Causes of timber defects

The defects occurring in the timber are grouped into the following five divisions. In his research work, chew 2005 identified that among the various causes of defects in timber, poor seasoning methods accounted for about 40% which leads to a considerable amount of moisture content in the timber. Cupping, which is warp across the width of lumber, is a natural event for wood, with the bark side of lumber shrinking more than the. In the process of converting timber to commercial sizes and shapes the following types of defects are likely to airse. But in this post we are going to discuss about defects in timber, various defects in timber, causes of timber defects etc. Defects in timber are generally distinguished as natural defects and artificial defects. The curvature of a piece of sawn timber in the direction of its length, cf. The attack of timber by fungi when moisture content of timber is above 20% and presence of air and warmth for the growth of fungi the following defects are caused.

Timber defects a natural material with minimal processing in order to make it a usable product in house building. Soft tissue or skin which covers the wound of tree. Types of defects in timber as a construction material. A knot marks the position of growth of a branch on the tree. Warping can also occur in wood considered dry wood can take up and release moisture indefinitely, when it takes up moisture unevenly, or especially is allowed to return to its dry equilibrium state unevenly, too slowly, or too quickly. It is also essential to use some recommended details to better manage the defects and implement necessary remedial actions. Various causes are suggested, such as felling across obstructions, and failure inside the growing tree caused by high winds, growth stresses, etc. Timber is a natural product so natural variations in grain, color, checking, are to be expected. These occur where branches have grown out of the tree trunk. Shakes, checks and splits in dimension lumber spib blog. Decay or disease of timber by removal of cellulose compounds from wood and wood assumes the.

But unfortunately timber usually possess different types of defects. The environmental approach to the eradication of fungal decay relies heavily on the removal of the causes of damp. A few of the main causes for birth defects include any bad habits such as smoking, drinking alcohol, and doing any kind of narcotic. Ppt defects in timber powerpoint presentation free to. This defects is due to separation of the tissues in the interior of timber due to drying stresses, caused by incorrect kiln seasoning as the interior wood dries earlier than the external surface. This type of defect is due to excessive compression in the tree when it was young. A most commonly observed defect in timber are knots. Since some defects are not observed in green lumber and are first noted after the drying operation, they are often called drying defects even though the defects may have started in the tree, log, or green lumber. Sep 25, 2010 the defect caused by these insects may occur in heartwood as well as in sapwood. It rarely extends through the beam to the other side, and is accounted for in engineering calculations.

The heart is the center of the bullseye on a log before it is squared up into a timber beam. Home inspection 10 common defects of flooring to spot. Timber defects are imperfections that occur naturally or commercially. Designers, contractors and site supervisory staff should understand the common defects and their related causes to prevent them. Movie created by first year industrial design students at cput. Branches near the earth or lower branches are dying when a tree is growing. Knots are the most common defects caused due to natural forces. A distortion due to differential shrinkage in drying that causes a piece of timber originally square or rectangular in cross section to become diamondshaped. Aug 15, 2019 this defects is due to separation of the tissues in the interior of timber due to drying stresses, caused by incorrect kiln seasoning as the interior wood dries earlier than the external surface.

The machining process to produce dimensional lumber puts a large amount of stress on wood. It is used as building structural element as well as door, window, partition etc. Defects in lumber are faults that detract from the appearance and utility of the wood. Building defects and failure of malay timber house. The roots of these branches remain in the trees as the trees gro. Types of defects in timber or timber defects civil. One of the biggest challenges of working with timber is learning to work within the constraints of a timbers. Wet rot is caused by fungi which decomposes the timber and converts it into grayish brown powder form. Causes of timber defects causes of timber defects are divided into the following classes. Identifying hardwood defects part one while volume is the single most important factor in determining the value of a stand of timber, the quality of the trees is nearly as important.

In all drying defects, end splits, surface checks, and end checking or splitting the rupture will extend across one or more growth rings. Wood treatment methods timber treatment how to treat wood. This defect occurs when the rays pass through diagonal corners of the square or rectangle and is caused by the difference between tangential and radial shrinkage which in many timbers is in the proportion of about 2. When the converted timber is stored for longer time, some timber planks may have curve along its length which is known as bow. Knots a most commonly observed defect in timber are knots. These defects are typically grouped into three categories. Deterioration of timber thermal insulation northern. A defect is simply an abnormality or irregularity found in wood. Once any timber decay repair work has been completed, it is recommended that you install an electronic system to monitor the moisture content in and around the problem areas of your home. It takes the form of numerous circular holes or short tunnels of 15018 in. Some are present when the wood is produced and others develop or become more severe as the wood ages. When the moisture content in the timber is more than 25%, some types of fungi attacks the sap wood and makes it discolored. Wet rot causing fungi growths mainly when there is.

The various types of defects under each category will now be briefly discussed. When this is cut through during conversion the result is a. This can put the person and baby at risk for intense problems before, during, and after birth. Defects may be natural which occur whilst the tree is growing, or artificial as a result of poor conversion, seasoning or handling after felling. The main natural forces responsible for causing defects in timber are. Some of the most common are knots, compression creases, pitch pockets, and waney edges. Defects in timber causes of timber defects expert civil. Some are caused during the growth of the tree while others are caused as a result of poor seasoning and conversion methods.

Defects in timber we had already discussed about what is timber and common timbers in india. What are the main causes of timber defects answers. Shrinkage on aging of the tree due to movement caused by wind action in the. The roots of these branches remain in the trees as the trees grow. The following are a list of the most common wood defects. Natural defects include knots, weakshort grain, sap pockets etc. Guide the carrier along the tablesaw fence to rip off one bad edge. As a general rule, you can reduce the amount of defects by purchasing highergrade materials at the outset. There are various types and reasons of defects in timbers and woods.

Double vacuum, low pressure treatments can be used for building and joinery timbers in use classes 1, 2 and 3. Typically timber decay may occur at roof timber, floor timber and joinery timber such as door frame or window frame figure 6 and figure 7. During the growth of a tree, branches close to the. Treatment provides an effective envelope protection around the timber and leaves the colour of the timber virtually unchanged. Fungal damage fungi generally damages timber or wood by. Shakes, checks and splits and the grade of dimension lumber a relatively small amount of splits, checks, or shakes are acceptable under the grading rules for dimension lumber and the amount allowed varies. The readytouse material is easy to use and the flooring repaired by matching the tonality of the wood. Timber may in certain circumstances be attacked by various woodboring insects, which differ in their choice of species and condition of the wood from standing trees to woodwork which has been in service for many years. Types of defects in timber are grouped into the following divisions.

Dealing with wood defects to put a straight edge on a crooked board, stick it on a long, straight carrier, such as a strip of plywood about 34x8x60, using doublefaced tape. Perfect timber logs would make the construction work simple. In trying to reshape a large uneven log composed of complicated grain patterns into usable lumber can cause reactions that produce lowquality lumber. Defects caused to timber by insects and marine borers. If seasoning is not uniform, the converted timber may warp and twist in various. There are innate defects caused by the natural characteristic of wood to shrink. Irregular projections appear on the body of timber because of shock at younger age. These are defects found in lumber that are caused by sawing and dressing lumber. Common defects that occur in timber include knots, shakes, wind cracks, upsets, twisting, cupping, bowing, rot and insect damage. Mar 06, 2018 on finding these defects we of course had serious concerns as to what effect this long term water ingress was having on the timber frame. They may reduce strength and increase difficulty working the timber but are mainly a visual defect indeed, knotty pine is used to decorative. On the basis that fungal attack will cease when timber is at less than 20% moisture content, increased ventilation and the rectification of building defects should prevent further attack.

Timber is far from being a stable and consistent material. Defects caused to timber by insects and marine borers hubpages. Checking is cracking that develops along the radius of a log. Its subject to defects from the time it emerges as a seedling to the last stages of seasoning. Where a branch has grown out of a tree the grain in the trunk becomes very twisted. Knots can add to the appearence of certain projects. Caused chemical decomposition of wood of the timber and. Not all defects take away from the appearance of wood like knots.

Shakes are nothing but cracks which separates the wood fibers partly. Branch propagation shows up as knots in the wood,the nature of the species of tree,and the location conditions, insects and diseases. On checking the timber moisture content to the head of the timber frame we recorded a moisture content of 21. When fungi feed only on sapwood, where the food materials are stored, it causes a stain. If the wood is exposed continuously to the highspeed winds. Defects due to conversion and seasoning defects due to fungi defects. The defect is due to the corrugates appearance of timber, caused due to excessive and uneven shrinkage during drying. During the process of converting timber to commercial form, the following defects may occur.

The aim of remedial building works is to control the timber decay, to prevent further decay and to correct any significant building defects resulting in conditions of high moisture content or poor ventilation of timber. It occurs around the growth rings of a timber and is often found in older trees that grow in wet. Defects in timber doors and windows the weathered bottom half of a wooden door variations in the colour, texture or grain pattern of the wood should not be considered as defects, as they are a natural feature of. Wood warping is a deviation from flatness in timber as a result of stresses and uneven shrinkage. Following pdf files regarding defects in timber are published in different websites. Defects on timber due to poor seasoning and conversion. Defects in wood common defects and characteristics found in wood. On the cut board, it is most easily marked by its conspicuously darker. To this end, a number of factors can cause trees to have defects, and therefore lower values. Live knots are fully integrated with the surrounding timber. Wood is a natural material, exposed to differing and unpredictable conditions as it grows, wood often develops features which are undesirable to the woodworker. Defects in timber may be defined as, any undesirable character natural or artificial that lowers its strength, durability or quality. Fohc free of heart center timber typically has less checking than boxed heart timber.