Leakage Prevention in Building structure

   Leaking terraces, leaking toilets, damp walls, wet patches underside the slabs, pealing of plaster and paints, fungus growth is very common in buildings now-a-days. If a close look is taken, one will come to know that the cause of all these defects is either rain water or domestic water used by the occupants seeping through the structure. These defects do not render the building totally useless for occupation. However, one will agree that such defects are very leak so profusely that occupants cannot find inch of a place to sit or lie down during monsoon. There are few examples where occupants sometimes have to use umbrella or polythene sheet while using the toilet. These toilet blocks leak through out the day whether the toilet above is being used or otherwise. Damp spots on the walls results in pealing off plaster decolouration and fungus growth.

Fungal Growth on wall 

Slab Under W.C. Leakage

Wet spot on slab without any water source

Terrace Slab

Leakages through terrace slabs generally occur due to following reasons:

    Concrete slab is not cast properly and provided with appropriate slope.

    It is a truth that the best way to fight with water is to give way. By only this means, one can win over this strong element of nature. if slab is not laid to proper slope, water stagnates over the slab and in due course it finds way into the crevices and seeps into the structure. At the time of laying concrete, if proper care is not taken, it can results honeycombed concrete. It further leads to voids in the structure and subsequently serves as storage reservoirs and path of seepage gets established.

Concrete being heterogeneous material, it cannot be watertight. This belief is half truth. Even though concrete is heterogeneous material, if proper care is taken, it can become watertight. If terrace slab is cast with the proper measures by-

    a)  controlling the mix properly, 

    b) controlling water cement ratio and slump, 

    c) vibrating and placing the concrete, 

    d) correctly maintaining the top profile the slab, 

any of the defects highlighted in colour as mentioned above can be avoided.

 It is observed that generally masonry parapet walls are provided over flat terrace slab most of the buildings.

 It is experienced that the terraces are hardly used and it remains as a show piece only. So only for the sake of show, concrete slab for terrace are laid without slope. Masonry parapets further aggravate the problem. 

Parapet wall on terrace

Terrace slab in combination with parapet wall compounds large quantity of water. If no proper drains are thought of during construction, it results in ponding water over the terrace and the structure In subjected to leaking. There are some buildings which leak even after the stoppage of monsoon for substantial period. This leakage is due to the stagnation of water over the terrace and moisture held in the slab. Terraces are also used for keeping overhead water tanks. The leakages through these overhead water tanks also cause stagnation of water on the terrace which give constant trouble.

Incorrect drain pipe placement without any slope

Drain pipe slightly below slab level, brick IPS flooring overlapping pipe

 If proper layout for store water is prepared at the time of planning only, some of these problems can be avoided.

 It is experienced that in case of combination of terrace slab and parapet type construction, no proper thought is given to make parapet walls damp proof and non porous. The R.C.C. column extensions for future expansion are many times corrected with lean concrete such as 1 3:6, 1:4:8.

No doubt, this may facilitate easy breaking of concrete at latter stage. However, for the present stage, it creates a source of constant trouble. Parapet walls are lap constructed without proper care as they are not load bearing and contain lot of voids. No. proper care is also taken to keep away the water falling on the top of parapet. If we look back in the past, it is observed that proper designs of parapet were used to be adopted. The coping on top of parapet was provided with drill. This coping prevented water passing continuously over the parapet walls. Now-a-days simple plastering is done on the top of parapet walls which generally becomes a great source of dampness in the buildings. There is also lack of attention while making the junction of slabs and parapet wall. In the past, lead flushing was used to be provided at this junction. This lost flushing used to protect this Joint and used to avoid dampness and leakages in the walls.

 In terrace slab and parapet wall type construction, terrace slab is cast flush with the outer face of the structure. Water falling in this slab finds is way through the Junction and through cracks between the masonry wall and slab. Inspite of proper design of the slab, some structural deflection is going to take place in the slab. 

This deflection and subsequent rotation of the slab at the ends create a hair crack on the outer face of the will below the slab. This crack leads to water seepage in the structure. Many of us do not think that this is also a major source of dampness. If this defect is to be contracted, best way is to provide a projected slab at least 25 cm to 30 cm. all round The buildings. This will ensure that water falls clear off the structure and the rotation crack is well protected by the projection.

    In combination of terrace slab parapet wall type construction, storm water is required to be taken down through water pipe and down take pipes. In present day frame structures, such down take pipes are taken along the columns for obvious reasons. Many a times these columns are cast upto top of parapet either for future expansion or for architectural appearance. However, those columns pose a problem of outlet arrangement. Generally, 90 bend and a 45 'y' type bend are required to be introduced. Such bends are difficult to make them water tight and subsequently during maintenance they are difficult to maintain. Because of two curvatures they cannot be cleaned properly, and also cannot be clearly seen whether they are blocked or otherwise. a correct method is to provide a down take pipe which goes straight in the slab without bends. This can only be achieved by projecting the slab outside the face of the building and taking down take pipes in such fashion. It is also noticed many a times that water spouts are not provided at the level at which they should have been provided. It is noticed that the invert level of the water spouts is many times higher by few inches than the finished terrace slab. Thus, water spout do not function sometimes and the water below the invert level remain stagnated on the terrace. If these levels are properly adjusted and the invert level is sunk down sufficiently, it will ensure full drainage of the terrace.

 In load bearing structures of old type, slab is not provided with full bearing and it rests on half bearing only. In such cases one more source of the leakage is joint, between vertical face of the slab & the masonry. If this is not properly attended to this Joint gives trouble. Best way to deal with such cases is to provide proper water proof terrace parapet and lead flushing Junction.

Incorrect

   Leakages through cracks, near chajjas

Correct

In case of buildings provided with corridor slabs at different levels than the terrace slab or pitched roof, no sufficient slope is provided to the verandah slab for the obvious reasons of appearance. If at all, proper slope cannot be provided to such slab, atlast properly laid out coba needs to be provided on top of these slab so that water does not remain stagnant on it. Stagnated water find a way through the slab as well as through the interior wall junctions. Best way to avoid such situation is either to provide proper slope to verandah slab or to provide well laid water proof course with proper slopes away from the wall having proper rounding at the junction of the internal wall and verandah slab. It is a good practice to provide a small inverted beam bend at the junction of internal wall and the verandah slab. This inverted bend raises the increase of water to a great extent and many problams can be avoided by this type of construction.

Incorrect

Correct

Leakages through water closet (W.C.)

Leakages through W.C. are mainly through the following

1) Junction of W.C. pan and the trap. 

2) Junction of the W.C. trap and the outlet pipe going through the wall.

3) Junction of lead flushing and the W.C. pan. 

4) Joints in the floor slab, floor finish and the pan, floor finish and the walls

5) Joint between the wall piece and  the right angle bend introduced in the wall 

6) Through the 'y' Junction.

    Toilet slab.

If we know the anatomy of the plumbing connection in the W.C. block, we will see that there are lot of theumatic joints in this construction. It will also make us aware of the importance of right workmanship in this field. It is common observation that many times this job is left to the entire whim of the plumber and no Engineer cares for in toilet block. It may be due to rush at the end of the work or even due to the apathy of an engineering about this Job.

It is generally thought unimportant and non engineering aspect of the building. However, if we look from the angle of the user, it is very important from his point of view. If proper care and scientific approach is taken during construction and installation of the W.C. blocks, much of the troubles can be avoided. Now-a-days sunken slab and sloping slabs are generally provided for the W.C. blocks. However, no care about the proper concreting such as mix and water cement ratio and slump is taken. This sunken slab concrete becomes porous than the other slabs in the building because of its crooked shape and difficult access, no proper thought is given to this portion of the concrete. Now a-days it is practice amongst the engineers to provide Inverted beam it the outer face of the building to accommodate the sunken or sloping W.C. slab. 

Plan View

If such inverted bean is really required to be provided, it should have sufficient depth to accommodate the pan properly. 

Section For R.C.C. structures

Section for load bearing structures

Generally depth equal to 60 cm essential. However, many designers proved this bean having depth of 40 to 45 cm. which is inadequate to Accommodate pan and the trap.

No proper openings are kept in this inverted beam. At the time of plumbing the beams are broken open and holes are provided in this beam to take out outlet pipes. If proper planning is made before hand, PVC pipe opening can be kept at such location and pipe can conveniently be accommodated there. Best way to avoid this situation is to provide conventional beam at the appropriate location below the sunken slab. This will solve many problems rising out of this. It is also observed that in many buildings, particularly ownership buildings, where the sloping slab is provided without any side wall etc i.e. other sides of the sloping side and these walls are subsequently constructed with half brick wall. These partitions below the floor are constant source of leakages and such type of construction shall be avoided. 

Incorrect slab sloping

Correct slab slope and drain arrangements

After concreting the sloping slab carefully, the sloping slab should invariably given water proofing treatment as an extra safety. It is also desirable to provide an outlet having a small diameter G.I. Pipes or PVC pipe for any contingency that may arise at latter stage.

    Flushing Connection 

Once the water proofing is done, laying of pans, trap and other features should be taken in hand, Flushing pipe taken from the flushing tank generally shall be of lead, due to pilferage contractors hesitate to provide lead pipes. Therefore, there is now-a-days a practice of providing G.I. pipes in place of lead pipe for the flushing pipes. This is very undesirable. It may be noticed that the flushing pipe is to be provided with about 4 to 5 bends to accommodate the profile of the W.C. Such pipe can absolutely not to be fixed without compromising its leak proofness. It is also difficult to make joints of this pipe with the W.C. pan and what actually done is just to keep both ends together and a plaster mortar all around. Slight dislocation even at the time of handling creates a permanent source of leakage in the W.C. In such situation use of PVC pipe is far better than the G.I. pipe. For one reason it can be laid to any desired shape and secondly the joint with W.C. pan is easier with PVC pipe than G.I. pipe. 

    Pan and Trap  

Major defect in W.C. through the Junction of pan and the trap. At this, junction is about 40 to 45 cm. below the floor and is in-accessible. Unless proper care is taken, it is very difficult to make this joint properly.

    Trap and Outlet Pipe

 Similarly, Junction between the trap and the pipe leading to the outside face of the building is also difficult. Unless proper care is taken, it cannot be made properly water tight. Pipe leading to the outside face of building has to pass, through wall and it has to have junction with bends or 'Y' junction pipe at the outer face. This face is also difficult to approach and hence no proper jointing is done at t is location and this causes a constant source of leakages.

    Flooring

Junctions between the tile and the walls, tile and the pan also cause leakage in the W.C. looking to the quantum of water used for ablusion, leakage from this source is not much significant.

To avoid the leakage to W.C. proper care at the time of laying W.C. and plumbing connection needs to be taken. There should not be any compromise on this regards. Proper water proofing to the sloping slab, its sides and taking care of the Junctions of various plumbing fixtures will avoid leakages in the W.C. blocks. As an additional safety of pressure release, pipe as stated above will be helpful in many locations. This pressure release pipe will release the trapped water out side the building. Similarly, plumbing is not done in a scientific way in many of the buildings. The joints are required to be provided with cement mortar. This cement mortar should be just moist and in a form of a moist powder only. Such mortar should be well caulked and joints with the help of wooden wedge and after proper caulking of the joints they should be cured properly. Simple way of curing will be to put a gunny bag place around the joint and keep the gunny bag wet of some days. This will ensure strength of the joint and water proofness.

Bath Room 

Leakages in the bath rooms generally take place through

1) flooring and 'Nahani trap'. 

2) Joint between 'Nahani trap' and the pipe leading to the outside face of the building.

3) Pipe leading to the outside face of the building and the downtake pipe leading to 'y' Junction.

4) Through the junction of flooring and the walls and the junction of the flooring tile etc.

    Floor Slab.

Floor slab of the bath room should be sunk to accommodate the pipes etc. Generally, slab should be sunk about 15 to 20 cm. for bath room. Further sinking 20 cm. x 20 cm. should preferably made for accommodating the Nahani trap. This will ensure proper draining of the toilet block. After careful laying the sunken slab with proper mix and proper water cement ratio and slump, the slab should be provided with water proof brick bat coba. At the time of laying the coba, Nahani trap should be inserted in its final position and then only the flooring should be laid. If dado or skirting is provided for the bath room, water proof plaster should be done before such rendering. Junction between dado and floor should be attended properly. Flooring of the W.C. should be atleast (25 mm to 40 mm) below the general floor level so that water does not get spread on the general floor when bath room is being used.

    Nahani Trap 

The Nahani trap should be placed in the recess provided in the sunken slab. The waste water should be directed towards the nahani trap by providing proper slope to the flooring. level of the nahani trap should be so adjusted that it is at the lowest possible location. Joints between nahani trap and the flooring tiles should be properly sealed with rich dry mortar and well caulked.

    Nahani Trap and Wall Piece. 

This junction is difficult to make water tight unless special care is taken. Joints between the trap and Wall piece should be filled with rich dry mortar and should be caulked with wooden wedges. There are some cases noticed at later stage wherein wall pieces were simply not provided and only ends of the Nahani trap and ends of the right angle bend were facing each other and gaping hole in the masonry was supposed to act as pipe to convey the waste water from trap to the outlet. This is only due to the unscrupulous tendency of the plumber and apathy of the supervising staff. Now-a-days 45 m. long Nahani traps are available in the market, if they are used, some problem can be reduced.

    Downtake Pipes. 

Junctions of downtake pipes, wall piece and bend pipe should be provided with similar water tight joints. It is also observed that while making junctions, no proper sequence is followed by the plumbers. Plumbing should preferably be done from one end and finishing towards the other end. It is observed that generally work is started from both ends and finished at the middle. In order to avoid problems of A.C. pipe Junctions, PVC pipes can be used, which are easier to Join and make water tight. They are lighter to install also.

    Access During Maintenance. 

As no access is provided to the downtake pipes. it becomes difficult to reach the trouble spot while doing repairs. In absence of such access, no expert inspection of the trouble spot is carried out and the work is left to the unskilled labour who carries out the repairs per his limited knowledge. If some platform or in built system is provided permanently to the structure during construction, only expert inspection will be frequent and further troubles can be avoided.

    Sunk and Wash Basin. 

Leakages through wash basin are not much serious but are irritating. Basins leak through the junction of wash basin and the trap, wash basin and the outlet pipe and through Nahani trap. Initially, the joint between wash basin and the bottle trap are easily accessible and can be repaired without much difficulty. However, many a times, wrong material is used for this and it causes difficulty while repairing: The outlet pipe should be lead pipe or PVC pipe. G.I. pipe should not be directly fixed to the wash hand basins. Due to circled situation near basin it is not possible to make proper joint with G.I. at this location. Similarly, water connection to the wash basin should not be given directly by joining basin tap to G.I. pipe. The connection should be through rubber connecting pipes or PVC between G.I. pipe and basin tap usual precautions for Nahani trap connection are essential.

Kitchen sinks look through the following joints :

1) Joints between side walls of the sink and the floor slab. 

2) Joint between outlet and the floor slab, 

3) Spill out of the waste down outlet to Nahani trap etc.

Leakages through side wall and floor slab junction occur due to nonhomogeneous Joint between the different materials like concrete and brick work . This work is also carried out in most hurried fashion taken up at the last stage only. It is better to provide proper water proofing to the bottom and sides with sufficient rounding at the corners. It is desirable to provide full one piece sink instead of sink of heterogeneous materials. Precast sinks are available in the market which are better and cheaper than the subsequent trouble. Joint between sink and the outlet can easily be made water tight if proper couplings are used and proper care is taken to put packing and tightening the coupling. Length of the outlet pipe should be sufficient to reach the Nahani trap. many a times this piece is very short and water splashes on the floor and create silty conditions.

Canopy and Chajja. 

In order to keep away the rain water protecting the opening, canopies and chajjas are provided, but the very sources create a damp nuisance in the structure if not properly executed. 

Leakages in the chajjas are through following sources 

a. Junction between the masonry and the top of the chajja. 

b. sides of chajja. 

c. Leakages through chains slab only.

If proper care is taken at the time of casting of chajja and proper slope is provided to the top surface leakage from this source can be avoided.

While finishing the chajja, many a times the edges are unnecessarily raised and this creates a barrier which contain water and even this small quantity of water can create dampness and fungus growth in the chajjas.

Due to deflection and temperature variation, a crack gets developed between the masonry and outer face of the chajja slab. This is generally very near to the top of the slab. Moisture finds, access through those cracks and create damp patches on the wall around the lintels. If thick lintel or inverted bend is provided with sufficient rounding near this junction this problem can be permanently solved.

If no dip moulding is provided at the overhanging edges of the chajja, water travels drop by drop on the underside of the chajja and creates a damp condition in the opening. Similarly many a times vertical pardies are provided at the edges. The edges instead of turning down, are turned up. This creates a water tank at the top of chajja and is a constant source of damp ness even after the provision of the water spouts. Best way to avoid this is to provide silts to such portion and provide dropping (turned down) vertical pardis.

Many times, width of the chajja along the wall is cast equal to the width of opening or even less. This all leads to the water dropping on the opening and causes dampness in the structure.

Leakage through Expansion Joints in terrace slab

Expansion joints are generally provided in buildings longer than 45 meters. The general pattern of expansion joint consist of a set of twin columns, twin beams and a gap is provided between these twin beams/ columns filled up by bituminous filler sheet.

The provision of expansion joint at the terrace level possess some difficulties. Normally we provide twin beams projecting above the slab level. The first portion (say left side) is cast first along with the aluminum or copper plate embedded for sufficient length in the beam projecting above slab. The right side is then cast with bituminous sheet in between the two portions. The whole joint is covered by lead plate so that water does not find any way into the joint.

This is, however, best with some problems, The lead covers are costly are likely to be stolen. Instead of lead, if G.I. covers are used, they would tend to corrode and thus maintenance problem would arise in very short time after the construction.

Current Practice

Therefore, a more fungible and workable pattern is suggested. In this, the left side is cast first, with the beam projecting above the slab and cast along with aluminum plate embedded in it. The top of this beam in kept sufficiently sloping (say 4 cm. in a 23 cm. width of beam). Bituminous sheet are fixed between the left and right portion and the right portion is cast as a beam projecting above the slab with a concrete cap over the left side beam A nosing is made as shown with a drip so that water cannot find its way into the joint. By providing a concrete cover, the problem of maintenance of lead or G.I. sheets is got rid off. Also the possibility for water finding its path into the Joint is minimized since the joint does not remain vertical at the top, but is an inclined joint sloping away.

Proposed Structural arrangement

Concealed fittings

Concealed fittings may create problems if drilling work required to be done, sometimes holes in the pipes are done unknowingly, if pipe is running full then leakage is easily detected at same time and remedial measures can be undertaken but if pipe is empty while drilling such holes in go unnoticed and it may create leakage problem.

Accidentally drilled in Water Pipe