cup: a warp across the width of the face, in which the edges are higher or lower than the center of the wood. twist or wind: a distortion in which the two ends do not lie on the same plane. Winding sticks assist in viewing this defect.
The dry rot may be prevented by using well-seasoned timber free from sap. When part of the timber is seriously affected by dry rot, the damaged portion may be completely Removed and the remaining unaffected portion should be painted with a solution of copper sulphate.
Splits and cracks in wood are ruptures or separations in the grain of the wood which reduce the quality as measured by appearance, strength, or utility. Many people assume that all splits and cracks in wood are caused by the dry kiln or the drying operations.
What Does a Lumber Grade Mean? Grades are based on the amount of usable clear material in a board. The highest grade boards are FAS and Select, followed by #1 Common and #2 Common.
Defects due to conversion and seasoning of timber involve shakes, warping, bowing, twist, diamonding, casehardening and honey combing. Some of such important defects are discussed as under. Warping is a kind of variation from a true or plain surface and may include a one or combination of cup, bow, crook and twist.
Common Wood Defects: Types & Causes of Lumber Issues
- Checks and Splits. A check is a term used to describe a crack that runs through a board, usually running lengthwise.
- Rot and Decay. Rot and decay is the general description for the disintegration of wood fiber.
- Ring Shake.
- Pitch, Gum and Sap.
- Wane.
- Crook or Crown.
- Bow.
- Cup.
These three types are: softwoods, hardwoods, and engineered wood. Each of these different wood types can be used in a number of different ways.
In general, hardwood comes from deciduous tree's which lose their leaves annually. Softwood comes from conifer, which usually remains evergreen. The trees from which hardwood is obtained tend to be slower growing, meaning the wood is usually denser.
A knot that has lost its fibrous connection with the surrounding wood; it can easily loosen and fall out or be knocked out.
Right Answer is: DHoney combing: In this type of defect various radial and circular cracks are developed in the interior portion of the timber (resembles honey comb structure) due to stress developed on drying. This defect does not arise due to natural forces.
Wood decay, also known as wood rot, is the decomposition of wood as the result of actions by certain species of fungi.
Wood knots weaken wood strength. In fact, knots materially affect cracking (known is the US as “checksâ€; known in the UK as “shakesâ€), warping, and the ease of working the lumber. They are defects that lower the lumber's value for structural purposes where strength is critical.
Two major methods used for lumber seasoning are air drying and kiln drying.
There are various types of defects in timber as a construction material. These defects in timber can be due to natural forces, fungi, insects, and during seasoning and conversion.
Wet rot is the natural decay of timber due to high moisture levels. Wet rot is caused by a fungus that is attracted to very damp wood and feeds off the timber, destroying it in the process. There are many different types of fungus, but Coniophora puteana, also called cellar fungus, is the most common.
Seasoning is the process of drying timber to remove the bound moisture contained in walls of the wood cells to produce seasoned timber. Seasoning can be achieved in a number of ways, but the aim is to remove water at a uniform rate through the piece to prevent damage to the wood during drying (seasoning degrade).
Defects due to natural forces: The main natural forces responsible for causing defects in timber are two, namely, abnormal growth and rupture of tissues.
A live knot or an intergrown knot is a knot whose growth rings are intergrown with the surrounding wood. A live not is usually lighter in color and will generally never fall out. A dead knot is a knot that has lost its fibrous connection with the surrounding wood; it can easily loosen and fall out or be knocked out.
Definition of WarpingWood that is warped is curved or bent in certain areas from the moisture content being different in specific areas of the wood. This causes some areas to dry faster than others and shrink in size, causing the wood to bend or curve.
