Causes, Prevention And Treatment Of Damp On Building

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LITERATURE REVIEW

This chapter addresses the literature review to guide the study. It is organised under the following sub-headings:

Damp

Causes of damp

Identification/symptoms of damp

Measures for preventing damp

Treatment of damp in building component

Damp

To be more realistic, damp in building cannot be avoided due to the climatic condition, but it can be prevented on a building to a minimal level which can serve as an antidote to the causes and effects of damp in a building. Damp in building can occur naturally when the foundation of a building is not well treated with the appropriate material which may lead to rising damp. Moreover some of the home facilities and equipments in a building can also cause damp-equipment such as the air condition, refrigerator and microwave contributes to more action of damp known as condensation. This occurrence happens not due to the lack of knowledge of the builder or the occupants about damp, but by not applying the necessary treatment which can normalize the effects of damp in the building.

Olusanya (2004) ascertain that damp in building can be caused by bad eaves or inadequate gutters or cracked roofing tiles, broken pointing, improper wall thickness, poor construction and inadequate protection.

More so, when considering the causes, prevention and treatment of damp we should know that damp occur in different means which are condensation, rain penetration, rising damp and humidity.

Melvin and Gordon (1998) consider damp as underground water reaching the foot of a wall therefore tend to rise in the walling materials and will continue to do so due to rise in capillary action to varying degrees of intensity. This penetration of ground is commonly known as rising damp.

Burkinshaw and Parrett (2003) explain damp more comprehensively as moisture that travels upwards through the pore structure, or via small fissures or cracks or as water vapour against the force of gravity, typically up a wall through a floor from a source below the ground.

Troutman (2004) define dampness as the normal upward transfer of moisture in a porous material due to capillary action.

Causes of Damp in Building

Damp (structural)-Wikipedia (2014) the free encyclopaedia suggested that damp is caused by the following:

Condensation

Rain penetration

Rising damp

Humidity

Condensation

Barry (2010) opines that Condensation forms on and within cold materials-the warm internal air can hold a considerable amount of moisture, which is generated by people, gas burners and kettles, if the air becomes colder it has to give up the water it contains and as the warm air hit the cold air water will be deposited in them. Condensation comes in different from water vapour within the building. Condensation is the drops of water that form on a cold surface when warm water vapour become cool. Common source of condensation may include cooking, bathing, and dish ace, sometimes inside the walls called interstitial condensation.

However, building with poorly insulated walls is very prone to this problem. It often causes damages similar to damp in a building and often appears in similar places. This is because it occurs in the “dead air” pocket that accumulates in both horizontal and vertical corner (i.e. out of circulating air patterns). Damp condenses on the interior of the buildings due to specific interactions between the roof and walls.

Identification of Condensation

If it is suspected that the problem is condensation, then a room should be sealed with a dehumidifier left running for the recommended time and then further instruments made. If the dampness has disappeared, then condensation is very likely the problem.

Alternatively humidistat cards or data logger (measuring air, air temperature, and surface temperature) can be used as tools for diagnosing a condensation problem.

Treatment for Condensation

Typical remedy for condensation as recommended by Hutton Tim (2000) includes:

increasing background heat

ventilation of cold surfaces

Reducing moisture generation (e.g. by avoiding the drying of clothes indoors).

Rain Penetration

Rain penetration is also known as penetrating damp, is a common form of dampness in a buildings. It can occur through walls, roofs or through opening (e.g. windows reveals).

Water will often penetrate the outer envelope of a building and appear inside which can lead to this common defect which includes:

Roof defects such as faulty flashing, cracked or missing slates or crack pointing porous bricks or stones.

Missing or defective mastic around windows and doors.

Blocked weep holes

Missing or defective trays in cavity walls

Symptoms of Penetrating Damp

The most common visual symptom of rain penetration is damp patches or internal walls. Often causing paints to flake or wall paper to peel. However, damp masonry caused by penetrating damp can also result in a wide range other symptoms including:

Reduce thermal resistance of damp masonry, Causing heat loss and condensation.

Moss and mold growth

Frost damage

Rotting of embedded timber.

Disfiguring carbonate deposit

Rain penetration is often associated with single skin walls but can also occur through cavity wall e.g. by tracking across wall ties. The most common source of indoor moisture at the base of the walls in buildings is from defective ground and surface drainage. This is due to rising ground levels and failure of ground drainage systems. These defects are common nationwide.

The Traditional Measures for Preventing Penetrating Damp

A wide range of traditional measures are available to deal with the problem of rain penetration through walls as seen in damp (structural) Wikipedia (2014). These include:

Cladding (a protective covering of a hard material)

External renders

Weatherproof paints and coatings

Tide or slate hanging

Timber boarding

Rising Damp

Hutton Tim (2000) sees rising damp as the common term for the slow upward movement of water in the lower section of walls and other ground-supported structures by capillary action. Rising damp is widely misdiagnosed in existing buildings, based on the incorrect interpretation of visual evidence and the readings of moisture meters.

Christopher and William (2007) view rising damp as an important causes of wetness in building which leads to decay and deterioration in standing stones, monument and at archaeological site. Because of a highly successful sales campaign for over 30 years by specialist remedial contractors installing injected chemicals ‘chemical damp proof course’, this misdiagnosed of rising damp has also become synonymous with a diagnosis of a lack of an ‘injected chemical damp-proof course’.

An entry in British medical journal from (1872) describe the phenomenon of rising damp as follows: even if the rising damp be arrested by what is technically called an impervious damp-roof course, it will be frequently found that this is built in the wall too near the ground line, so that the heavy rain be splatters the ground also becomes elevated, and this damp course is soon lost sight.

Attempt has been made to remedy this evil of porous bricks by the substitution of the hard brisk of Staffordshire, and then it may be often noticed that wet has only struck sailor-like Thomas Worthington described in his essay, “the dwelling of the poor and weekly wage earners in and around the towns”. It should be borne in mind that damp in walls absorb much more heat than dry ones and that they are frequent agents in causing rheumatism, kidney diseases and colds.

Prevention for Rising Damp

Rising damp from the ground as explain by Arora and Bindra (2010) can be prevented most by simple means, six inches of a good Portland cement concrete never less than nine inches thick should underlie all walls. A damp course should disconnect the whole of the foundation from the superstructure. This preventive may consist of a double layer of thick slates bedded in cement or of patent perforated stone-ware blocks or of three-quarters of an inch of best asphalt.

How rising damp occur: according to jurin’s law the maximum height of rise is inversely proportional to the capillary radius

Jurin’s law H= 2ycos Ө

Rpg

Where:

y=surface tension, Ө=contact angle, R=capillary angle, p=liquid density and g=gravity.

Taking a typical pore radius for building materials of a 1 jurin’s law would have give the maximum rise about 15m, however, due to the effects of the evaporation, in practice the rise would be considerably lower.

In many cases damp is caused by “bridging” of a damp-proof course that is otherwise working effectively, for example a flower bed next to an affected wall result in soil being peeled up against the wall above the level of the d.p.c. level.

Treatment of Rising Damp

Where a rising problem is caused by a lack of damp-proof course (common in buildings over approximately 100 years old) or by a failed damp-proof course (comparatively rare) there are a wide range of possible solutions available as elucidated by Don prowler (2011). These include:

Replacement of physical damp-proof course.

Injection of a liquid or cream chemical damp-proof course (d.p.c injection)

Porous tubes/other evaporative method e.g. Shriver

Land drainage

Electrical-osmotic system

Plastering.

Replacement physical damp proof course: a physical damp proof course made from plastic can be installed in an existing building by cutting into short section of the damp proof course material, this method can provide an extremely effective barrier to rising damp, but is not widely used as it requires experienced contractors to carry out if structural movement is to be avoided and takes considerably longer to install than other types of rising damp treatment. The cost is also higher than other types of rising damp treatment.

Injection of a liquid or cream chemical damp proof course (dpc injection): injection of a liquid or a cream into bricks or mortals is the most common method of preventing/treating a rising damp. Liquid-injection products were introduced in 1950s and were typically installed using funnels (gravity feed method) or pressure injection pumps. The effectiveness of liquid injection damp proofing products is dependent on the types of formulation and the skill of installer in practice injection time tends to be lower than those required to provide a damp proof course optimum effectiveness.

Porous tube: porous tube is installed along a mortar course in theory these are supposed to encourage evaporation and reduce the rise of the damp. No independent test carried out by the Building Research Establishment suggests that they are not effective at controlling rising damp.

Land drainage: it has been suggested that improving drainage is around walls affected by rising damp can help to reduced the height of rise by reducing the amount of water available to be absorbed into the capillaries of the wall typically a trench would be excavated around the affected wall into which a porous pipe would be laid. The trench would then be backfilled with a porous material such as a single-sized aggregate forming a French drain.

Electrical osmotic system: this attempt to control rising damp through the phenomenon of electron osmosis whilst there is evidence to suggest that the systems can be useful in moving salts in walls, there is little in the way of independent data to demonstrate effectiveness in treating rising damp.

Plastering: plastering will often be carried out as part of a rising damp treatment. Where plaster has become severely damaged by ground salt there is a little argument about the need to plaster. However there is a considerable debate about:

The extent of plastering required

The use of hard sand cement: cement renders to plastering as part of arising damp treatment.

Moreover, the function of the new plaster is to prevent hygroscopic salts that might be present in the wall from migrating through to his surface, while still allowing the walls to dry.

Humidity

Humidity by Trotman and peter (1925) is the amount of water vapour in the air and when excessive moisture is present in the home this allows dampness and the growth of bacterial, mold and fungi which can be harmful to our health. Our body respond to humidity by sweating which cool us down. But when we have humidity in home to some level it causes us to feel uncomfortable and to have other problems like allergic reaction of the organisation thrive in wet cold conditions. And because of this we need to get rid of house humidity or at least control it. Not all humidity is bad however; we need some moisture in the air to prevent problems of dry skin irritation, dehydration, breathing difficulties, static electricity and cracking of wood. For example, the problem with high humidity indoor is that it causes:

Condensation leading to damp and mold and ideal environment for house pests, such as cloths moths, fleas, cockroaches, woodlice and dust mites.

Allergic reaction to house pest, such as asthma and breathing difficulties in those with respiratory problems.

Thermal discomfort where we generally feel hot, bothered and sweaty and often lose sleep in such conditions.

Destruction of soft furnishings, furniture and building fabrics.

Musty odour.

Prevention for Humidity

Julie and Andrea (2011) supports that there are strategies to prevent water infiltration due to humidity into structures, as well as way to treat human occupancy practices regarding humidity. Vapour retarders are materials that can be used to restrain uncontrolled airflow and water vapour into an indoor air space. Vapour retarders are used to reduced/decrease the rate and amount of water vapour diffusion through ceiling, walls, and floors caused by humidity.

Treatment of Humidity

Humidity can be treated by installing vapour retarder into flexible materials and its coatings which can be done through brushes or trowels. It should also be noted that moisture source, such as hot tubs or indoor swimming pool should be covered by airtight lids when not in use, thus humidity levels stay low in the indoor environment.

According to Peter Brett damp can arise from the main external source: rain penetration, rising damp and condensation. In addition, leaking plumbing, roof leakages, heating system and spillage of water in use are also significance causes of damp.

Roof Leakages

Another major causes of damp in building is caused by bad material used in the roof covering, poor workmanship or inexperienced workmanship which can later result leakage of the roof.

Peter Brett (2004) deduce that roof-loose or missing tiles or slates including the hip and ridge will allow rain water to run down rafters, causing damp patches on the ceiling and tops of walls. He also specify, that the major area of roof leakage is around the chimney stack and other roof-to-wall junctions which may be due to cracked chimney pots, cracked or deteriorating flaunchings (the slopping mortar into which the slope are set),or corroded or pitted metal flashings.

Prevention for Roof Leakage

Arora and Bindra (2010) specify that roof leakage on the wall can be prevented by ensuring that all cornices and string courses should be provided. Window sills, coping of plinth and string course should be sloped on top and throated on the underside to throw the rain water away from the walls.

Treatment of Roof Leakage

In case of flat roofs as suggested by Arora and Bindra (2010), the rain water enters either through the defective parapet wall, or cracked roofing tiles or broken pointing, etc. The waterproofing treatment given to flat roofs in their various forms are: Lime concrete terracing, lime concrete terracing with flat tiles, and mud phuska terracing with tiles (used in India)

1st method of waterproofing, i.e., lime concrete terracing has been recommended for 'Hot and Humid Regions' in India, viz., Kolkata, Mumbai, Chennai, etc. The process consists of laying the lime concrete at adequate slope; application of hot prime coat of bitumen over dried lime concrete and finally laying sheet of bitumen over the primed surface.

2nd method of waterproofing, i.e., limes concrete terracing with flat tiles has also been recommended for hot and humid regions mentioned above, where the roof is to be used for sleeping or such other purposes. In such cases, the roof is strengthened by covering the lime concrete with" two courses of brick tiles laid in cement mortar to withstand the wear and tear effects due to traffic.

Lack of Drainage

Barry (2010) opines that drainage should be laid in straight lines wherever possible to encourage the free flow of discharge water by gravity and with gentle curve only where straight runs are not practicable. So as well lack of drainage can leads to damp in a building due to the irregular movement of foul water from the building which can settle at an unwanted component of the building. Hence there should be presence of drainage either separate or combine in a building to avoid damp.

Prevention of Lack of Drainage

In order to prevent the lack of drainage in a building Ralf F Burkinshaw (2009) opines that there must be the general construction of drainage in the society by the government which can serve as the mains in which other drainage from the building can be connected with. It is also mandatory for building designer to enlighten their client about adequate uses of drainage in building for them not to misuse it when it’s even available.

Treatment of lack of Drainage

Martellata (2006) denotes that improving drainage around walls affected by rising damp can help to reduced the height of rise by reducing the amount of water available to be absorbed into the capillaries of the wall typically a trench would be excavated around the affected wall into which a porous pipe would be laid. The trench would then be backfilled with a porous material such as a single-sized aggregate forming a French drain. Such a system would obviously suitable for the treatment of damp outside wall and it would be impracticable where other buildings are close or where a building has a shallow footings.

Techniques and Methods of Damp Prevention in Building

Arora and Bindra (2010) reveals that the following precautions should be taken to prevent the dampness in buildings, before applying the various techniques and methods described later:

1. The site should be located on a high ground and well drained soil to safeguard against foundation dampness. It should be ensured that the water level is at least 3 metres below the surface of ground or lowest point even in the wet season. For better drainage, the ground surface surrounding the building should also slope away from the house or structure.

2. All the exposed walls should be of sufficient thickness to safeguard against rain penetration. If walls are of bricks, they should be made of at least 30 cm thickness.

3. Bricks of superior quality, which are free from defects such as cracks, flaws, lump of lime stones, etc., should be used; they should not absorb water more than 1/8 of their own weight when soaked in water for 24 hours.

4. Good quality cement mortar {1 cement : 3 sand) should be used to produce a definite pattern and perfect bond in building units throughout the construction work. This is essential to prevent the formation of cavities and occurrence of differential settlement, due to inadequate bonding of units.

5. Cornices and string courses should be provided. Window sills, coping of plinth and string courses, should be sloped on top and throated on the underside to throw the rain water away from the walls.

6. All the exposed surfaces like tops of walls, compound walls, etc. should be covered with waterproofing cement plaster (i.e., 1 cement: 3 sand + waterproofing compound).

7. Hollow walls (i.e., cavity walls) are more reliable than solid walls in preventing dampness and hence the cavity wall construction should be adopted wherever possible.

Treatment of Damp in Building Component

The use of damp-proofing courses (D.P.C.), for the treatment of buildings, against dampness, can be grouped into the following categories:

1. Treatment of foundations' dampness from adjacent ground.

2. Treatment of foundations on bad (poor) soils.

3. Treatment of basements,

4. Treatment of floors,

5. Treatment of walls,

6. Treatment of flat roofs, parapets and copings.

1. Treatment of Foundations' Dampness from Adjacent Ground: In case the moisture rises up the walls through the foundations where water is percolating from the adjacent ground, this may be treated by providing air drains and damp-proof course or by D.P.C. alone. Sub-soil drainage may also be provided to solve this problem. An air drain is a narrow dry space (20 to 30 cm width) which is provided on the outer face of the wall below the ground level. It is formed by a thin outer wall resting on the base slab of foundation and carried little above the ground level (usually by 15 cm) to prevent water entering the drain. Openings with gratings are provided at regular spacing for the passage of air. The top of air drain is covered either with R.C.C. slab or stone slab and due provisions for examination and clearing this drain is made.

2. Treatment of Foundations on Bad (Poor) Soil: Where the foundations of basements are not properly drained (in dry or peat soil) and hence subjected to great hydrostatic pressure, then in such cases the structure should be disconnected from the face of the ground excavation and trench made all around for width of about 30cm taken down to a point as low as under side of the concrete footings. This becomes essential, because the more provision of continuous D.P.C, may not give satisfactory results. The bed of the trench should be provided with a good slope at each end and the trench filled with coke, gravel, or stone, graded with fines to fill the voids. Moreover, in such cases the basement is relieved of hydrostatic pressure by suitably draining the sub-soil water. Sub-soil water may be by providing open jointed land drain at the bottom of trench and also drainage-pipes below the concrete base. The open jointed pipes or drains are given a bed slope so that the water is discharged in an outlet outside the building from where the collected water is allowed to flow away in some natural drain.

The gravel bed helps to accumulate the sub-soil water by seepage and percolate the same in the pipes.

3. Treatment of Basements: to ensure the dryness, the whole of the structure below ground level should be provided with a continuous membrane of asphalt (i.e., D.P.C.) either mastic asphalt or bituminous felt supported on the inside. This is achieved by spreading a layer of an impervious material (i.e., D.P.C.) over the whole area of the floor and continuing the same (i.e., Horizontal D.P.C.) through the external walls extending vertically up, forming a sort of water- proof tank. The details of asphalt tanking or waterproof or D.P.C. tank and sequence of operations in providing D.P.C. for basements in buildings, have been shown in but the following points require due consideration in asphalt tanking.

(i) D.P.C. for basements of building should be provided in dry season when Hub-soil water is at its lowest level.

(ii) D.P.C. is provided on the outside of walls and under floors of basements and underground structures, in such a way that the latter may provide support necessary to withstand such water pressure as may be exerted on the outer faces of the structures.

(iii) Horizontal D.P.C. is laid continuous and extended vertically up through the walls. This vertical D.P.C. should either be taken above the ground for a minimum distance of 15 cm or may end in a horizontal D.P.C. if necessary.

(iv) An adequate dewatering arrangement for pumping out sub-soil water should be installed in order to keep water level below the operating level or working level.

(v) Suitable shuttering should be provided to prevent the excavation from collapsing.

(vi) D.P.C is laid over the entire base slab of concrete including the projection of 15 cm.

(vii) A protective flooring of brick flat on cement concrete (1 : 3 : 6) is laid to protect D.P.C. from damage during the construction of floor. The structural walls and floors are then constructed to withstand the anticipated water pressure.

(viii) Sufficient care should be exercised to ensure a perfect bond between the D.P.C. on the base slab and that on the outside of walls.

(ix) The gap between thin protective brick wall (half-brick) and structural wall should be grouted so as to ensure that no air is trapped between the D.P.C. and the walls.

4. Treatment of Floors: For dry locations, generally, a filling of 7.5cm to 15 cm of dry coarse sand under the floor masonry is specified. A hardcore filling of stones with smaller stones to fill in voids is also suitable. The filling should be well rammed but not unduly consolidated. It is observed that a thin layer of cinders and coal tar under a tiled floor acts as a good D.P.C. to prevent the moisture as well as efflorescence.

In case, there is possibility of moisture penetrating the floor, it will be necessary to lay a waterproofing membrane of mastic asphalt or fibrous asphalt felt, before a concrete floor is laid. It happens, because porous concrete attracts moisture from the wet soil and is also aided by capillary action. Even a dense concrete waterproofing compound is not found a perfect barrier to moisture. Hence, generally, over dry concrete bedding, a priming coat of hot liquid asphalt is first given and men mastic asphalt is applied in two coats. In case, there is possibility of the floor being subjected, to excessive uplift pressures due to soil and water table characteristics, then concrete floor should be reinforced. The D.P.C. of mastic asphalt over the slab should be covered with a concrete wearing coat.

5. Treatment of Walls: In case of basements, the external face of the wall is well grouted with a water proofed cement plaster. This forms the base for the asphalt layer (i.e., vertical D.P.C.) which is continued from the basement floor and extended vertically up covering the whole area of the external wall face. This vertical D.P.C. is further protected by a thin skin wall or protective wall.

The horizontal D.P.C. in external walls is generally provided at least 15 cm above the ground level. It is further essential to provide a vertical D.P.C. between the floor level and the D.P.C. level on the inside of external walls. In internal walls, the d.p.c. is provided in level with the upper surface of the concrete floor. The continuity of D.P.C. between the internal and external walls is attained by way of cement concrete blocks on bituminised bricks.

If the D.P.C. is to be provided in an existing wall, then a cut about 15 cm or more above the ground is made at the corner of the wall: loose bricks on materials above the cut are removed; and a damp-proof membrane of bituminous felt is inserted inside the cut. This process of cutting the slots and inserting the damp-proof membrane is continued, till the entire length of wall is completed. The removed materials like bricks are re-laid and the wall surface is plastered or pointed. D.P.C. details in cavity walls have already been. In this, a horizontal D.P.C. is laid at least 15 cm above the ground, A layer of lead sheet, copper sheet or asphalt felt is brought down from the inner wall to the head of the floor or window, to protect the openings. To protect the window sills, D.P.C. of bituminous felt or lend sheet can be inserted between the inner wall covering and the sill. Generally, a porous external treatment of plaster, having proportions (1 cement: 1 lime: 6 sand) to the walls is recommended to safeguard against dampness,

6. Treatment of Flat Roofs, Parapets and Copings: In case of flat roofs, the rain water enters either through the defective parapet wall, or cracked roofing tiles or broken pointing, etc. The waterproofing treatment given to flat roofs in their various forms are: Lime concrete terracing, lime concrete terracing with flat tiles, and mud phuska terracing with tiles (used in India)

Summary of Reviewed Literature

This section of the literature review tends to summarizes damp as follows:

Ralf F Burkinshaw (2009) describes damp as a level on the external envelop of a building which are liable to moisture effects caused by pooling or splashing or impinging of (usually) rain water at the junction of a horizontal surface to the vertical wall surface-being most common at the wall base. Melvin and Gordon (1998) consider damp as underground water reaching the foot of a wall therefore tend to rise in the walling materials and will continue to do so due to rise in capillary action to varying degrees of intensity.

In Julie and Andrea (2011): the major causes of damp are: condensation, rain penetration, rising damp and humidity.

Peter Brett (2004) added that damp can arise from the main external source: rain penetration, rising damp and condensation. In addition, leaking plumbing, roof leakages, lack of drainage, heating system and spillage of water in use are also significance causes of damp.

Julie and Andrea (2011) enumerate prevention of rain penetration as cladding (a protective covering of a hard material), external renders, weatherproof paints and coatings, tide or slate hanging, timber boarding

Damp treatment in building can be provided depending on the causes of the damp and they are:

Typical treatment for condensation including increasing background heat and ventilation of cold surfaces and reducing moisture generation,

Rain penetration-cladding (a protective covering of a hard material), external renders, weatherproof paints and coatings, tide or slate hanging,

Rising damp-replacement of physical damp-proof course, injection of a liquid or cream chemical dam-proof course (d p c injection), porous tubes/other evaporative method e.g. shriver, land drainage, electrical-osmotic system, plastering,

Humidity-Humidity can be treated by installing vapour retarder into flexible materials and its coatings which can be done through brushes or trowels.

The use of damp-proofing (D.P.C.), for the treatment dampness in building component according to Arora and Brinda (2010) can be grouped into the following categories: Treatment of foundations' dampness from adjacent ground, Treatment of foundations on bad (poor) soils, Treatment of basements, Treatment of floors, Treatment of walls, and Treatment of flat roofs, parapets and copings.

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