Correct Answer: A. Single
Solution:
Single roofs consist only of common rafters that span from the wall plates to the ridge. They are used for short spans (typically up to 5m) as they have no intermediate supports like purlins or trusses.
Correct Answer: D. Lean-to roof
Solution:
A lean-to roof has only one slope and is typically built against a taller wall. It's the simplest type of pitched roof, often used for verandahs, sheds, and extensions.
Correct Answer: D. Couple roof
Solution:
A couple roof is the most basic form of a two-sided pitched roof. It consists of two rafters (a couple) that meet at the ridge, with their lower ends resting on the wall plates. It is only suitable for very small spans.
Correct Answer: C. Couple-close roof
Solution:
In a couple-close roof, a horizontal tie beam is added to connect the feet of the rafters. This crucial member prevents the weight of the roof from pushing the walls outwards.
Correct Answer: A. Collar beam roof
Solution:
A collar beam roof (or collar tie roof) moves the horizontal tie higher up from the wall plate level to create more headroom or a vaulted ceiling effect. This member is called a collar beam.
Correct Answer: A. Collar and scissor roof
Solution:
This design uses two crossing collar beams that resemble a pair of scissors. It provides structural support while also creating a more decorative, vaulted ceiling on the interior.
Correct Answer: B. Purlins
Solution:
Purlins are horizontal members that span between trusses or load-bearing walls. The common rafters then sit on top of these purlins, which effectively shortens the rafter's unsupported span, allowing for smaller, more economical rafters.
Correct Answer: D. Trussed roofs
Solution:
For larger spans, a simple rafter and purlin system is not sufficient. A trussed roof uses a series of engineered trusses to span the entire width of the building, providing a strong, self-supporting framework for the purlins and roof covering.
Correct Answer: B. King post truss
Solution:
A king post truss is identified by its central vertical member, the king post, which runs from the apex of the truss down to the tie beam, preventing it from sagging.
Correct Answer: D. Queen post truss
Solution:
A queen post truss is used for larger spans than a king post truss. It features two vertical posts, called queen posts, which create a larger clear span in the center of the attic space.
Correct Answer: C. Thatch
Solution:
Thatch is a traditional roofing method that uses dry vegetation like straw, reeds, or palm branches layered to shed water. While an excellent insulator, it is lightweight, combustible, and prone to decay.
Correct Answer: D. Shingles
Solution:
Wood shingles are a common roof covering made from splitting logs of durable timber into thin, rectangular pieces. They are laid in an overlapping pattern to ensure water-tightness.
Correct Answer: B. Corrugated Galvanized iron
Solution:
Corrugated Galvanized Iron (CGI) sheets are made by taking sheets of iron, corrugating them for strength, and then applying a protective zinc coating (galvanization) to prevent rust.
Correct Answer: A. Asbestos cement
Solution:
Asbestos Cement (AC) sheets are a composite material made by mixing asbestos fibers into Portland cement. The fibers provide tensile strength to the otherwise brittle cement, creating a durable and fire-resistant roofing material.
Correct Answer: C. Dome
Solution:
A dome is a structural element resembling the hollow upper half of a sphere. It is a type of curved roof known for its ability to span large open spaces without interior supports.
Correct Answer: A. Dovetail halved
Solution:
A dovetail joint is shaped like a fan, which provides strong resistance to being pulled apart (tension). This makes it ideal for connecting the tie beam to the rafters, as the primary force on the joint is tension from the roof spreading.
Correct Answer: D. Trussed roofs
Solution:
This term refers to a more complex roofing system. Single roofs have rafters only. Double roofs add purlins. Triple-membered roofs add a third element, the truss, to support the purlins over large spans.
Correct Answer: A. King rod
Solution:
When a metal rod is used in place of a timber king post to serve the same function (supporting the tie beam), it is referred to as a king rod.
Correct Answer: C. 3 metres
Solution:
The spacing of trusses depends on the loads, the span of the purlins, and the type of wood used. However, a typical spacing for standard wooden roof trusses is around 3 metres.
Correct Answer: A. Two
Solution:
A queen-post truss is characterized by its two vertical members, known as queen posts. They support a straining beam and the tie beam, allowing for a longer span than a king-post truss.
Correct Answer: A. 12 m
Solution:
Queen-post trusses are generally used for spans ranging from about 8 metres to 12 metres. For spans larger than this, more complex trusses or different materials like steel are typically required.
Correct Answer: B. French
Solution:
The mansard roof is named after the 17th-century French architect François Mansart, who popularized its use. It features four sides, each of which has two slopes, the lower one being steeper than the upper one.
Correct Answer: A. Timber and steel
Solution:
Composite trusses combine different materials to take advantage of their unique properties. Typically, timber is used for compression members (like rafters), and steel rods are used for tension members (like the tie beam or king rod).
Correct Answer: D. 15 cm
Solution:
A significant thickness is required for a thatch roof to be waterproof, durable, and provide adequate thermal insulation. 15 cm (or 6 inches) is a common minimum thickness.
Correct Answer: C. Decking
Solution:
Decking, which can be made of metal, wood, or composite material, serves as the structural base of the roof surface. It can be laid at a slope for a pitched roof or nearly flat for a flat roof, with the appropriate waterproof covering applied on top.
Correct Answer: A. 10°
Solution:
While called "flat," these roofs must have a slight slope (or "fall") to allow for proper rainwater drainage. Generally, any roof with a slope of less than 10 degrees is considered a flat roof.
Correct Answer: A. Madras terrace roofing
Solution:
Madras terrace roofing is a traditional flat roofing technique from South India that involves using brick-jelly (broken brick pieces) mixed with lime mortar laid over wooden joists to form a durable, flat roof.
Correct Answer: B. Bhusa (straw)
Solution:
Mud-phuska is a traditional insulating and waterproofing material for flat roofs. Bhusa (chopped straw) is mixed with the clay (mud). The straw acts as a fiber reinforcement, preventing the mud from cracking as it dries.
Correct Answer: D. They can be used as a terrace or roof garden
Solution:
One of the main advantages of a flat roof is that the space can be utilized for other purposes, such as an outdoor patio, a garden, or for placing HVAC equipment. Pitched roofs do not offer this usable space.
Correct Answer: D. Zinc
Solution:
Galvanization is the process of applying a protective zinc coating to steel or iron. The zinc acts as a sacrificial anode, meaning it corrodes before the base metal, thus preventing rust.