---
title: "Methods of seasoning timber"
subject: "Civil Engineering Materials"
chapter: 7
key: "semester_3/civil_engineering_materials:methods-of-seasoning-timber"
source: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/methods-of-seasoning-timber
site: BCT Engineering
---

# Methods of seasoning timber

Civil Engineering Materials · Chapter 7: Timber

- Asked in: 2080 Baisakh, 3 marks; 2057 Chaitra (old course), 8 marks (asked 2 times)
- Video: [Seasoning of timber types of seasoning](https://www.youtube.com/watch?v=veD-xtLdDpU) — Architects Academy
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/methods-of-seasoning-timber
- Whole chapter: https://www.bctengineer.com/md/semester_3/civil_engineering_materials/chapter-7

## Question

Explain the various methods of seasoning of timber, with sketches where needed.

## Short answer

Seasoning removes moisture to 10–15%. Natural methods are air drying (stacked with spacers under cover for months) and water seasoning (submerged, then dried). Artificial methods like kiln drying use controlled hot air for fast, uniform drying in days.

## Answer

**Seasoning** is the controlled removal of moisture from timber to bring its moisture content to 10-15%. The methods are classified as natural and artificial.

#### A. Natural seasoning
**1. Air seasoning:** logs are cut into planks and stacked in a shed, well ventilated and protected from sun, rain and wind.
```text
     (shade roof)
   ===================
   --- boards ---        <- sticker (spacer)
   --- boards ---        <- sticker
   --- boards ---
   ___ ___ ___ ___ ___   <- raised platform
   |  |  |  |  |  |       (300 mm above ground)
```
- Planks are piled on raised platforms with spacers (stickers) of 25 mm so air circulates.
- It takes 6 months to 2-3 years. It is slow but cheap and gives a uniform result.

**2. Water seasoning:** logs are submerged in running water for 2-4 weeks, with the thick end facing upstream. The sap is washed away, then the logs are dried in air. It is quick and reduces shrinkage, but may weaken the timber.

#### B. Artificial seasoning
**1. Kiln seasoning:** timber is stacked in a closed chamber (kiln) in which hot air with controlled humidity and temperature circulates. Temperature is raised in stages (about 35 C to 80 C) with humidity reduced slowly. Done in 4-10 days (depends on thickness). Controlled, fast, but costly.
```text
   Hot air in -> [ stacked timber ] -> moist air out
        ^                                  |
        +----- Fan, heater, steam sprays --+
```
**2. Chemical (salt) seasoning:** timber is soaked in a solution of urea or common salt, which draws moisture from the inner part and slows down surface drying, which reduces cracking.
**3. Electrical seasoning:** a high frequency current passes through the timber and heats it; very fast but costly (used in special cases).
**4. Boiling:** timber is boiled in water, then dried in air.
**5. Smoke seasoning** for small items is used in rural areas.

#### Comparison
| Natural | Artificial |
|---|---|
| Slow (months-years) | Fast (days) |
| Cheap, no equipment | Costly, needs plant |
| Less control, defects possible | Controlled, uniform |

## Check yourself

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

1. In air seasoning, planks are stacked
   A. Directly on the ground in sun
   B. Under running water
   C. In closed hot chambers
   D. On raised platforms under a ventilated shed with spacers
   Answer: D. Raised, shaded, ventilated stacking. (Key point: Air seasoning)

2. In water seasoning the logs are
   A. Immersed in running water 2-4 weeks, thick end upstream, to wash out sap
   B. Boiled in oil
   C. Stacked in a kiln
   D. Soaked in still saltwater for years
   Answer: A. Sap is washed out. (Key point: Water seasoning)

3. Kiln seasoning is characterised by
   A. Slow drying over years
   B. Controlled temperature and humidity, fast (4-10 days) but costly
   C. No equipment needed
   D. High frequency current
   Answer: B. Kiln is controlled and fast. (Key point: Kiln seasoning)

4. Why is timber soaked in urea or salt in chemical seasoning?
   A. It heats the wood
   B. It kills fungi only
   C. It draws moisture from the inner part and slows surface drying, reducing cracking
   D. It colours the wood
   Answer: C. Salt equalises the drying rate. (Key point: Chemical seasoning)

## Related in Civil Engineering Materials

- [Seasoning of timber and its necessity](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Aseasoning-meaning-necessity) — Civil Engineering Materials, chapter 7, asked 8×
- [Why timber is used; seasoning method](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Aseasoning-method-and-timber-use) — Civil Engineering Materials, chapter 7
- [Natural versus artificial seasoning](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Anatural-artificial-seasoning) — Civil Engineering Materials, chapter 7
- [Defects caused by seasoning](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Aseasoning-defects-timber) — Civil Engineering Materials, chapter 7
- [Define seasoning, need, methods](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Aseasoning-defined-seasoning-s) — Civil Engineering Materials, chapter 7
- [Uses of timber and modified timber](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Auses-of-timber-modified-timber) — Civil Engineering Materials, chapter 7

## Related in other subjects

- [Collar timber roof](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Acollar-roof) — Building Technology, chapter 4
- [Simple timber beam and flitched beam](https://www.bctengineer.com/question.md?key=semester_6%2Fdesign_of_steel_and_timber_structure%3Asimple-flitched-beam-sketch) — Design of Steel and Timber Structure, chapter 12