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Building
standards require new buildings to incorporate a damp-proof course (often
abbreviated as DPC) at time of construction. This consist of thin strip of
plastic,a course of stone or slate, a layer of bitumen or impermeable RCC band.
Builders neglect this requirement that may lead to many problems.
Types of dampness
There are
five types of dampness found in homes:
• Rising
damp or salt damp found in brick walls and masonry
• Horizontal
penetrating dampness
• Falling
damp
• Poor
drainage
•
Condensation dampness
Causes :
Rising Damp — caused by ground moisture being
absorbed into brick and masonry walls.
Horizontal Penetrating Damp — where rainwater seeps through
defective bricks walls or poor mortar joints.
Falling Damp — is a result of defective roofing
and plumbing equipment, such as leaking gutters, flushes or pipes.
Poor Drainage — built-up garden beds or sloping
ground could direct water under the house resulting in floor dampness.
Condensation—caused by inadequate ventilation or
large variations between the internal and external temperature and humidity
especially in bathrooms.
Rising Dampness
By far the
most common cause of rising dampnessand condensation dampness is inadequate
natural sub-floor ventilation.Lack of ventilation causes a build-up of
humidity and minimal evaporation from the soil and base walls. Both conditions
lead to rising damp through porous bricks walls. Almost all flats have grossly
inadequate provision for sub-floor ventilation and a majority of the minor
rising damp problems can be cured by increasing the ventilation of the
basement, by passive or active method.
Often,
concrete paths or patio floors by the side of the basement have been laid in a
way that will block most of the vents, thus rendering them useless. To ensure
that the entire area is ventilated and there are no dead pockets, it may be
necessary to form openings in the bases of cross walls. Brick and masonry
absorb water, so it must be sealed off from contact with moisture and moisture-bearing
substances like soil. If not, water will rise in the walls causing dampness.
When the dampness evaporates, it creates cold conditions in solid brick and
leaves behind the corrosive salts dissolved in water.
Horizontal Dampness
Basic
horizontal dampness occurs when badly porous brick walls receive direct rain.Horizontal dampness becomes more important to remedy when it appears inside of
the house.The wall can be sealed by the application of a waterproof coating.Painting with silicone admixtures is simplest but will require re-painting
every few years, while bituminous paint lasts longer.Horizontal damp is also
caused by earth bridging damp-proof courses, or obstructions and accumulating
water on exterior walls.Once recognized,these problems are easily remedied by
removing the obstructions. It is best not to repaint the walls for some time to
allow them to dry out after correction.
Falling Dampness
Examine
water and storm water pipes, roofs, and gutters and drain pipes for breakages
and leaks.Excessive dampness which is limited to localized patches on walls
indicates this type of fault. Minor problems can be patched with bituminous
tape or waterproofing adequately.
Poor Drainage
Improve drainage.
From the area near the foundation, drain excess water way via drains and apron
sloping away from the house.
Condensation
Condensation
at home results from damp air, through still air or extreme temperature
fluctuations inside the house.In most cases, condensation will lead to mould
growth and unhealthy living conditions. Water vapour-producing fixtures like
showers, hot water usage in toilets and bath-rooms need to be ventilated,
preferably through exhaust fan, forced to the exterior of the house. In
addition, open windows at night and cut back trees which give the house too
much protection from air and sun.This may also improve sub-floor ventilation
and reduce rising damp. Install insulation to reduce temperature fluctuations.
Overcoming damp-related footing
failures and damp floors:
In some
cases, soil around the house can become so soggy that it fails to support the
foundation loads, causing footing failure and cracking walls. In such cases, it
is very important to quickly implement the drainage and falling damp remedies.In addition structural remedies will also be required. Damp patch problems
sometime occur in houses with concrete slabs.Unfortunately this means the
waterproof course under the slab has holes in it and the ground water has
seeped through the slab into the floor.
First try
the elementary methods of reducing soil moisture, but if unsuccessful you'll
need to remove the floor and waterproof the slab with adequate treatment. Water
Proofing Physical Damp Course:This method has traditionally been regarded as
the most effective (also the costliest) cure for rising damp. It involves
removing a line of bricks close to floor. Then plastic sheet is inserted along
the line and the old mortar is replaced with water proof mortar. Alternatively,
a line is cut in to the bricks themselves with the same waterproofing methods
applied. In all cases, only short sections of the wall can be treated at a time
and the joints must be thoroughly filled and wedged. Otherwise, settlement of the
wall may occur. Each re-mortared section needs to set for around 48 hours
before it can take the weight of the wall again.
Alternatively,
chemical injection under pressure has been used with varying degrees of
success.Pressure injection of alkyl siloxane solution is widely used method.Holes are drilled into bricks at regular intervals.The solution is pumped in
to the holes that permeate the bricks and surrounding mortar creating a broad
band of water repellent work. Pressure injection into mortar course is less
likely to be successful as mortar is weak and often contains many fissures that
will cause the chemical to be lost before the new damp course is formed.
These
methods of waterproofing are very dependent upon site quality control and use
of the correct materials.Many repairs have failed because of lack of proper
care during application.Selecting reputable applicators that are prepared to
give the required guarantee for the work is important for effective
waterproofing.
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