Defects in timber lower its strength, durability, utility, and appearance. Defects are caused by natural forces, insects, conversion processes, seasoning, and fungi. Common defects include knots, shakes, twisted fibers, staining, and rot. Defects are classified based on their origin and impact wood properties and usability. Thorough inspection allows identification and appropriate use of timber despite defects.

1. DEFECTS IN TIMBER

2. DEFINE DEFECTS IN TIMBER
A DEFECT IS AN IRREGULARITY OR ABNORMALITY
OCCURING IN OR ON WOOD WHICH IS RESPONSIBLE
FOR ITS
 STRENGTH REDUCTION
 LOWERING OF DURABILITY
 LOWERING OF UTILITY
 POOR APPEARANCE
 DECAY

3. CLASSFICATION OF DEFECTS
CAUSED DUE TO:
NATURAL FORCES INSECTS
CONVERSION SEASONING FUNGI

4. DEFECTS DUE TO NATURAL FORCES
 CHEMICAL STAIN
 RIND GALLS
 SHAKES
 UPSETS
 TWISTED FIBRES
 KNOTS
 BURLS

5. CHEMICAL STAIN:- THE WOOD IS SOMETIMES
DISCOLOURED BY THE CHEMICAL ACTION CAUSED WITH IT
BY SOME EXTERNAL AGENCY. THIS IS KNOW AS CHEMICAL
STAIN.
RIND GALLS:- THE RIND
MEANS BARK AND GALLS
MEANS ABNORMAL GROWTH.
HENCE PECULIAR CURVED SWELLING FOUND ON THE BODY
OF THE TREE ARE KNOW AS RIND GALLS.THEY DEVELOP AT
POINTS FROM WHERE BRANCHES ARE IMPROPERLY CUT
OFF OR REMOVED.SO THE TIMBER IN THIS PART IS VERY
WEAK AND NOT DURABLE.

6. SHAKES:- THEY ARE THE LONGITUDINAL SEPARATIONS IN
WOOD BETWEEN THE ANNUAL RINGS. THESE ARE THE
CRACKS WHICH PARTLY OR COMPLETELY SEPARATE FIBRES
OF WOOD. THE SEPARATIOON MAKE THE WOOD
UNDESIRABLE WHEN APPERANCE IS IMPORTANT.
TYPES OF SHAKES
 STAR SHAKES
 CUP SHAKES
 HEART SHAKES
 RING SHAKES

7. STAR SHAKES - THESE ARE THE
CRACKS WHICH EXTENDED FROM BARK
TOWARDS THE SAP WOOD. THESE ARE
WIDER AT OUTSIDE ENDS AND
NARROWER AT INSIDE ENDS. THEY ARE
USUALLY FORMED DUE TO EXTREME
HEAT OR SEVERE FROST DURING THE
GROWTH OF THE TREE.
 CUP SHAKE - IT APPERS AS CURVED
SPLIT WHICH PARTLY OR WHOLLY
SEPERATES ANNUAL RINGS FROM
ONE ANOTHER. IT IS CAUSED DUE TO
EXCESSIVE FROST ACTION ON SAP
PRESENT IN THE TREE ESPECIALLY
WHEN THE TREE IS YOUNG.

8. HEART SHAKES - THESE CRACKS OCCUR IN
CENTRE OF CROSS SECTION OF TREE.THESE
CRACKS APPEAR DUE TO SHRINKAGE OF
INTERIOR PART OF TREE WHICH IS
APPROACHING MATURITY. THE HEART SHAKE
DIVIDE THE TREE CROSS SECTION INTO TWO OR
FOUR PARTS.
 RING SHAKE- WHEN CUP SHAKES
COVER THE ENTIRE, THEY ARE KNOWN AS
RING SHAKE.

9. UPSETS:-THESE INDICATE WOOD FIBRES
WHICH ARE INJURED BY CRUSHING OR
COMPRESSION. THE UPSETS ARE MAINLY
DUE TO IMPROPER FEELING OF TREE AND
EXPOSURE OF TREE IN ITS YOUNG AGE TO FAST
BLOWING
WIND.
TWISTED FIBRE:-THESE ARE KNOWN AS WANDERING
HEARTS AND CAUSED BY TWISTING
OF YOUNG TRESS BY FAST BLOWING
WIND. THE TIMBER WITH TWISTED
FIBRES ARE UNSUITABLE FOR SAWING.

10. KNOTS:- THESE ARE THE BASES OF
BRANCHES OR LIMBS WHICH ARE BROKEN OR
CUT OFF FROM TREES. THE PORTION FROM
WHICH THE BRANCH IS REMOVED RECEIVES
NOURISHMENT FROM THE STEM FOR A PRETTY
LONG TIME AND IT ULTIMATELY RESULTS IN
FORMATION OF DARK HARD RINGS WHICH ARE
KNOWN AS KNOTS. AS CONTINUITY OF WOOD
FIBRES ARE BROKEN BYKNOTS, THEY FORM A
SOURCE OF WEAKNESS.
CLASSIFICATION ON SIZE BASIS
 PIN KNOT – DIAMETER UPTO 6.50MM
 SMALL KNOT – DIAMETER UPTO 6.5 AND 20MM
 MEDIUM KNOT – DIAMETER BETWEEN 20 AND 40MM
 LARGE KNOT – DIAMETER GREATER THAN 40MM

11. CLASSIFICATIONON FORM AND QUALITY B
BASIS
 DEAD KNOT- KNOT WHICH IS SEPERATED FROM THE BODY OF WOOD. IT IS
NOT SAFE TO USE WOOD WITH SUCH A KNOT FOR ENGINEERING PURPOSES.
 DECAYED KNOT – POPULARLY KNOWN AS UNSOUND KNOT AND FORM BY
ACTION ON FUNGI ON WOOD.
 LIVE KNOT - IT IS THROUGHLY FIXED IN WOOD AND CANNOT SEPERATED
OUT FROM BODY OF WOOD. IT IS FREE FROM CRACKS AND DECAY . WOOD
CONTAINING THIS KNOT CAN BE USED FOR ENGENEERING PURPOSES.
 LOOSE KNOT- IT IS PRELIMINARY STAGE OF DEAD KNOT.
 ROUND KNOT- THE CROSS SECTION OF THIS TYPE OF KNOT IS EITHER
ROUND OR OVAL
 TIGHT KNOT- IT IS PRELIMINARY STAGE OF LIVE KNOT. THE FIBRES OF KNOT
ARE FIRMLY HELD IN SURROUNDING WOOD.

12. BURLS:- THEY ARE PARTICULARLY
FORMED WHEN A WHEN A TREE RECEIVES
SHOCK OR INJURY IN ITS YOUNG AGE. DUE TO
ITS INJURY, THE GROWTH OF TREE IS
COMPLETELY UPSET AND IRREGULAR
PROJECTIONS APPEAR ON THE BODY OF
TIMBER.
WIND CRACKS:-THESE ARE THE
CRACKS ON THE OUTSIDE OF A LOG
DUE TO THE SHRINKAGE OF EXTERIOR
SURFACE.

13. DEFECTS DUE TO CONVERSION
CHIP MARK
DIAGONAL GRAIN
TORN GRAIN
WANE

14. CHIP MARK:- THIS DEFECT IS
INDICATED BY MARK OR SIGNS PLACED ON
FINISHED SURFACE OF TIMBER. THEY MAY
BE FORMED BY PLANNING MACHINE.
DIAGONAL GRAIN:-THIS DEFECT IS
FORMED DUE TO IMPROPER SAWING OF
TIMBER. IT IS INDICATED BY DIAGONAL
MARKS ON STRAIGHT GRAINED SURFACE
OF TIMBER.

15. TORN GRAIN:- DEFECT CAUSED
WHEN A SMALL DEPRESSION IS FORMED
ON A FINISHED SURFACE OF TIMBER BY
FALLING A TIMBER OR SO.
WANE:- THIS DEFECT IS DENOTED BY
PRESENCE OF ORIGINAL ROUNDED
SURFACE ON MANUFACTURED PART
OF TIMBER.

16. DEFECTS DUE TO SEASONING
TWIST
CUP
BOW
 SPRING

17. TWIST:- WHEN A PIECE OF TIMBER HAS
SPIRALLY DISTORTED ALONG ITS LENGTH, IS
KNOWN AS TWIST.
 CUP:- THIS DEFECT IS INDICATED BY
CURVATURE FORMED IN TRANSVERSE
DIRECTION OF TIMBER.
 BOW:- THIS DEFECT IS INDICATED BY
CURVATURE FORMED IN DIRECTION OF
LENGTH OF TIMBER.
 SPRING:- IS THE CURVATURE OF THE
PIECE OF SAWN TIMBER IN THE PLANE OF
ITS WIDE FACE: KNOWN AS CROOK OR FREE
SIDE BEND.

18. DEFECTS DUE TO FUNGI
BLUE STAIN
BROWN ROT
DRY ROT
HEART ROT
WET ROT
WHITE ROT

19. BLUE STAIN:- THE SAP OF WOOD IS STAINED TO
BLUISH COLOR BY THE ACTION OF CERTAIN TYPE OF
FUNGI.
 BROWN ROT:- THE TERM ROT IS USED TO
INDICATE