Roofs

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Roofs
Roofs are one of a buildings primary elements
and play a major part in giving a building its
character.
There are several different types of roof in this
one building.

• Subtitle

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A roof must have the following qualities

• A roof must be weather resistant to rain, snow,
  wind and sun.
• The durability of a roof should be equal to or in
  excess of those materials used in the remainder
  of the building.
• A roof should have good thermal insulation
  properties.
• A roof should require a minimum of maintenance.
• A roof should be constructed in such a way as to
  retain structural stability when dead and imposed
  loads are applied to it ( dead loads is the
  weight of materials used to make the roof,
  imposed loads are loads created by wind, snow,
  etc.

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Roof Elements

• When designing a roof the following points
  should be considered in relation to its final
  appearance.
• Pitch
• The steeper the pitch the greater the roof area
  visible. This will result in a larger roof space,
  you can also use smaller cladding units such as
  plain tiles and slates. Pitched roofs are the
  most suitable in countries where there is a high
  rain fall.
• Coverings
• Materials used for roof coverings should
  harmonise with the local surroundings. These
  materials
• should be fit for purpose in their
• ability to keep out the elements,
• thermal insulation, durability and
• appearance.

Concrete interlocking roof tiles
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Roofs
Valley Rafter
Ridge
Hipped End
Verge
Jack Rafters
Common Rafters
Hip
Eaves
Gable End
Lean-to Roof
Flat Roof
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Terminology

• Wall plate
• Usually 100 x 50 mm softwood timbers are fixed to
  the top of
• load bearing walls to distribute loads and
  provide fixings for
• roof timbers.
• Ceiling joist
• These are timbers which provide a support for
  fixing ceiling
• finishes and act as a collar to prevent rafters
  spreading.
• Common rafters
• These are inclined timbers fixed between wall
  plate and ridge
• which transmit live and dead loads to wall plate.
• Ridge
• The ridge is a horizontal board set on edge to
  which the
• rafters are attached (not required on trussed
  rafters).

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Terminology

• Hip Rafter
• A hip rafter is a rafter running from the wall
  plate to the ridge
• which forms the external angle of the sloping
  side of a roof.
• Purlin
• This is a horizontal roof member supporting the
  rafters and
• usually at right angles to these. This enables
  small section
• timbers to be used for the rafters.
• Hangers
• These are timbers hanging from the purlins to the
  ceiling joist
• to give additional support to binders.
• Fascia
• A board fixed vertically to rafter ends, which
  provide an additional fixing
• for gutters.

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Terminology

• Soffit
• A horizontal board fixed to the underside of the
  rafter outside
• the building.
• Bargeboard
• Verge or gable board.
• Eaves
• The lower part of the roof, which usually
  includes the end of
• the rafter, ceiling joist, soffit, fascia and
  gutter.
• Dormer
• A vertical window coming through a sloping roof.
• Valley
• This is the name for the intersection between two
  sloping surfaces,
• forming an internal angle ( the opposite to a
  hip).

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Pitched roof
If the roof space is or may be intended to be
used in the future, the structure should be
designed accordingly.

• Roof with a gable end

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Hipped Roof
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Pitched roof with dormer windows

• A pitched roof with dormer
• windows.

Timber to support the dormer window
Lay board
When a steep pitched roof is used in domestic
construction dormer windows can be used to create
additional head room in the roof space. This
allows the roof space to be utilised for
habitable rooms.
Common Rafter
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Roof parts
Ridge
Dormer window
Barge board
Gutter
chimney
Down pipe
Door
Eaves detail
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Traditional cut Roof
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Eaves detail pitched roof
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Traditional cut roof structure

• A traditional cut roof was the first development
  to create pitched roofs as we know them today.
• This type of roof structure is still widely used
  for individual dwellings or for roofs of a
  complicated shape.
• The timbers rafters are cut individually and
  nailed into position.
• A purlin is often placed half way up the length
  of the rafter to help support the roof and allow
  smaller sections of timber to be used.

Common rafters
Steel purlin
Pad-stone built into the wall to help distribute
the load of the roof over a larger section of
wall.
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Trussed rafters
A high percentage of roofs designed now are
constructed using prefabricated trussed rafters.
They have been developed since the mid 1960s.
The principal disadvantage is that the roof
space is occupied by a large number of timber
sections.
The following are the main reasons for developing
truss rafters 1.Smaller and light sections of
timber can be used. 2. Speed of erection. 3.
Semi-skilled labour can be used. 4. Eliminates
the need for purlins and ridge boards. 5.
Loadbearing partitions are eliminated, allowing
greater freedom of internal room
arrangements.
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Standard trussed rafter
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Roof coverings
A wide variety of different types of roof
coverings are available including natural
slates man made slates concrete tiles Profiled
metal sheet
Roof tiles
Profiled galvanized metal sheet