---
title: "Couple close roof sketch"
subject: "Building Technology"
chapter: 4
key: "semester_6/building_technology:couple-close-roof"
source: https://www.bctengineer.com/q/semester_6/building_technology/couple-close-roof
site: BCT Engineering
---

# Couple close roof sketch

Building Technology · Chapter 4: Roofs

- Asked in: 2072 Magh, 5 marks
- Video: [Closed Couple roof](https://www.youtube.com/watch?v=XaoO3KN8xsM) — Architects Academy
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/building_technology/couple-close-roof
- Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-4

## Question

Describe couple (couple close) roof with necessary sketches.

## Short answer

A couple-close roof pairs rafters meeting at the ridge; a horizontal tie beam at their feet takes horizontal thrust, sending only vertical loads to walls. Spans up to 4.5–5 m, simple, but rafters may sag beyond that.

## Answer

In a simple **couple roof**, pairs of rafters meet at the ridge and rest on wall plates without any tie, so they push the walls outward (span about 3.6 m). Adding a tie at the feet of each pair gives the couple-close roof.

A **couple-close roof** is a single roof in which each pair of common rafters meeting at the ridge has its feet connected by a horizontal **tie beam**. The tie takes the horizontal thrust, so only vertical loads reach the walls. Span about 4.5-5 m.

```text
          ridge
           /\
          /  \ rafters
         /    \
        /      \
     __/________\__
    wall plate  tie beam  (wall plate)
```
Features:
- Rafters about 50 x 100 mm to 50 x 125 mm at 400-600 mm c/c, ridge piece 40 mm thick; tie beam 50 x 100 mm or more.
- Rafters are notched/spiked to the wall plate and tie.
- Advantage: no outward thrust, simple. Limitation: the rafters sag if the span exceeds 5 m, so a collar roof or double roof is used.
- Used for small houses, sheds and verandahs.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Tie beam function?
   A. Supports ridge
   B. Prevents leaks
   C. Carries covering
   D. Takes horizontal thrust so only vertical loads reach walls
   Answer: D. Removes outward thrust. (Key point: Tie function)

2. Span of couple close?
   A. 12 m
   B. 4.5-5 m
   C. 1 m
   D. 20 m
   Answer: B. Small spans. (Key point: Span)

3. Limitation?
   A. Heavy
   B. Thrust
   C. Rafters sag beyond 5 m
   D. Costly
   Answer: C. Use collar or double roof. (Key point: Limitation)

4. Used for?
   A. Bridges
   B. Halls
   C. Small houses, sheds, verandahs
   D. Factories
   Answer: C. Small buildings. (Key point: Use)

## Related in Building Technology

- [Couple closed roof and mansard roof truss](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Acouple-closed-mansard) — Building Technology, chapter 4
- [Couple closed roof versus collar roof](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Acouple-vs-collar) — Building Technology, chapter 4, asked 2×
- [Requirements of roof; coupled roof](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aroof-requirements-coupled) — Building Technology, chapter 4
- [Why joints are necessary; expansion joint](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Ajoints-why-expansion) — Building Technology, chapter 10, asked 2×
- [Requirements of good roof; pitched roof types](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aroof-requirements-pitch-066j) — Building Technology, chapter 4
- [Roof types, functional requirements, timber roofs](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aroof-types-requirements-timber) — Building Technology, chapter 4, asked 5×

## Related in other subjects

- [D'Alembert's principle; gears with couple](https://www.bctengineer.com/question.md?key=semester_3%2Fapplied_mechanics_dynamics%3Adalembert-gear-a-b-couple-8nm) — Applied Mechanics (Dynamics), chapter 5
- [Cross drainage: Q 25, uplift on roof of barrel](https://www.bctengineer.com/question.md?key=semester_6%2Firrigation_and_drainage_engineering%3Acd-q25-uplift-roof-barrel-800) — Irrigation and Drainage Engineering, chapter 8, asked 2×