--- title: "Uses of roof, types of roof and parts" subject: "Building Technology" chapter: 4 key: "semester_6/building_technology:roof-used-for-types" source: https://www.bctengineer.com/q/semester_6/building_technology/roof-used-for-types site: BCT Engineering --- # Uses of roof, types of roof and parts Building Technology · Chapter 4: Roofs - Asked in: 2071 Bhadra, 8 marks - Video: [Types of Roof | Building Construction | Civil Engineering](https://www.youtube.com/watch?v=OT9MP104iXY) — SGK Online Education - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_6/building_technology/roof-used-for-types - Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-4 ## Question What is roof used for? Sketch out different types of roof and show their parts. ## Short answer Roofs protect from rain, sun, wind, provide privacy, support services, and create extra space. Types: flat (slope ≤10°), pitched (slope >10°: lean-to, gable, hip, gambrel, mansard, etc.), curved (shell, dome, vault), and combination. Pitched roof parts: ridge, hips/valleys, eaves, rafters, purlins, battens, tie beam, wall plate, covering. Flat roof parts: RCC slab, screed, waterproofing, finishing, parapet, rainwater pipes. ## Answer #### Uses of a roof A roof protects people and property from rain, snow, sun, heat and wind, gives privacy and security, supports services (tanks, solar panels), and provides extra space (terrace, attic). #### Types of roof with parts Roofs are classified as: 1. **Flat roofs:** nearly horizontal (slope up to 10 degrees, about 1 in 40 to 1 in 60 for drainage); RCC or stone slab, jack-arch and terrace roofs. 2. **Pitched (sloping) roofs:** slope more than 10 degrees; covered with tiles, slates, sheets or thatch over timber or steel frames. Types: lean-to, gable (couple), hip, gambrel, mansard, hip-and-valley, north-light, butterfly, conical. 3. **Curved (shell) roofs:** shell, dome, vault, barrel and folded plate roofs for large halls. 4. **Combination roofs:** part flat and part pitched on the same building (for example, a flat RCC terrace with a sloping tiled or sheet roof over one part). ```text Lean-to Gable (couple) Hip /| /\ /--\ / | / \ / \ /__| /____\ /______\ Mansard North light ____ /| /| /| / \ / | / | / | / \ /__|/__|/__| | | ``` #### Parts of a pitched roof ```text ridge /\ / \ <- rafter rise -> / \ / \ eaves ->_/________\_<- eaves wall plate wall |<-- span -->| ``` Main parts: ridge (the top line where the slopes meet), hips and valleys (the inclined external and internal angles), eaves (the lower overhanging edge), rafters (the inclined supports), purlins (the horizontal supports under the rafters), battens, tie beam, wall plate and the roof covering. For a **flat roof** the parts are: RCC slab, screed (brick bat coba or lean concrete) to give the slope, waterproofing layer, finishing (tiles), parapet wall with coping, and rainwater pipes (RWP). ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which is NOT a main class of roof in the answer? A. Suspended cable roofs B. Flat roofs C. Pitched roofs D. Curved (shell) roofs Answer: A. Classes are flat, pitched, curved (shell) and combinations. (Key point: Roof classes) 2. Flat roofs have slope up to about what? A. 30 degrees B. 10 degrees, about 1 in 40 to 1 in 60 for drainage C. 45 degrees D. 60 degrees Answer: B. Flat roofs are nearly horizontal with a small drainage slope. (Key point: Flat slope) 3. What are the eaves? A. The top line where slopes meet B. Horizontal supports under rafters C. The lower overhanging edge of the roof D. The tie joining rafter feet Answer: C. Ridge is the top; eaves are the lower overhanging edge. (Key point: Eaves) 4. Which is a part of a flat roof? A. Purlins and rafters B. King post C. Collar beam D. Waterproofing layer over a screed laid to slope Answer: D. A flat roof has an RCC slab, screed, waterproofing, finish, parapet and RWP. 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