---
title: "Queen post truss and its elements"
subject: "Building Technology"
chapter: 4
key: "semester_6/building_technology:queen-post-truss"
source: https://www.bctengineer.com/q/semester_6/building_technology/queen-post-truss
site: BCT Engineering
---

# Queen post truss and its elements

Building Technology · Chapter 4: Roofs

- Asked in: 2076 Baisakh, 4 marks; 2074 Bhadra, 8 marks (asked 2 times)
- Video: [Lec-41_King Post Truss and Queen Post Truss | Building Construction Technology | Civil Engineering](https://www.youtube.com/watch?v=DiZ-9w5YKnU) — Civil Engineering Department_LJIET
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/building_technology/queen-post-truss
- Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-4

## Question

Sketch a queen post truss with its corresponding elements and explain the function of each element.

## Short answer

A queen post truss for 8–12 m spans consists of a tie beam (tension), principal rafters, two queen posts, a straining beam (compression) between them, a straining sill below, and struts to mid-span of rafters. It provides clear space between posts.

## Answer

A **queen post truss** is used for spans of about 8-12 m. It has two vertical **queen posts** instead of one king post, joined at the top by a horizontal **straining beam** and at the bottom by a **straining sill**.

```text
                          ridge
                           /\
                          /  \
                         /    \   principal rafter
     straining beam --> +------+
                       /|      |\
                      / |      | \
                     /  |      |  \
             strut  /\  |      |  /\  strut
                   /  \ |      | /  \
                  /    \|      |/    \
                 +======+======+======+  <- straining sill
                 +--------------------+  <- tie beam
                wall                 wall
       the two vertical members | | are the queen posts
```
| Element | Function |
|---|---|
| Tie beam | Takes the horizontal thrust of the rafters (tension); carries the queen posts |
| Principal rafters | Carry the roof load through purlins; compression and bending |
| Queen posts (2) | Vertical tension members which hold up the tie beam at two points and receive the thrust of the struts at their feet |
| Straining beam | Horizontal strut between the heads of the queen posts; resists the inward thrust of the principal rafters |
| Straining sill | Member on the tie beam between the feet of the queen posts; keeps them apart and resists the thrust of the struts |
| Struts/braces | Inclined members from the feet of the queen posts to the principal rafters; support the rafters midway and reduce their span |
| Purlins and cleats | Purlins carry the common rafters and are held by cleats |
| Common rafters, battens | Directly support the roof covering |
| Wall plate | Spreads the load on the wall |

**Span and use:** spans of 8-12 m for halls, godowns and workshops. Compared with a king post truss it covers a larger span, and the clear space between the queen posts can be used (for example, as an attic or store).

## Check yourself

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

1. Queen post truss span?
   A. 1 m
   B. 20-30 m
   C. 2-3 m
   D. 8-12 m
   Answer: D. Larger than king post. (Key point: Span)

2. Straining beam does?
   A. Covers roof
   B. Carries floor
   C. Strut between queen post heads resisting inward thrust of rafters
   D. Ties feet
   Answer: C. Horizontal strut. (Key point: Straining beam)

3. Straining sill?
   A. Keeps queen posts at fixed distance on tie beam
   B. Rests on ridge
   C. Is a purlin
   D. Is a batten
   Answer: A. Block on tie beam. (Key point: Straining sill)

4. Tie beam?
   A. In compression
   B. Covers
   C. Resists horizontal thrust in tension
   D. Not structural
   Answer: C. Carries queen posts. (Key point: Tie beam)

## Related in Building Technology

- [King post, queen post, mansard trusses; thatch](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aking-queen-mansard-thatch) — Building Technology, chapter 4
- [Single, double, multiple timber roofs; king post truss](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Atimber-roofs-king-post) — Building Technology, chapter 4, asked 2×

## Related in other subjects

- [Truss, beam and frame element differences](https://www.bctengineer.com/question.md?key=semester_8%2Ffinite_element_method%3Atruss-beam-frame-element-differences) — Finite Element Method, chapter 3
- [Bar stiffness matrix and 2D truss element](https://www.bctengineer.com/question.md?key=semester_8%2Fcomputational_techniques_in_civil_engineering%3Abar-stiffness-truss-rotation) — Computational Techniques in Civil Engineering, chapter 4
- [Truss element stiffness matrices](https://www.bctengineer.com/question.md?key=semester_8%2Fcomputational_techniques_in_civil_engineering%3Atruss-element-stiffness-matrices) — Computational Techniques in Civil Engineering, chapter 4
- [Transition elements; non-typical 3d element](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Atm-not-typical) — Engineering Chemistry, chapter 5