminous saturated woven cotton fabric should be 10 oz/yd^2.
The membrane is held rigidly in place for better result but, it is advisable to apply a suitable primer over the surfaces before applying the membrane and to help in the application of the primary mopped-on coat of hot asphalt or coal-tar pitch.
The following current ASTM standards should be required for Materials utilized in the hot-applied system:
- Creosote primer for coal-tar pitch-D43
- Primer for asphalt-D41
- Coal-tar pitch—D450, Type II
- Asphalt-D449, Type A
- Cotton fabric, bituminous saturated—D173
- Woven burlap fabric, bituminous saturated—D1327
- Treated glass fabric-D1668
- Coal-tar saturated felt-D227
- Asphalt saturated organic felt-D226
As the hydrostatic head to which the membrane is to be subjected is increased then it most be necessary to increase the number of plies of saturated felt or fabric. Five plies is the maximum For normally in building construction five pile is enough, but 10 or more plies have been suitable for pressure heads of 35 ft or greater.
The amount of primer to be used could also be about 1 gal per 100 ft^2. The amount of bitumen per mopping should be at least 41/2 gal per 100 ft^2. The thickness of the first and last mopping is usually slightly greater than the thickness of the moppings between the plies.
The surfaces should be smooth, dry, and at a temperature above freezing, then only we can apply the membrane. Air temperature should be not less than 50°F. The temperature of coal-tar pitch should be less than 300°F and asphalt, 350°F.
If the concrete doesn’t absorb the priming coat, the application of the membrane should be stopped and the bitumen already applied to damp surfaces should be removed. The membrane should be constructed ply by ply. In any membrane, there should be a lap of the top or final ply over the first, initial Ply of at least 2 in. End laps should be staggered at least 24 in, and the laps between succeeding rolls should be at least 12 in.
A suitable concrete base is made before application of membrane. The membrane should be started at the outside face of the wall and extend over the wall footing. It should cover the floor completely making it moisture tight. The loose ends of felt and fabric must be protected by fastening them to a temporary vertical wood form about 2 ft high, placed just outside the wall face. After laying the floor membrane it should be protected by concrete.
The installed membrane should be protected against damage and held in position for protection against the abrasion of the membrane. In this type the membrane may be applied to the exterior face of the wall after its construction. A proper stiffness protective facing is plied for the protection against lateral force.
The completed membrane should be covered with as-in-the thick layer of mortar to protect it from damage during construction of the main wall. Wall membranes should be applied from the bottom portion of the wall.
The rate of moisture penetration through capillaries in above-grade walls is low however, such walls should not permit leakage Caulking compound is commonly used as a facing for the joints. There is a maintenance problem in calking compounds in bad weather condition when use as joint facing.
The control of movement in the vertical joints between panels depends upon the panel dimensions and the seasonal fluctuation in temperature and, for concrete, the amount of moisture in the concrete. An interlocking water-resistant joint is recommended for the panel construction.
In general, the greater the number of brick leaves, or wythes, in a wall, the more water-resistant the wall. The Walls of hollow masonry units are generally highly permeable, and faced with brick. The resistance of the brick facing to prevent leakage of wind-driven rain. For exterior concrete masonry walls without facings of brick, protection against leakage may be obtained by facing the walls with a cementitious coating of paint, stucco, or shotcrete.
For the wall of rough-textured units, a Portland cement-sand grout provides a highly water-resistant coating. We can use both either white or gray cement. Factory-made Portland-cement paints containing a minimum of 65%, and preferably 80%, Portland cement may also be used as a base coat on concrete masonry.
The application of the paint should conform to the requirements of ACT 515.1R. The paints, stuccos, and shotcrete should be applied to dampened surfaces. Shotcrete should conform with the requirements of ACI 506R.
Cavity walls, particularly brick-faced cavity walls, maybe made highly resistant to leakage through the wall facing. However, as usually constructed, facings are highly permeable and the leakage is trapped in the cavity and diverted to the outside of the wall through conveniently located weep holes.
The weep holes may be formed by the use of sash-cord head joints or 8-1 diameter rubber tubing, withdrawn after the wall is completed. Flashings should preferably be a hot-rolled copper sheet of 10-oz minimum weight. They should be lapped at the ends and sealed either by solder or with bituminous plastic cement.
The incidence of shrinkage cracking is the use of the dry block. When applied for the wall, the block should have a low moisture condition, preferably one in the state of equilibrium with the driest condition to which the wall will be exposed. The block should also have low potential shrinkage.
Formation of large shrinkage cracks may be controlled by the use of steel reinforcement in the horizontal joints of the masonry and above and below wall openings of brick, ordinarily cannot be stopped by the use of an inexpensive surface treatment or coating that will not alter the appearance of the wall. This type of protective device has a drawback of low service life or fail to stop all leakage.
To stop leakage we can apply both organic and cementitious pigmented coating materials properly on continuous coating over the exposed face of the wall. Many of the organic pigmented coatings are vapor barriers and are therefore unsuitable for use on the outside, “cold” face of most buildings. If vapor barriers are used on the cold face of the wall, it’s advisable to use perfect vapor barrier materials on the warm face.
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As given below the Coatings for masonry are divided into four groups:
- colorless coating materials
- cementitious coatings
- pigmented organic coatings
- bituminous coatings.
Colorless Coating Materials:
It is found that colorless “waterproofing” is often could stop leakage of wind-driven rain towards permeable masonry walls. Solutions of oils, pain wax, sodium silicate, chlorinated rubber, silicone resins, and salts of fatty acids have been applied to highly permeable test walls and have been tested at the National Institute of Standards and Technology under exposure conditions simulating a wind-driven rain.
Most of these solutions contained not more than 10% of solid matter. The rate of leakage is reduced by this type of treatment but is not perfect for the leakage through the walls.
According to research data, the protection against the wind-driven rain is not stopped by colorless coating materials used to permeable walls of bricks or concrete masonry.
For waterproofing to seal the larger openings especially at the joints, solutions of oils and waxes used to seal the pores exposed in the faces of mortar joints and masonry units that play as more or fewer vapor barriers.
The best material is Silicon water repellent solutions that may reduce leakage by the walls to a greater extent.
After an exposure period of 2 or 3 hours, the rate of leakage gradually increased as the water repellency of the wall face diminished. Coatings of the water-repellent. breather type, such as silicone and “soap Solutions” may be of value in reducing the absorption of moisture into the wall surface.
The water repellents so ought to be applied solely to walls having waterproof joints. what is more, the application of a colorless material makes the treated face of the masonry water repellent and will stop the correct bonding of a building material coating that might well be accustomed to stop discharge?
Coatings of Portland-cement paints, grouts, and stuccos and pneumatically applied mortars are highly water-resistant. They are the best among all of the other types of surface coating for use on waterproofing (water resistance) coatings on above-grade concrete masonry units.
It is used to make water proof for the exposed faces of brick masonry walls that have not been built to be water-resistant. The cementitious coatings permit the passage of water vapor but absorb moisture and are like the breather type. The addition of water repellents to these coatings does not greatly affect their water resistance but does reduce the soiling of the surface from the absorption of dirt-laden water.
If more than one coating is applied, as in a two-coat paint or stucco facing job, the repellent is preferably added only to the finish coat, thus avoiding the difficulty of bonding a cementitious coating to water repellent surface. The technique used in applying cementitious coatings is highly important. The backing should be thoroughly dampened.
It is to be kept in mind that paints scrapped with the help of stiff fiber brushes and the coating should be properly cured by moisture (wetting). The grounds are highly durable and will be long last up to 10 years for waterproofing even in doors sure on when first applied on the wall.
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Pigmented Organic Coatings:
The pigmented aqua coatings consist of textured coatings, mastic coatings, conventional paints, and aqueous dispersions. The thick-textured and mastic coatings are usually spray-applied but may be applied by trowel. Applied as a continuous coating, without pinholes. The pigmented organic coatings are highly water-resistant.
On the smooth backing, it is most effective to use. It is hard to level the surface and when we can use paintbrushes or spray by conventional methods to rough textured walls It is not sufficient for continuous waterproofing coating free from holes.
The pigmented organic coatings are highly decorative but may not be better water-resistant, economical, or durable as the cementitious coatings.
Bituminous cutbacks, emulsions, and plastic cement are usually vapor barriers and are sometimes applied as “damp proofers” on the inside faces of masonry walls. We can use plaster over the coating and the stability of plaster on it is by mechanical nature.
Many research shows that it is not the best method to use bituminous coatings to the inside faces highly permeable masonry walls, not plastered, that may cause blisters and may leakage of the water through the coating.
It is recommended that such type of coating is not suitable for waterproofing to prevent the leakage of the wind-driven rain unless it makes a rigid with self-sustaining backing or is incorporated in the masonry.
The main drawback is even we can use walls with resistance to wind-driven but are treated on their inner faces with a bituminous coating, the water may condense on the warm side of the coating, and the plaster is damaged. But, if there are no chances of condensation occurs on the warm side, then the bituminous will be the best for a vapour barrier in furred walls.
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