ROOF AND ROOF COVERING

ROOF AND ROOF COVERING 

  ROOF :-

A roof is part of a building envelope, both the covering on the uppermost part of a building or shelter which provides protection from weather, notably rain, but also heat, wind and sunlight; and the framing or structure which supports the covering

In Simple words “Roof is what, Covers both Material & Human Being”

    QUALITIES OF ROOF:-

-  Must be weather resistant to rain, snow, wind and sun.

-  The durability should be equal to or in excess of those materials used in the remainder of the building.

-  Should have good thermal insulation properties.

-  Should require a minimum of maintenance.

-  Should be constructed in such a way as to retain structural stability when dead and imposed loads are applied to it

Truss & Its Component:-

- Heel - The point on the truss where the top and bottom chords intersect

- Slope - The vertical rise in inches for every 12 inches of horizontal run.

- Panel Length - The horizontal distance between the centerlines of two consecutive panel points along the top or bottom chord.

- Peak - The point on the truss where the sloped chords meet.

- Top Chord - Horizontal distance between the centerlines of two consecutive panel points along the top or bottom chord.

- Continuous Lateral Brace - Members installed at right angles to a chord or web member of a truss to provide stability to the truss. All lateral braces must be stabilized.

- Overall Height - Vertical distance between bearing and the uppermost point of the peak.

- Wedge - The triangular piece of lumber inserted between the top and bottom chords, usually to allow the truss to cantilever.

- Bottom Chord - The incline or horizontal member that establishes the bottom of a truss, usually carrying combined tension and bending stress.

- Splice - The location at which two chord members are joined together to form a single member. It may occur at a panel point or between panel points.

- Panel Point - Also called a joint, it's the location on a truss where the web members and top or bottom chords intersect and are connected by metal connector plates.

- Web - The members that join the top and bottom chords to form the triangular patterns typical of trusses.

 

Roof Classification Depends on :-

-Area covered

- Materials available

- Type of lighting

- Ventilation needed inside

- Available appliance

Classification of Roof :-

- Gable Roof

-Gambrel Roof

- Hipped Roof

- Mansard Roof

- Flat Roof

- Shed Roof

  Sketches of different types of roof:-

 -  Gabled Roof: - There are many types of gabled roofs (roofs that essentially look like triangles from the front of the home). I enjoy the cross gabled roof which is used in homes with extra wings so that each portion of the home has its own triangular gabled roof as seen in this photo.

-Gambrel: - This type of roof is very similar to the Mansard Roof. The core differences are that the gambrel has vertical gable ends and the roof hangs over the facade of the home whereas the Mandrel Roof does not. Additionally this one is Dutch-inspired instead of French.

-  Hip Roof: - This roof is very similar to the pyramid roof. The difference is that instead of coming to a point at the top the four sides meet at a ridge or a flat spot like we see here. This is architecturally more practical.

The hip roof is slightly more difficult to build than a gable roof. It is a popular choice, but does not provide for ventilation as well as some designs.

-  Mansard Roof: - This type of roof is made up of four slopes, two on each side of the home. The lower slope is a steeper, more vertical slope than the upper slope. The upper slope may or may not be visible from the ground. This French style of roof allows for additional living space or storage space at the top of the house.

-  Flat Roof: - This type of roof is obviously easy to identify! The benefits of a flat roof include that it's easier to construct, safer if you're going to stand on top of it and generally more accessible. The main drawback is that this type of roof requires more maintenance than other roofs in large part because debris will gather on the roof with nowhere to go.

-  Shed Roof: - A shed roof is similar to a flat roof but has more pitch. It is frequently used for additions or with other roof styles.

DESIGN OF ROOF & ITS  FACTORS : -

-      Specific Loads on roof: -

-   The most common loads falling  within the roof load width are:

-  Gravity Dead loads including roof  and ceiling materials  - these are felt by the structure all of the time

-   Gravity live loads including People  working on the roof  and stuff  stacked on it  - these are only felt some of the time by the structure

-   Wind loads including downward pressure or suction that lifts upward – these are only felt some of the time but downward pressure adds to the gravity loads above, while uplift works in the opposite directions.

  

 ROOF COVERING: -

Is a materials which gives a protective surface to the roofing structure The function is only to prevent ingress or egress of heat & moisture into the building

-  Thatch- is the craft of building a roof with dry vegetation such as straw, water reed, sedge, rushes, or heather. Now become choice for rustic look and more ecologically friendly roof.

-  Wood- thin, tapered pieces of wood primarily     used to cover roofs and walls of buildings to protect them from the weather

-  Shingles- roof covering consisting of individual overlapping elements. Can be made of various materials such as wood, composite or ceramic.

-  Tiles-made of a ceramic material and is hard and brittle, poorly suited for places where tree limbs can fall on a house's roof.

-  Slates - is a fine-grained, foliated, homogeneous metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash

-  Asphalt – known as bitumen, viscous liquid or semi solid form of petroleum.

-  Asbestos cement sheets-known as fiber cement sheet. It is a building material in which asbestos (silicate mineral) fibers are used to reinforce thin rigid cement sheets.

  

-  Corrugated iron sheets-The corrugations increase the bending strength of the sheet. Normally each sheet is manufactured longer in its strong direction.

-  Bituminous felt-bitumen mixed with a filler component such as limestone or sand or polymers to gives rigidity and tear resistance.

-  Sheet metal roof coverings (copper, Zink, etc.)-roofing system made from metal piece, or tiles.

ROOF VENTILATION: - The term “roof vent” can mean many things. As we define it, a roof vent is designed to remove hot air and moisture out of your attic.

- TYPES OF ROOF VENTILATION: -

o   Ridge Vents

o   Turtleback Vents (Box Vents)

o   Power Fans

 RIDGE VENT: - Ridge vent is the best and most consistent system to install. It is installed on the very top of your home at the ridgeline. This is the most natural and cost effective solution to your ventilating needs. Although ridge vent is considered to be the best type of ventilating system it does have one main drawback. If you have a high, hip style roof with little to no ridgeline it may not be suitable for ridge vent.

  TURTLE VENT: - Turtleback vents are typically installed a couple of feet below the ridgeline. This brings us to our first drawback. Because the turtleback vent does not go all the way to the top of the roof it leaves a pocket of air trapped above the vents. Unlike ridge vents, which run continuously across the ridgeline, turtleback vents are seperate units usually placed a few feet away from each other. This allows for gaps in your system and leaves hot and cold areas in your attic space.

  POWER FANS: - power fans draw a great deal of heat out of the attic fast it's still a mechanical based system. This means it is more susceptible to burning up and breaking down. This can lead to costly service calls and expensive electric bills. A power fan runs on electricity and is connected to a thermostat. The thermostat regulates when the fan should turn on and off. However if it's not working properly or installed wrong it may not turn on. In some cases the power fan may also run continuously. Another drawback is there may be a noticeable noise difference when running. Often times after evaluating a customer’s vent system.

MODERN TYPES OF ROOF COVERINGS FOR INDUSTRY: -

3 Layer U PVC Sheets :-

1 Trapezoidal Profile

2.Round Wave Profile/Corrugated

 Properties of UPVC Sheets: -

1.      Chemical Resistance

2.      Fire Resistance

3.      Strength Capacity

4.      Sound Insulation Property

  Size  of UPVC Sheets:-

1.      For 1 mm Thick sheet  lengths are available in 2mtr,2.5mtr  and 3 metre

2.      Width of the Sheet is Internationally Standard that is 1130 mm

3.      Thickness of Sheets is available in 1, 2, 2.5, 3.

4.      For 1mm Thick UPVC Sheet, Purlin Distance should be kept 60 Cm.

5.      For 2/2.5/3mm Thick UPVC Sheet, Purlin Distance should be kept 1 metre.

WATER PROOFING

WATER PROOFING

WHAT IS WATER PROOFING?

Waterproofing is a method by which an item is made resistant to damage by water.

A mortar or concrete is considered impermeable when it does not permit passage or flow of water through its pores or voids.

 Waterproofing is the formation of an impervious barrier which is designed to prevent water entering or escaping from various sections of building structures. Internal areas that are waterproofed include bathrooms, shower recesses, laundries and toilets. Whilst an External area waterproofed extends to roof, terrace, basement floor, exterior surfaces of walls, balconies, retaining walls and swimming pools.

INTRODUCTION

Waterproofing is one of the most important parameters considered in the construction of building and structures to prevent leakages, dampness etc and making the structures durable.

Waterproofing is defined as a treatment of a surface or structure to prevent the passage of water under hydrostatic pressure.

In waterproofing, we will discuss on waterproofing terraces, balconies and flat roofs.

Also we will discuss on both waterproofing of old structures andwaterproofing of new structures.

The aim of this is to reduce the frequency of problems which may be traced back to incorrect design specifications and problems caused by incorrect installation techniques.

Water will cause serious and continuing problems in buildings and building materials unless its effect is understood and provided for in the construction details.

Most of the water leakage problems, more than 50% of claims for damages involve infiltration, while more than 60% of these claims are due to problems with the waterproofing layer.

For waterproofing latest advanced technologies are being used worldwide.

It is caused by poor detailing, poor workmanship, inferior materials or any combination thereof. 

WHY WATER PROOFING IS REQUIRED?

Seepage or leakage is percolation of water through the voids or spaces of the material.

Seepage may occur through defective water pipes, sanitary fitments or drainage pipes, etc.

To overcome this problem of seepage, waterproofing of structure is necessary.

Waterproofing helps to maintain the beauty and increase the life of the structure

NEED OF WATERPROOFING

Leakage

The water leakage term in buildings is used to mean the coming out of water from components like walls and floors of the buildings.

Dampness

Moisture is present in the materials of the building itself, and the air within the building.

Moisture movement

To effectively weather-proof our buildings, we need to understand how and why water behaves as it does. 

REASONS FOR WATER LEAKAGE

Defects due to poor maintenance

§  Filling of joints

§  Joints in floor of toilets

§  Improper use of toilets

§  Replacement of traps

Defects in construction

§  Defective concrete

§  Door frame joint near toilet

§  Plumbing

§  Push cocks

§  Rain water spouts

§  Sill to terrace door

§  Water-proofing of terrace

Defects in design

§  Design of floor slab

§  Design of rain water spouts

§  Fixing of nahni traps

§  Relief valves

§  Slope of terrace slab

TYPES OF WATERPROOFING

SHEET MEMBRANE WATERPROOFING (SLAB)

Lose laid – PVC, HDPE, etc.

Bonded – self-adhesive, hot applied.

PROCEDURE FOR ROOF SLABS

The concrete surface shall be cleaned thoroughly of all laitance, loose particles, dust, grease, etc.

Defects like honey combing ,cracks ,if any ,to be repaired by bonding agent enriched cement-sand(1:4) mortar after applying sika raintite enriched cement slurry.

Surface is then thoroughly saturated with water and should be in surface saturated condition.

Apply one coat of cement slurry enriched with sika rainite (SR:W:C=1:2:3, all by volume) on the roof slab surface and  also up to a height of 150mm on vertical surface of the parapet wall.

On drying of first coat, apply second coat of similar cement slurry admixed with sika rainite for bonding effect.

While the second coat of cement slurry with sika raintite is still tacky, a screed concrete of mix 1:1.5:3 admixed dosage of plasticizer shall be 0.2% on weight of cement, the concrete shall be cured with water in usual manner and continued for 10 days.

LIQUID WATERPROOFING

Liquid Waterproof membranes consist of polymers and bitumen.

These membranes are extensively used for the purpose of sealing terraces, balconies, bathrooms, etc.

Finally, these waterproof membranes have high adhesive property

BENTONITE WATERPROOFING

Bentonite is a type of clay having the unusual characteristics of cohesion, binding, sealing, and thickening.

It is usually grey in colour and when processed has the consistency of fine powder, similar to cement or flour.

BOX TYPE WATERPROOFING (RAFT SLAB & BASEMENT WALL)

Raft slab

20 mm thick cement mortar in CM 1:4 admixed with chemicals shall be laid on the prepared surface.- 15 to 20 mm thick rough kota stones are laid over cement mortar bed with 15 mm gap between two kota stone.- Joints between stone slabs are raked and cleaned. cement grout is filled in joints.- A protective layer of 20 mm cement mortar is laid over the stone slab.- over that reinforcement with proper covering is placed.- after pouring of raft slab, at the Top surface, zigzagnozzling is done for grouting purpose.

Basement walls

 Rough finished low porosity stone slabs 15-20mm thick are fixed with the help of cement paste applied on the internal face of stone slabs, leaving a gap of 15 to 20 mm between the external face of RC wall and internal face of the stone slabs. The stone slabs are fixed side by side without leaving any gap between the edges. In order to fix the bottom most layer of stones a grooves is made in top layer of base treatment and stone slabs fixed in it to ensure the water tightness at the junction of wall and raft.- Maximum 2 to 3 layers of rough stones are laid at a time.-15mm thick cement plaster in CM 1:4 is applied to the external face of rough stone.- The gap between the wall & stone is filled with chemical admixed cement grout, which forms an impermeable monolithic layer.- Holes are drilled on the inner face of RC wall at 1.2mc/c over the entire wall surfaces in the grid pattern.-GI or PVC nozzles are fixed in these holes with cement and allowed to set. -Cement slurry admixed with non-shrink expanding grout should be injected throughout the network of nozzles by low pressure hand pump until refusal.- The protruded end of the nozzles shall be cut and sealed off after the grouting operations are over.

WATERPROOFING MATERIALS

Acrylic based polymer coating

Variations of temperature causes micro cracks in concrete and these micro cracks propagate with time.

Also structural inadequacy or failure to adhere to poor detailing of reinforcement, or unequal settlement etc is some of the additional reasons for development of cracks in concrete members.

In such situations a membrane forming waterproofing material is ideal. The membrane should be tough, water resistant, solar reflective, elastic and durable.

Chemical DPC for rising dampness

Often old buildings are not provided with a DPC.

The water from the ground rises due to capillary action. This water brings with it dissolved salts and chemicals which affect the durability of the structure.

Now we have materials that can be injected into wall at appropriate level to seal the capillaries and thereby to stop upward movement of water.

Waterproofing adhesive for tiles, marble, and granite

Silicon based water repellent material

When for aesthetic purpose transparent water proofing treatment is required then silicon based water repellent materials are used. These materials form a thin water repellent film on the surface.

These types of waterproofing materials are used in many monumental stone buildings and old places so that the original look of the stone masonry can be maintained.

Injection grout for cracks

It is one of the most powerful methods commonly adopted for stopping leakages in dams, basement, swimming poolsand construction joints and even in leaking roofs.

This method is useful for gravity as well as pressure grouting and is a powerful method for strengthening and waterproofing of unhealthy structures.

Joint sealants

Joints in buildings, bridges, roads and airfields pavement are inescapable. They may be expansion joints, construction joints, or dummy joints.

Such gaps should be effectively sealed using sealants. Now-a-days we have modern materials like polysulphide sealants and gun applied silicon rubber sealants.

These are manufactured and sold under various trade names, and are available in powder or liquid form, e.g.: “SAHARA”, “POZOLITH”, “AQUELLA”,  “ZILICON”, “ANTI-HYDRO”

PRECAUTIONS

§  See that all the material used is of good quality.

§  See that the traps and release pipes are fitted properly before brick-bat coba coat.

§  See that all the bricks are well soaked in water before use.

§  Observe minimum gap between the brickbats.

§  Check the slope in brick bat coat, towards the tap.

§  See that waterproofing compound is mixed in mortar at every stage of work.

§  Observe proper finishing near spouts.

§  Check each stage by flooding it by water for leakage.

§  Cure the surface without interruption.