Most of the leaks occur at window and door openings or at intersections between building components. In some cases, caulks and sealants forestalled leakage at these poorly designed joints for the first few years.
Eventually most caulk joints fail, allowing water to enter. All residential cladding systems are more or less porous to water, particularly during wind-driven rain when high air pressures on the windward side of a building force water to flow towards lower-pressure areas behind the siding.
Water exploits
Under pressure, the water exploits butt joints, lap joints, nail holes and other openings to flow inside (Figure). Even without wind, some water will migrate through tiny gaps to the back of siding through capillary action, the way water is siphoned up a stalk of celery. This is true of brick, wood and stucco, as well as the newest composite materials.
Water penetration of an older home siding
In older construction, water that penetrated the outer cladding had ample opportunity to dry both to the interior and to the exterior as wind washed through the wall cavities, which were kept warm by heat leaking from the building’s interior.
In modern construction, however, with high levels of insulation, continuous air and vapor barriers and low-perm sheathing panels, when water gets in, it is much slower to dry and more likely to cause damage.
This structure relied on diagonal bracing for stiffness rather than an exterior sheathing board. Later an insulation improvement included blowing cellulose into the building walls – which was fine.
But now, water that used to leak into the wall cavity during windy rainy weather soaked the wall interior and was more of a problem.
Luckily cellulose insulation, probably because of the chemistry of its fire-retardant treatment, is rather mold-resistant. But that doesn't necessarily prevent an attack by termites or carpenter ants.
Leaks behind vinyl siding form ice freezing climates. Ice can also show where water leaks or moisture problems are occurring.
Leaks behind vinyl siding form ice freezing
While the exterior finish should be detailed to repel and shed water, a backup system is needed for the times when the primary system fails.
The backup system needs to catch any water that penetrates the cladding and to drain it safely to daylight at the bottom of the wall.
The source of this leakage needs to be found and cured to avoid costly problems such as structural rot, insect damage and even a wall cavity mold contamination issue.
The backup layer in an exterior wall, called a water-resistive barrier by the International Residential Code (IRC), typically consists of properly lapped building paper or plastic house wrap integrated with all flashing to safely drain water away.
It is also called the drainage layer or drainage plane. In this approach, the outer cladding functions as a decorative "rain screen," slowing down wind and water, but it is not expected to be 100% waterproof.
2.25 Roof finishes
Roof is the upper most part of a building which is constructed on structural members and provided with a cover to protect the building and the occupants from atmospheric effects like sun, wind, rain, snow, etc.
Requirements of a Roof :
1.It should give a protective covering against the adverse effects of atmosphere.
2.It should have adequate slope to drain the rain and snow.
3.It should be durable and strong enough to take the external loads.
4.It should provide sufficient insulation against sound.
5.It should meet the different climatic and covering materials available.
6.It should also provide good architectural appearance.
Types of Roofs
Roofs may be grouped under two major categories, viz., sloping or pitched roofs and flat roofs.
1. Sloping or Pitched Roofs
Sloping or pitched roofs are those which have the surfaces with considerable slope for covering the building structure. These roofs are constructed out of wood, steel or combination of both.
These roofs are generally lighter in weight than flat roofs. These roofs are mostly used in regions of heavy rainfall or snow fall.
Different types of roof coverings are in use depending on the type of pitched roof and the availability of material.
2. Flat Roofs or Terrace Roofs
A roof which is nearly flat is known as a flat roof. It is the convention if the slope is less than 10°, it is considered as a flat roof.
As a matter of fact no roof is laid flat. But flat roofs are normally constructed with a slope of 1 in 2 to 1 in 6.
Slope is provided in one or more directions such that the rain water is drained off rapidly. Flat roofs have more advantages compared to disadvantages.
Special care has to be taken with reference to drainage, weather and water proofing. In order to meet, these needs necessary roof finishes have to be adopted.
Drainage of Flat Roofs
It is one of the basic requirements of flat roofs. The rain water should be drained off quickly so as to avoid leakage of roof. In order to achieve this satisfactorily water-tight roof surfaces, adequate slope and drain-outlets have to be provided.
The slopes in flat roofs vary from 1 in 20 to 1 in 40. The rain-water outlets should be evenly spaced round the building. Some possible arrangements of drain-outlets are shown in Fig.
Different arrangements of drain-outlets
Water-proofing of Flat Roofs
Most of the flat roofs now-a-days are of reinforced cement concrete. The flat roof should be made of water-proof by a surface covering. The following methods are employed:
1.Cement mortar finishing
2.Bedding concrete and flooring
3.Mastic asphalt
4.Water-proofing compounds
1. Cement Mortar Finishing
For small size buildings of normal use, the finishing of roof surface is done at the time of laying cement concrete. The flat roof surface is finished with cement mortar of 1 : 4.
2. Bedding Concrete and Flooring
The concrete surface is kept rough over which brickbats lime concrete of 1 : 2 : 4 or brickbats cement concrete of 1 : 8 : 14 is laid for a thickness of about 10 cm.
The bedding concrete is finished with tiles, stone slabs or terrazzo, etc. A convex joint is provided at the junction of parapet wall and the roof.
Water-proofing by bedding concrete in flat roof
3. Mastic Asphalt Finish
A layer of hot mastic asphalt is laid on the roof surface and a jute cloth is spread over this surface.
One more layer of mastic asphalt is laid over the jute cloth such that the jute cloth is sandwiched between two asphalt layers. Then sand is sprinkled over the entire surface of the roof.
A lead sheet is inserted at the junction of the parapet and the roof so as to have a better grip and easy draining.
Water proofing by mastic asphalt in flat roof.
4. Water-proofing Compounds
Commercially available water-proofing compounds are added to cement during construction. These compounds prevent seepage, leakage and dampness caused by capillary absorption of moisture in concrete. Only 2 % of the compound is added.
5. Weather-proof Course for Flat Roofs
Flat roofs are provided with a weather-proof course to sustain the effects of atmospheric agencies. The construction of weather-proof course consists of providing one course of surki-concrete and two courses of flat tiles.
The surki-concrete (broken brick aggregates and lime with no sand) in the mix ratio of 1 : 2 : 5 is laid to a compacted thickness of 75 mm.
The concrete layer is provided with a minimum slope of 1 in 50 directed towards the rain water drains. After curing for six days, two courses of flat tiles (or one course of pressed tile) are laid in a cement mortar 1 : 3 with crude oil.