CLASSIFICATION

BASED ON NO. OF
SLOPING SURFACES
AND THEIR
INTERSECTION
OF PITCH ROOF

B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
• A roof may be constructed as,
A flat roof, that is made up of a timber, metal or concrete framed platform
which is either horizontal or inclined up to five degrees to the horizontal.
A sloped or sloping roof is inclined over five degrees and up to ten degrees.
Or
A pitched roof with one or more slopes pitched at more than ten degrees to
the horizontal.

B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
 Classification Of Pitched Roofs Based On No. Of Sloping
Surfaces And Their Intersection
LEAN-TO ROOF:
This is the simplest type of sloping roof, provided either for the room of a
small span, or for the verandah or for the parking/storage sheds. It has
slope only on one side.
A free standing version of the lean-to roof is also called as mono-pitch roof.
The butterfly roof is in effect with two monopitch roofs which depend for
support and stability on a central supporting beam or wall.

B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
GABLE ROOF
This is the common type of sloping roof which slopes in two directions. The
two slopes meet at the ridge. At the end face, a vertical triangle is formed
known as gable end.
(The end walls will have vertical triangles at the roof intersection)
The gable can be constructed at any pitch, ( symmetrical or asymmetrical)
with the choice of pitch limited only by the roofing material and the
appearance desired.
A gable roof is often used on designs seeking a traditional appearance
and formal balance.

B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
 The gable can be constructed at any pitch,
(symmetrical or asymmetrical) with the choice of
pitch limited only by the roofing material and the
appearance desired.
B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
A-FRAME ROOF
An A-frame is a method of framing roofs. An A-frame roof structure uses
rafters to form its supporting walls or Rafters are walls of the structure.
The structure gets it’s name from the letter A that is formed by the roof and
floor systems.
The roof plan for an A-frame is very similar to the plan for a gable roof,
However, the framing materials are usually quite different.

B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
GAMBREL ROOF:
This roof is like gable roof, it slopes in two directions, but there is a break in
each slope, i.e. the angle of the roof slope is changed at intermediate
point.
The gambrel roof is a traditional shape that dates back to the colonial
period.
The lower level is covered with a steep roof surface, which connects into
the upper roof system with a slighter pitch.

B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
HIP ROOF:
This roof is formed by four sloping surfaces in four directions. At the end
faces, sloped triangles are formed. (The roof will have total four sloped
surfaces)
The intersection between surfaces is called a hip.
If built on a square structure, the hips will come together to form a point,
which is also known as pavilion roof or pyramid roof.
If built on a rectangular structure, the hips will form two points with a
ridge spanning the distance between them.
The hip roof is a traditional shape that can be used to help eliminate some of
the roof mass and create a structure with a smaller appearance.

B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
 DUTCH HIP / DUTCH GABLE ROOFS:
The Dutch hip roof is a combination of hip and gable roof.
The center section of the roof is framed using a method similar to a gable roof.
The ends of the roof are framed with a partial hip that blends into a gable.
A small wall is (gable end wall) is formed between the hip and the gable
roofs.

B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
MANSARD ROOF:
Mansard roof, like a hip roof, slopes in the four directions, but each slope has a
break, i.e. the angle of the roof slope is changed at the intermediate point.

B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
 DECK ROOF:
A deck roof has slopes in all four directions, but a deck or a plane surface
is formed at the top, i.e. slopes do not meet at top as a ridge.

B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
 TYPES OF PITCHED ROOFS:
CLASSIFICATION BASED ON COMPONENTS

Pitched roofs may be broadly classified into the following:

(a) Single roofs:
(b) Double or purlin roofs:
(c) Triple-membered or framed or trussed roofs:

B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
These Roofs are further classified as following:
(A) SINGLE ROOFS:
• Lean- to Roof
• Couple Roof
• Couple – Close Roof
• Collar beam roof or collar tie roof

(b) DOUBLE OR PURLIN ROOFS:

(c) TRIPLE-MEMBERED OR FRAMED OR TRUSSED ROOFS:

• King-Post roof truss
• Queen-post roof truss
• Combination of King-post and Queen-post roof trusses
• Mansard roof truss
• Truncated roof truss
• Bel-fast roof truss or latticed roof truss
• Composite roof truss
• Steel sloping roof truss

B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
 SINGLE ROOFS DOUBLE ROOF A TRIPLE-MEMBERED OR
TRUSSED OR FRAMED
ROOF
Single roofs consist of A Double Roof is the one A triple-membered or trussed
only common rafters in which purlins are or framed roof consist of
which are secured at the introduced to support the three set of members:
ridge (to ridge beam) and common rafters at the i) common rafters
wall plate. intermediate point. ii) purlins
i.e The function of the iii) trusses
purlin is to tie the rafters
together and, to act as an The purlins which give an
intermediate support to the intermediate support to the
rafters. rafters, are themselves
supported on trusses which
are suitably spaced along the
length of a room.

These are used when span Such roofs are used when A trussed roof is provided
is less so that no the span exceeds 5 metres when the span of the room is
intermediate support is greater than 5 metres, and
required for the rafters. when the length of the room
is large, i.e. where there are
no internal walls or partitions
to support the purlins.

B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
If the span of the roof is less than 5 m the following types of single
roofs are used.
(i) Lean-to roofs
(ii) Coupled roofs
(iii) Coupled-close roof
(iv) Collar beam roof

B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
(B) Double or Purlin Roofs
If the span exceeds, the cost of rafters increases and a single roof
becomes uneconomical. For spans, more than 5 m double purlin roofs
are preferred. The intermediate support is given to rafters by purlins
supported over collar beams.

B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
(c) Trussed Roof
If the span is more, a framework of slender members are used to
support sloping roofs. These frames are known as trusses. A number
of trusses may be placed lengthwise to get wall free longer halls.
Purlins are provided over the trusses which in turn support roof
sheets. For spans, up to 9 m wooden trusses may be used but for
larger spans, steel trusses are a must. In the case of wooden trusses,
suitable carpentry joints are made to connect various members at a
joint. Bolts and straps are also used. In the case of steel trusses
joints are made using gusset plates and by providing bolts or rivets or
welding.

B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya
TRIPLE-MEMBERED OR FRAMED OR TRUSSED ROOFS:
King-Post roof truss
Queen-post roof truss
Combination of King-post and Queen-post roof trusses
Mansard roof truss
Truncated roof truss
Bel-fast roof truss or latticed roof truss
Composite roof truss
Steel sloping roof truss

B. Arch. – II, Sem. - III Building Material & Construction Technology – III Faculty of Architecture, SCET
Presentation Prepared By Prof. Alpa Pandya