• King-post, truss
• Queen post truss
• Combination of king-post and Queen post truss
• Mansard truss
• Truncated truss
• Bel-fast truss
• Steel truss
• Composite trusses.

King-post truss

Any king-post truss consists of the next components

1. lower strap beam,
2. pair inclined principal rafters,
3. two struts, and
4. a king post.

• The principal rafters support the purlins.
• The purlins support the nearly-spaced common rafters which own the same slope as the principal rafters.
• The common rafters support that roof covering as usual.
• The spacing from the kingpost truss is limited to 4 m middle to middle.
• The truss is suitable to spans varying from 5 into 8 metres.
• The principal rafter is jointed to the tie-beam with a single abutment and ‘tenon joint’ or by a ‘bridle joint’.
• The collective is further strengthened by a wrought iron heel strap, would round the joint.
• The king-post is provided among splayed shoulders and feet and is tenoned toward the upper edge of the tie beam for a sufficient distance.

Queen-post truss

• A queen-post truss differs of a king-post truss in having two vertical posts, rather than one.
• The vertical posts are known as queen-posts, these tops of which are correlated by a horizontal piece, known as straining beam.
•  Two struts are provided to join the feet of any queen-post to the principal rafter, The queen-posts are the tension members.
• The straining beams receive the thrust from the principal rafters and keep the junction in a stable position.
•  A straining beam is introduced on the tie beam within the queen-posts to counteract each thrust from inclined struts which happen in compression.
• In absence of the straining sill, the thrust from the strut would serve to force the foot of the queen-post inwards.
• These trusses are suitable for spans between 8 to 12 metres.
• The joint at that head of queen-post -is formed due upon the junction of pair compression members (principal timber plus straining beam) and each tension member(queen-post).

Combination of king-post and queen post truss

• King post and Queen-post trusses are suitable for spans up to 12 meters.
• For greater spans, the queen-post truss can strengthen by one more upright member, called princess-post to each side.
•  Fig. display the resulting combination of king-post also queen-post trusses, which are becoming up to 18 m spans.

Mansard roof truss

• This roof truss called given on its designer Francois Mansard, a French planner.
• A mansard roof truss does a combination of king-post and queen-post trusses.
•  It is a two-storey truss, with upper-division consisting of king-post truss and the lower portion of a queen-post truss.
• The entire truss has two pitches. The upper pitch (king-post truss) varies from 30° to 40° while two lower pitch (queen-truss) varies from 60° to 70°.
• The use of these truss results in an economy in space.

Truncated truss

• A truncated truss is comparable to Mansard truss, except that its head is formed flat, with some gentle slope to one side.
• This type of truss is used when it is required to provide a room in the roof, between the two queen-posts of the truss, as shown in Fig.

Bel-fast roof truss (Bowstring truss)

• This truss, in the form of a bow, consists of thin sections of timber, with its best chord curved.
•  If this roof covering is light, the roof truss can be managed up to 30 m.

Composite roof trusses

• Roof trusses made of two materials, such because timber also steel, are known as composite rooftop trusses.
• In a composite truss, the tension members are made of steel, while compression members are made of timber.
• If tension members are made of timber, their section becomes very heavy because of the reduction of a section at the joints.
• Special fittings mean required to the junction of steel and timber members.

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