This document provides an overview of timber decay and seasoning. It discusses the causes of timber decay and methods to prevent it through proper storage and seasoning. Seasoning involves drying timber to remove excess moisture and is important to improve timber properties for engineering uses. Natural seasoning involves air drying stacked timber, while artificial seasoning uses controlled methods like kiln drying or boiling to dry timber more quickly and uniformly. Proper seasoning improves timber strength, workability, and resistance to cracks, warping and decay.

1. SEMINAR
Basic Civil
Engineering

2. Decay of Timber1
Seasoning of Timber2
Advantages3
Overview

3. DECAY OF TIMBER

4. When timber loses its value as
engineering material, it is said to
be decayed.
The decayed timber cannot be
used for engineering purposes.
Decay of timber

5. Situations favoring early decay of Timber
1) Alternate dry and wet conditions.
2) Bad storage or stacking of timber.
3) Fungus attack.
4) Contact with damp surfaces.
5) Insects.
6) Improper seasoning.
7) Shocks or impacts received during growth.
8) Useage of timber without applying any preservatives.
9) Useage of timber without taking out sapwood from its
structure.
10)Useage of unseasoned wood.

6. Seasoning of Timber
• Fresh timber contains about 50% or more of its own dry
weight as water. The water is to be removed before it
used for engineering purposes. In other words timber
should be dried.
• The process of drying of timber is known as seasoning
of Timber.
• The moisture content should be removed under
controlled conditions at a uniform rate from all parts of
timber.
• Seasoning of timber should be protected from rain and
humidity.

7.  If the drying is irregular, the shrinkage of timber will also
be irregular and it will setup internal stress between fibers.
 Seasoning of timber should be protected from rain and
humidity.

8. OBJECTS OF SEASONING
1. To impart hardness, stiffness, strength and better electrical
resistance to timber.
2. To maintain the shape and size of the components of the timber
articles, which are expected to remain unchanged in form.
3. To decrease the weight of timber and their by to reduce the cost of
transportation.
4. To make timber easily workable and to facilitate operations during
conversions.
5. To make timber suitable for receiving treatment of paints,
preservatives, varnishes etc.
6. To make timber safe from the act of fungi and insects.
7. To make suitable for joinery works.
8. To reduce the tendency of timber to crack, shrink and warp.

9. Free Powerpoint Templates
Page 9
METHODS OF SEASONING
Natural seasoning
Artificial seasoning

10. NATURAL SEASONING
 When seasoning of timber is carried out
by natural air, it is called natural
seasoning or air seasoning.

11.  Timber is cut and sawn into suitable sections of planks or
scantlings.
 The place where stack is to be constructed is cleared and
leveled for good drainage.
 The timber pieces can either be stacked horizontally or
vertically.
The base platform of the stack may be kept 30cm above the
ground level.
The timber pieces are sorted out according to their sizes. They
are stacked in layers one above the other.
The layers are separated by dry pieces of wood of thickness
25mm to 35mm. These spacers may be kept at 450mm to
600mm.
The stack is protected from rain, sunlight and heavy wind.

13. Advantages of natural seasoning
The moisture content of wood can be brought down
to about 10 to 20 percent.
It does not require skilled supervision.
For thicker sections artificial seasoning is
uneconomical where natural seasoning can be
adopted.
This method is cheap and simple.

14. Disadvantages of natural seasoning
1.Less control over air
2.The drying of different surfaces may not be
uniform
3.Chance of attack of fungi and insects during
seasoning.

15. Artificial Seasoning
To make the drying more uniform and even, by
controlled conditions artificial seasoning is adopted.
It reduces the time for seasoning.
Shrinkage, cracking and warping are minimized in
artificial seasoning.
The wood with desired moisture content may be
obtained by the artificial seasoning.

16. 1.Water seasoning
2.Boiling
3.Electrical seasoning
4.Kiln seasoning

17. Water Seasoning
To remove the sapwood, the logs of wood are immersed in
water, preferably in running water of stream and river from 2
to 4 weeks.
Then it is dried under open air . Wrapping and cracking can
be avoided but become brittle and their strength has also
reduced.

18. Boiling
In this method the timber is boiled in water for
about 3 to 4 hours. It is then taken out and slowly
dried. Even though the period of seasoning is less it
is an expensive method.
Timber may be exposed to hot stream also.

19. Electrical Seasoning
This is done by passing high frequency AC current through
the timber. The timber gets heated and dries out.
This method results in uniform seasoning of wood but the
capital cost of equipment needed is more.
It is a very rapid method. This method is used in the
manufacture of plywood.
It is an established fact that a green timber offers less resistance
to the flow of electric current as compared to a dry timber.

20. Chemical Seasoning
In this method, green timber is soaked in
saturated solution of suitable salt and then
removed and seasoned.
 The interior moisture is drawn out by the
saturated salt solution and the interior part dries
before the outer part. Less chance of external
cracks.

21. Kiln Seasoning
In this method timber is carried out inside an air tight chamber.

22. Various process in Kiln seasoning
1) The timber is arranged inside the chamber such that
spaces are left for free air circulation.
2) Humid and heated air of temperature of about 350 C to
380 C is then forced inside a chamber by suitable
arrangement.
3) It is allowed to circulate around the timber pieces.
4) Evaporation from the surface of timber pieces is
prevented because of high humidity of air.

23. 5) The heat gradually reaches inside the timber pieces. The
relative humidity is now gradually reduced.
6) The temperature is then increased and maintained till the
desired degree of moisture content is obtained.
NOTE
Depending upon the mode of construction and operation
Kilns are divided as ,
1. Stationary Kilns
2. Progressive kilns

24. Advantages of Seasoning
1) Handling and transportation cost of wood can be reduced.
2) Seasoned timbre shows good resistance to decay.
3) The timbre should be seasoned before the application of
paints, varnishes, preservatives, glues etc.
4) Ease the workability of timbre.
5) Dimensional stability of furnished products can be maintained.
6) Improved the engineering properties of wood.