Chapter:Damp Proofing

(i) Rain penetration(ii) Ground moisture rise(iii) Atmosphere moisture(iv) Drainage of site(v) Orientation of Building

1. Sources of Dampness:

A. Geological Causes

(i) Water introduced in structure during construction

(ii) Defective construction

B. Structural Causes

2. Causes of Dampness:Do you see discolored patches on your walls? They are a sure shot sign of dampness. Dampness on walls is usually caused by water leaking from internal drain pipes from the kitchen and bathroom areas. Other causes of dampness include drain pipes running along the sides of your exterior walls, incorrectly placed air conditioner ducts and rainwater running off the side of your walls

Type of dampness  Evidenced by

Rising damp: High moisture readings to external or internal walls

  ‘Tide mark’ type staining of wall decorations at up to 1 meter height

  Salts (called hydroscopic salts) on the wall surface

Penetrating damp: Often isolated to an area of damage to the external fabric

  Worse during or following rainfall

  Internal damage to decorations and finishes

  Localised mould growth , if dampness is persistent.

Condensation: Intermittent – occurs when temperatures are cool.

   

Dampness in Interior Walls of a House

Dampness in a Slab of a Building:

Corrosion of metals used in construction.Plasters get crumbled and softened.Floor, coverings loose adhesion with

the floor.Paints get blistered and bleached.All electrical installations gets

deteriorated.Timber, when come in content with

damp gets rotten.Causes unhygienic conditions for the

occupants of building

3. Effects of Dampness:

Water proofing mixtures.Application of water proof surface treatment.Interposing a water proof membrane.Use of special construction devices.

Grunting.Pressure grouting

4. Prevention of Dampness:

Prevention and treatment Most forms of dampness can be prevented by thoughtful building

design and careful construction. In the UK, well built modern houses include damp proofing in the form of a synthetic damp-proof course (DPC), about 15 cm above ground level, to act as a barrier through which water cannot pass. Slate or "engineering bricks" with a low porosity were often used for the first few courses above ground level, and these can help minimise the problem.

There are many approaches to the treatment of dampness in existing buildings. Key to the selection of an appropriate treatment is a correct diagnosis of the types of dampness affecting a building. Details of possible treatments for specific types of dampness are covered in the sections below.

The cause of the dampness must first be eliminated, by providing better drainage or fixing leaking pipes. BRE Digest 245 describes several methods of treating rising damp, including the use of land-drains and the insertion of physical and chemical DPCs. Then, any affected plaster or mortar must be removed, and the wall treated, before replacing the plaster and repainting.

The End