Timber roof

TIMBER ROOFa) Lean to roof

b) Collared Roof

c) King post roof

d) Queen Post Roof

1Presentation By- Ar. Roopa Chikkalgi

Classification of Roof

2

Roof is classified as per functional requirements. The

roofs are mainly classified into three types.

•Pitched or Sloping Roof

•Flat Roof or Terrace Roof

•Shell Roofs or curved Roof

a) Single roofs• Lean-to-roof

• Couple roof

• Couple-close roof

• Collar-beam roof or collar tie

b) Double or purlin roofs

c) Triple-Membered or Framed or Trussed Roof•King-post roof Truss

•Queen-post roof Truss

•Combinations of King-post and Queen-post Trusses

•Mansard roof Truss

•Truncated roof Truss

•Belfast roof Truss

•Composite roof Trusses

•Steel sloping roof Trusses

Presentation By- Ar. Roopa Chikkalgi

TIMBER ROOF■ A timber roof truss is a structural

framework of timbers designed to bridge

the space above a room and to provide

support for a roof.

■ Trusses usually occur at regular

intervals, linked by longitudinal timbers

such as purlins. The space between

each truss is known as a bay.

■ Truss is basically a triangle or arch

shapes frame used the majority in roof

cover it.


Lean to Roof■ The lean to roof is defined as single slope roof with its upper edge adjoining a wall or

building.

■ This is the simplest type of pitched roof consisting of rafters sloping on one side only.


■ Lean to roof is a free standing structure. The wall of one side of the room is

taken higher than the wall on the other side.

■ Length of this roof is suitable for maximum span of 2.5 meters.

■ This lean to roof is constructed against an existing wall or other roof.

■ Main use of this roof is for constructing sheds, simple extensions, car ports,

for covering verandahs, etc. When any storage building will require additional

space than the lean to roof is constructed with existing wall.

■ Construction of lean to roof is easy and inexpensive.

■ Due to slope of the roof, water and snow easily run off and reduces

necessary extra waterproofing.

■ So this roof is best for constructing in high rain fall and snow fall regions.

This may be done either as a part of original construction or even during

execution after some year.

■ In this roof, the roof covers may be of Mangalore tiles, A.C sheets or even

pre-coated sheet and this roofing sheet also add beauty to the structure

apart from it functional use.

■ This roof is not adequate for a long span where its width is more as

minimum clearance of 2.0 m to 2.5 m at eaves level is needed.5Presentation By- Ar. Roopa Chikkalgi

Lean to Roof


Collar Beam Roof■ A collar beam or collar is a horizontal member between two rafters and is very common in

domestic roof construction. Often a collar is structural but they may be used simply to frame a

ceiling.

■ In this Roof, Horizontal tie is raised up from the feet of the rafters to almost middle of the rafters.

This raised up horizontal tie is known as the collar Beam. Collar beam should not be fixed more

than one-third or one- half of the rise of the roof up from the wall plate.


■ Collar beam is used to prevent spreading the foot of the rafter. When the span increases, or when

the load is more, the rafters of the couple close roof have the tendency to bend. So in this

condition, the raising-up of collar beam checks the tendency of sagging due to further increase in

span or excessive loading conditions.

■ This collar beam roof is suitable for the span varying from the 4 to 5.5m. This roof is used for

maximum span of 4.8 m.

■ Disadvantage of this collar roof is that the head of the windows formed in a wall will be some

distance below ceiling and give less penetration of light.

■ So in this collar beam roof, dormer window is provided which is partly built into the wall and party

in the roof.


SHEET NO.1■ A1 SHEET ON Timber Lean to roof & Collared roof IN 1:10 SCALE

■ With one Interesting detail of the joinery for each roof type in 1:5 Scale.


Presentation By- Ar. Roopa Chikkalgi 10

King Post Roof Truss■ Truss is basically a triangle or arch shapes frame in roof to cover it.

■ A King post is a central vertical post used in architectural or bridge

designs, taking tension to support a beam below from a truss above.

11


■ In king post truss, purlins are supported by principal rafter. The purlins support the closely spacedcommon rafters.

■ The slope of common rafters is same as that of principal rafter. The common rafters support the roofcovering.

■ In king Post Roof truss, The Bottom chord of the truss is act as tie beam and this tie beam receives theends of the principal rafters and prevents the wall from spreading out due to thrust.

■ The vertical king post is used to prevent the sagging of tie beam at centre of span. The Struts areconnected to the tie beams and the principal rafters in inclined direction. The Struts are used to preventthe sagging of principal rafters.


Presentation By- Ar. Roopa Chikkalgi 13

• Ridge beam is provided at the apex of the roof to provide end support of the common rafters. The trussesare supported on the bed blocks of stone or concrete which is fixed in the supporting walls.

• The Spacing of King Post truss is limited to 3 m centre to centre. The truss is suitable for spans varying

from 5 to 8 meter.• It is not suitable for long span.• The king post truss does not provide storage space, because the frames are usually exposed and does not

allow extra room.• King post truss is used when there is a need to support the weight of an expansive roof.• This roof provides not only functionally, but also adds beauty as well.• The king post truss is also used for simple roof lines and short span bridges.

SHEET NO.2■ A1 SHEET ON King post roof IN 1:10 SCALE

■ With two Interesting details of the joinery for the roof type in 1:5 Scale.


Truss is basically a triangle or arch shapes frame used majority in roof

cover it.

Queen Post truss is defined as a pitched roof support using two

vertical tie posts connected between the tie beam and the rafters

Queen Post Roof Truss


■ The wooden queen post roof differs from a king-post truss in having two wooden uprights or vertical

member which is known as queen post. In this roof, Queen – posts is used instead of king post.

In this roof, The Queen posts are the tension members which are used to prevent the sagging of tie

beam.

A straining sill is fixed on the tie beam and also fixed between the feet of queen post. This straining

sill is used for reducing the thrusts from struts. The principal rafters, Straining beams, struts and

straining sill are in compression whereas the queen posts and tie beam are in tension.

Purlins are horizontal wooden members laid on principal rafters on wall-to-wall to support common

rafter of a roof which is fixed with cleat.


17

• Queen post trusses are suitable for 8 to 12 meters.• These trusses are made from a variety of materials such as timber or steel.

• The Queen post truss is simpler and lighter in weight. It does not put weight on the centre of the

main tie beam, as the king post truss.

• Queen post trusses are used when there is a need to cover large areas.

• They are relatively low-cost and can be made to fit almost any size or slope of roof.

• It can also provide striking ceiling design that differentiates a home.


SHEET NO.3■ A1 SHEET ON Queen post roof IN 1:10 SCALE

■ With two Interesting details of the joinery for the roof type in 1:5 Scale.


King Post Roof Truss Queen Post Roof Truss

A king post has a central vertical post as used in

architectural or bridge designs, working in tension to

support a beam below from a truss apex above.

Queen Post truss is define as a pitched roof support using

two vertical tie posts connected between the tie beam and

the rafters.

The king post roof truss consists following components:

Tie Beam

Two Inclined principal rafter

Two struts

King post

Ridge Beam

The Queen post Truss consists of following components.

Two Queen posts

Two Principal Rafters

Struts

Tie Beam

Straining beams

Straining sills

Purlins

King post roof truss is used when the length of span is in

the range of 5 to 8 m.

Queen post roof truss is used when the length of span is

in the range of 8 to 12 m.

One vertical post is provided at the centre of the roof

which is called king post.

Two vertical posts are provided in 2 sides at distance

which is called queen post.

Straining beam and straining sill are not necessary. Straining beam and straining sill are used to keep the

queen post in stable position.

King-post is connected with principal rafter, strut and tie

beam.

Queen-post is connected with principal rafter, strut,

Straining beam, straining sill and tie beam.

The top ends of two main rafters are connected to ridge

pitch.

Top ends of two main rafters are joined with the queen

posts heads. 19Presentation By- Ar. Roopa Chikkalgi

Timber roof

Education