damp proofing course archna

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DAMP-PROOFING COURSE By ARCHANA SREELEKSHMI ASWATHY y

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Page 1: Damp proofing course archna

DAMP-PROOFING

COURSE

ByARCHANASREELEKSHMIASWATHY

y

Page 2: Damp proofing course archna

Dampness a common problem in buildings.

It refers to access and penetration of moisture content into buildings through its walls, floors, roof etc.

It is important to take measures to prevent dampness.

Such measures is called damp proofing.

Water proofing is a treatment of the surface or structure in a building to prevent leakage.

WHAT IS DAMP PROOFING?

Page 3: Damp proofing course archna

Moisture from ground:-The materials used for the foundation and floors absorb moisture from the soil and it rises up the surface of the building,

Splashing of rain:-When rain splashes on external walls dampness may enter the interior.

Exposed top wall:-dampness enters from the top if the tops of parapet walls are not given sufficient damp proofing course.

Condensation: dampness is caused due to condensation of atmospheric moisture, deposited on walls and ceilings.

Construction defects:- Improper planning, lack of proper slope in roof, defective pipe fittings, improperly sealed construction joints are constructive defects.

CAUSES OF DAMPNESS :-

Page 4: Damp proofing course archna

Ugly patches on walls and ceilings. Plaster softens and crumbles. Materials used for wall decorations are damaged. Stones ,bricks and tiles disintegrate due to efflorescence. Floor finish may be damaged Woodworks decays due to dry rot. Metal components of building corrodes. Electrical fittings are damaged, Dampness leads to breeding of mosquitoes, growth of termites and germs carrying diseases such as tuberculosis, it also aggravates asthma.

Effects of dampness:-

Page 5: Damp proofing course archna

Requirements of ideal materials for damp proofing:-

They should be :-

impervious. Durable Capable of bearing the load Dimensionally stable Flexible Free from sulphates, chlorides and

nitrates. inexpensive

Materials for damp proofing

Page 6: Damp proofing course archna

Hot bitumen :-hot bitumen,3mm thick may be applied on bedding of mortar or concrete.

Mastic asphalt:-semi rigid material obtained by heating asphalt with sand and mineral fillers. It is laid on mortar or concrete bed.

Bituminous felt:-flexible material available in rolls. It is laid on flat mortar finished surfaces.

Metal sheets:-sheets of lead, copper and aluminum may be used membranes in damp proofing. Lead is the most ideally suited material.

Materials used for damping:-

Page 7: Damp proofing course archna

Combination of sheets and felts:-economical and drable damp proofing sheet is obtained by sandwiching a lead sheet and bituminous felt.

plastic sheets:-a relatively cheap method of damp proofing is by laying 0.5-1.0mm thick plastic sheets made of black polythene. This is not a permanent method.

Bricks:-quality bricks absorbing water less than 4.5% of their weight may be used for damp proofing. These bricks are laid in 2-4 courses in cement mortar.

Mortar:-cement mortar in the ratio 1:3 is used for bedding layers over damp proofing course. It may be mixed with slaked lime to improve its workability.

Cement concrete course:-a cement concrete course of proportion 1:2:4 and thickness 75-150mm is laid on masonry at plinth level.

Page 8: Damp proofing course archna

General principles to be followed in damp proofing are:-

Mortar bed prepared to receive damp-proof course should be leveled.

The horizontal damp proofing course should cover the full width of wall excluding rendering.

If sheets or mastic asphalt are used, the gap should not be less than 100mm at any point.

At joints and corners. Damp proof course should be continuous.

Damp proofing course should not be kept exposed on the wall surface.

At vertical and horizontal junctions, damp proof courses should be continuous and a cement mortar fillet of about 75mm should cover joints.

Principles of damp proofing:-

Page 9: Damp proofing course archna

Different types of treatments are used for preventing dampness in diff parts of the building:-

Foundations:-this is method of protecting foundations of outer walls. An air drain is constructed parallel to the

wall. The drain is covered with RCC slab, and gratings are provided at regular intervals, horizontal and vertical damp proof courses are also provided.

METHODS OF DAMP PROOFING:-

Page 10: Damp proofing course archna

Treatment for floors:- if there is no damp soil, a layer of coarse sand,75-100mm

thick is provided over entire area under the flooring. Then 1:4:8 concrete of 100mm thickness is laid. This layer serves as DPC. the usual flooring is provided over this,

If soil is wet, a membrane DPC is provided over the floor area, over

which a layer of flat bricks is laid. The usual flooring is then provided.

Page 11: Damp proofing course archna

Treatment for walls:

the plinth level should preferably be 450mm above ground level.DPC should be provided over a concrete bed of thickness 100-200mm.the top of the parapet should be provided with capping over the DPC. the wall also needs DPC at the edge of the roof slab.

Page 12: Damp proofing course archna

Providing foundation drains and DPC:- to release hydrostatic pressure,trenches are

made all around the building and filled with gravels etc. such trenches may also be required in buildings if the water table is at a higher level. The trenches lead the water to a catch drain.Horizontal and

vertical DPCs are provided in

the walls and foundation concrete.

Methods of waterproofing basement:-

Page 13: Damp proofing course archna

Providing RCC raft and wall slab:-

if the water pressure is high, providing a drainage system will not solve the problem effectively. In such cases the floor slab and wall may be prepared right through the RCC structure and DPC is applied on it.

Page 14: Damp proofing course archna

Asphalt tanking:- also known as membrane

waterproofing.

Construction of horizontal layers :a leveled course of mass concrete is laid for the flooring area ,over which a 30 mm thick DPC in form of asphaltic layer is provided a protective layer of cement screed, concrete or a layer of brick work is

laid over the asphaltic layer, after which the flooring is prepared.

Page 15: Damp proofing course archna

construction of vertical face:-

A vertical DPC is provided on the external face of the wall. The DPC consist of an asphalt layer of about 20mm built in three coats. This is then protected with a wall of ½ brick thickness.

Page 16: Damp proofing course archna

Lime concrete terracing:- The RCC roof is cleaned

thoroughly and a bitumen primer is applied ,3 coats of hot blown asphalt is then applied over which a specially prepared lime concrete bed of 100mmthickness is provided. The surface of bedding is covered with flat tiles. a convex corner

joint is made at the junction with the parapet wall.

Waterproofing of flat roofs:-

Page 17: Damp proofing course archna

Membrane water proofing:-

water proofing membrane may be prepared with mastic asphalt or plastic sheet. It is provided in a number of layers from 2-7.in this method a layer of hot mastic asphalt is applied on the clean roof surface. This is covered by jute cloth and another layer of mastic asphalt is laid.

In case of plastic membranes, hot coating is applied with blown bitumen between each layer. The top is usually finished with a course of flat tiles.

At the junction is properly sealed with the parapet. The membrane should extend up to parapet or lead sheets should be inserted.

Page 18: Damp proofing course archna

Water proofing compounds may be grouped to 2:-

Waterproofing admixtures:-these admixtures are in powder or liquid form. About 2% of powders are mixed while making cement mortar. when the finishing coat of mortar is provided, these compounds seal the pores in the slab and make

them watertight.

Using waterproofing compounds:-

Page 19: Damp proofing course archna

Waterproofing membrane system:-these materials are available in the form of paints, they may epoxy or elastomeric and may be applied to roof slabs with rollers ,brush or spray. a minimum of 2 coats are applied to get desired waterproofing.

Page 20: Damp proofing course archna

Sloped RCC roofs are provided with tiles for purpose of weather proofing. It is preferable to use flat tiles fixed to roof.

If Mangalore tiles are used care should be taken. continuous motor bands should not be provided as reapers because in case rainwater entering through broken tiles stagnates on the mortar bands, leakage will occur. Hence mortar bands supporting Mangalore tiles should be discontinuous. before laying the tiles, the possible leakage points should be checked and identified.

Water proofing of sloped concrete roofs:-

Page 21: Damp proofing course archna

THANK YOU

BY

ARCHANA

ASWATHY

SREELEKSHMI