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King post, queen post, mansard trusses; thatch

Short answer

King post truss has one vertical member for 5-8m spans; queen post has two posts for 8-12m; mansard has double slopes (lower 60-70°, upper 15-30°) for attic space. Thatch is cheapest, insulates well, light, and quick to repair but has high fire risk, short life (3-5 years), harbours pests, needs steep slope, and poor rain protection.

Compare king post, queen post and mansard roof truss with suitable sketch. What are the advantages and disadvantages of thatch roof covering?

Comparison of king post, queen post and mansard trusses

PointKing post trussQueen post trussMansard truss
Vertical membersOne king postTwo queen postsKing and/or queen posts
Span5-8 m8-12 mLarge spans with attic
Top memberSingle slope principal raftersStraining beam between postsTwo slopes each side
SlopeSingle, 30-45 degreesSingleLower 60-70, upper 15-30 degrees
UseHouses, small hallsHalls, godownsAttic rooms, public buildings
ComplexitySimpleMore jointsMost complex
 King post        Queen post        Mansard
    /\               /\             ____
   /|\              /--\           /    \
  / | \            /|  |\         /      \
 /__|__\          /_|__|_\       |________|

Thatch roof covering

Advantages: cheapest and locally available (straw, khar, reed); good thermal insulation (cool in summer, warm in winter); light weight, so light supporting structure; quick to lay and repair. Disadvantages: high fire risk; short life (3-5 years) and frequent replacement; harbours rats, insects and moulds; needs steep slope (45-60 degrees) and is not easily rain-proof; poor appearance and not suitable for urban areas.

✓ Answer checked by Claude Opus 5.5 (high effort)

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