A report on roof covering materials by noidarocker

VIEWS: 3 PAGES: 11

									Guided By - Ar. Sandeep Mishra

Submitted by –

Akshat Garg , Alok Kumar Maurya, Ankita Manglik , Komal Yadav ,
Nitya Singh

     B. Arch. IV Yr.

                  Department of Architecture, B.B.D.N.I.T.M., LUCKNOW.
A Roof is the covering on the uppermost part of a building. A roof basically consist of
roof covering materials supported on structural elements installed on building top. The
structural elements may be trusses, portals, flat slab, shell, dome or space frame.
Whereas the roof covering material may be thatch, wooden shingle , tiles, slates, A.C.
sheets , G.I. sheets etc.

A well planned roof should be –

      Structurally sound.
      Durable against adverse effects of elements like rain ,snow, sun ,wind.
      Efficient water proofing & drainage systems.
      Provide desirable insulation against heat & sound.
      Reasonably priced.
      Aesthetically attractive




History of roof coverings –
The earliest roof used readily available materials from the surrounding terrain and
needed to be portable. Most likely the first roof was covered with dirt, underlayed with
branches and supported by wooden beams.


                                                       The Sod Roof system is one the
                                                       original "Green Roofs" and one
                                                       of the oldest flat roofing
                                                       systems know. Dirt roofs might
                                                       be the oldest flat roofs ever
                                                       made. Although Sod Roofs are
                                                       ancient    in   design,   early
                                                       American settlers in the Great
                                                       Plains used this design in the
                                                       1800's.



                    Department of Architecture, B.B.D.N.I.T.M., LUCKNOW.
   Over 30,000 years ago, Aborigines used bark from birch trees for their roofs. But
in places like Siberia where birch trees were not available, hunter gathers
used        mammoth        skins       to       cover        their        dwellings.



                                             Mamoth Skins are one of the oldest
                                             roofing    materials      known to
                                             mankind. The whale skin huts would
                                             have been similar in design.




             More advanced civilizations used thatch and reeds to build dwelling
roofs. The dwellings were more permanent structures but were designed to be easily
dismantled because of spring floods. Later these dwellings became permanent when
                             built on piled or rock foundations.



                              The Thatch Roof dates back to around 30,000
                              BC.     This     style    of     roof is still
                              being used in parts of Africa where climates
                              although for use of such housing




Natural asphalt was first used as early as 30,000 BC as a
waterproofing technique, something that is still used today. Ceramic tiles, another
familiar roofing product, was created around 10,000 BC by the Chinese and shortly
after in the Middle East.



Clay Tile roofs are the oldest roofing
product to still be used today. The
Chinese developed Clay baked tiles
around 10,000 BC. Shortly after Clay
Tiles were produced in the Middle East.




                   Department of Architecture, B.B.D.N.I.T.M., LUCKNOW.
Classification of roofs –

   1) Flat or Terraced Roof
   2) Pitched or Sloped Roof
   3)
Flat roof –
Properties -
1) A roof is designated as flat id its slope is less than ten degrees.
2) Flat roofs have traditionally been used in hot climates where water accumulation
is not a problem.
3) They were generally unkown in northern climated before the end of the last
century.

Advantages of flat roof :
1) No space lost below roof, i.e. no dead space
2) Less material is used than in a sloped roof
3) The rooftop is potentially useful as a terrace, or sleeping porch
4) Potentially pleasing appearance
5) Easier to build than a sloped roof

Disadvantages of flat roof :
1) Roof elements can not overlap, hence waterproofing must be more complex, and
more thorough
2) Drainage is not automatic
3) Support of snow load must be insured


Pitched roof –         it is the cheapest alternative for covering the structure. This is
generally constructed in wood or steel The pitch is the angle at which the roof rises
from its lowest to highest point. Most domestic architecture, except in very dry regions,
has roofs which are sloped, or pitched. example thatch, require a steep pitch in order
to be waterproof and durable.[1] Other types of roofing, for example pantiles, are
unstable on a steeply pitched roof but provide excellent weather protection at a
relatively low angle.

Advantages –

       These are light in weight.
       It can be used for long span without introduction of the intermediate supports.
       Drainage is automatic.

                     Department of Architecture, B.B.D.N.I.T.M., LUCKNOW.
      Leakages can be easily detected.
      These roofs are preferable in heavy rainfall and snowfall area.
      Easy to install and rapid in construction as there is no need of formwork.

Disadvantages –

      Noisy
      Thermal insulation is not better as of flat roof.
      Roof top is not accessible.
      It cannot resist heavy wind pressure.
      Being softer these sheet are more likely to tear away in heavy storm.
      Having greater thermal expansion results in noisy creaks and more stress on
       fasteners.
      It cannot be used in multi-storied buildings.

Parts of a roof
There are two parts to a roof, its supporting structure and uppermost weatherproof layer. In a
minority of buildings, the outer layer is also a self-supporting structure.

The elements in the design of a roof are :-

      the material
      the construction
      the durability

The material of a roof may range from banana leaves, wheaten straw or seagrass to lamininated
glass, aluminium sheeting and precast concrete. In many parts of the world ceramic tiles have
been the predominant roofing material for centuries.

The construction of a roof is determined by its method of support and how the underneath
space is bridged and whether or not the roof is pitched. In regions where there is little rain, an
almost flat roof with a slight run-off provides adequate protection against an occasional
downpour.

The durability of a roof is a matter of concern because the roof is often the least accessible
part of a building for purposes of repair and renewal, while its damage or destruction can have
serious effects.

   Roof covering material                  – There are an enormous variety of roofing materials,
   selection is based on price, durability, appearance, roof slope

For pitched roofs:

            Wood
            Asphalt shingles

                       Department of Architecture, B.B.D.N.I.T.M., LUCKNOW.
           Slate
           Tile
           Metal




      Asphalt shingle - There are two kinds of asphalt shingles on the market:
       Fiberglass shingles and organic-mat shingles. Fiberglass shingles are thinner,
       lighter, easier to lug around, and carry a better fire rating than organic shingles.
       Organic-mat shingles are tougher and stay more flexible in cold weather.
       Fiberglass shingles predominate in southern and central regions, but organic
       shingles are still popular in the North and are almost the universal choice in
       Canada. In practice, organic shingles have a much higher tear strength and
       nail-pull resistance than fiberglass shingles.

Asphalt shingles composed of

          o   Felt or fiberglass substrate, impregnated with asphalt
          o   Mineral surface sprayed on surface
          o   Adhesive seal-down strips at midpoint.
          o   Multiple layers in architectural (built-up) shingles




                    Department of Architecture, B.B.D.N.I.T.M., LUCKNOW.
Asphalt shingles Properties -

      Asphalt shingles are an economical versatile roofing solution.
      They're relatively inexpensive to buy and install, are suited to roof pitches from
       4-in-12 to vertical.
       available across a wide range of quality, cost, and style.
      Easy to cut, fit, and fasten, asphalt shingles are compatible with many different
       kinds of flashing and edging products.
      They don't require specialized accessories for roof edges, wall terminations,
       chimney or vent
      Shingle must resist abrasion from elements, degradation from UV, loss of
       asphalt due to drying (heat), etc.
      Shingles carry warranties of 15 to 40 years depending on the amount of
       material used to make the shingle. Weight per square varies accordingly.
   




                    Department of Architecture, B.B.D.N.I.T.M., LUCKNOW.
 Wood shakes and shingles
     Shakes are rough surface (hand split
       or similar) and provide heavy
       shadow lines
     Shingles are sawn and are used for
       siding as well as roofing
     Cedar shingles are the most
       common, they are expensive and
       must be treated with fire retardant




 Slate-
      A very long-lasting roof, and quite
         expensive.
      Roof framing must be reinforced for
         the weight
      Slate should not be walked on if old
      Can be repaired with clip, normally
         fastened with copper nails in pre-
         drilled holes




 Tiles –
       Clay and Cement tiles used very commonly in warmer climates.
       Roof framing must be reinforced
       Applied with mortar or using nails
       Traditionally applied over purlins, nailed to sheathing today




               Department of Architecture, B.B.D.N.I.T.M., LUCKNOW.
 Metal roofing
     Recent improvements in paint quality and life have brought more
        painted steel roofs into the residential market.
     Cost competitive with asphalt shingles, and longer lasting, used
        commonly for agricultural structures
     Attached with gasketed nails or more commonly with gasketed
        screws




              Department of Architecture, B.B.D.N.I.T.M., LUCKNOW.
 For low slope and flat
  roofs
      Roll roofing
      Membrane
      Built-up

 Roll roofing
      traditionally used for
         low-slope residential
         work.
      Available in single and
         double coverage.
      Very inexpensive, but
         considered unattractive
      Applied with nails and
         tar, tar typically leaks
         out at edges
 Membrane roofing
      “Rubber” roofing (EPDM) and other similar materials come in sheets or rolls,
         are glued or ballasted to the roof, and seams are heat or solvent welded.
      Materials are relatively expensive, but roof is long lasting and stays flexible.




 Built-up roofing – multiple layers of felt and tar applied to a roof
  deck, and then the surface is covered with ballast.

        Labor intensive, nasty materials, and dangerous work, but it
         used to be the only way to get a waterproof flat roof




                 Department of Architecture, B.B.D.N.I.T.M., LUCKNOW.
Department of Architecture, B.B.D.N.I.T.M., LUCKNOW.

								
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