different types and species of structural timber pdf Thursday, April 29, 2021 10:13:53 AM

Different Types And Species Of Structural Timber Pdf

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This guide describes timber strength groups and their relationship with the stress grades specified for structural applications. Use the quick reference tool to determine the minimum strength group required to meet a specified stress grade. Stress grades table.

For further information, visit www. For structural purposes movement is not usually significant, but if you require stability in varying humidities e. These classifications are not directly related to the shrinkage of green timber. Refers to resistance to fungal decay of the heartwood only. Sapwood in most species is generally not durable and should not be used in exposed conditions without preservative treatment.

Timber Structures

For further information, visit www. For structural purposes movement is not usually significant, but if you require stability in varying humidities e. These classifications are not directly related to the shrinkage of green timber. Refers to resistance to fungal decay of the heartwood only. Sapwood in most species is generally not durable and should not be used in exposed conditions without preservative treatment.

Classes referred to in BS EN are:. Refers to how easily timbers can be penetrated with vacuum pressure preservative treatments. Wood Campus Timber Trade Topic sheets are designed for builders and the wider timber trade. This Topic sheet provides general advice only and is not specific to the requirements of a particular building project. Care has been taken to ensure the information is accurate and up-to-date. However, neither Wood Campus, nor any of its collaborators, can be held responsible for any mistakes or omissions.

Does it have the right strength qualities? How durable is it? What does it look like? Will it last? Are there legal and sustainable supplies? What are the main types of timber species? Softwoods Softwood timber is obtained from conifers — trees with needle-like leaves, usually bearing cones.

Softwoods are the most commonly-used timber because they offer good value and are readily available from sustainably-managed forests. They are less dense and easier to work with than most hardwoods. Of the species of softwoods throughout the world, around 50 are in commercial use, with the most common being European Redwood and Whitewood pine and spruce. Hardwoods Hardwoods are mainly broadleaf, deciduous trees, shedding their leaves in winter, although some hardwoods are evergreen.

There are two groups, temperate and tropical, accounting for some 20, different commercial species. Although generally more durable and stronger than softwood, they must be used in the correct way and environment. The majority of hardwoods are deeper in colour and have a higher density than softwood, due to their cellular structure. However, some hardwoods, particularly tropical species, grow fast enough to be of similar, or lower, density than slow growing softwoods.

Hardwoods are usually supplied in random lengths and widths, but in standard thicknesses are often used as veneers on softwood. Illegal trade in tropical hardwoods has been largely responsible for deforestation.

Care should be taken to ensure you are supplied with timber from legal and sustainable sources. Which species of wood should I choose? Consider these points: The end use — for example, is the wood to be used as a structural material and then covered with something else, i.

What strength is required? Does the timber need to have a high bending strength, such as a joist, or a high tensile strength where the timber is stretched in the application? Is the wood to be used purely for a decorative effect?

Is this to be a dark or light colour? Is the wood to be machined? Some species are more easily machined than others. Is the wood from a certified legal and sustainably-managed forest source i. Verified Progress? It may look nice, but is it worth the additional cost, if another less expensive and more commercially available timber can do the same job?

Durability and treatability: is it necessary to use preservatives? Africa Yellowish brown Medium to coarse Medium Medium to difficult Durable Extremely difficult Furniture, interior and exterior joinery, flooring, heavy structural.

Africa Yellow brown Medium Small Medium to difficult Durable to very durable Extremely difficult interior and exterior joinery, bridge construction Sapele W. Africa Reddish brown Medium Medium Medium Moderately durable to durable Extremely difficult Interior and exterior joinery, furniture, cabinet work. Generally, these products provide the sustainability of softwoods with the stability and durability normally associated with hardwoods.

The different modification processes affect the performance of the timbers in different ways. Consult the manufacturer for specific details.

Tannin stain Tannin is natural in softwoods and hardwoods. For example, oak and Western red cedar will exude tannin as they dry, which may give the appearance of a black deposit. As a result, water running off these surfaces can leave staining, particularly around metal fixings. Available species Consult your local timber merchant or Timber Trade Federation member www.

Swedish grown species www. UK grown species www. American species americansoftwoods. Technical information www. Sustainable timber Timber is the most sustainable mainstream building product.

It is naturally renewable. Softwood and temperate hardwood forests in Scandinavia, Europe, Canada and North America are stable or growing. Growing forests act as carbon sinks; wood products act as carbon stores. Click the icon to download the pdf version. Privacy Policy Cookie Policy.

Strength groups and stress grades

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Earthquake design ; Earthquake resistance ; Timber buildings ; Wood ; Wood buildings ; Wood products. This became more desirable as settlements increased in size and buildings were built closer together. This increases the risk of rapid fire spread between closely spaced buildings with timber claddings and thatch or other combustible roofs. Prior to the advent of modern fire fighting equipment and organizations, and automatic suppression systems in the late nineteenth century, noncombustible materials were the only way of preventing fire spread between and within buildings.

Structural grading is the process by which timber is sorted into groups - or stress grades - with ideally, similar structural properties in each group. Inevitably there is a very substantial range of properties within a group and significant overlap in properties between the groups. Structural grading can be performed in a number of ways including the following:. The two most commonly used methods in Australia are visual stress-grading and machine stress-grading, with use of machine proof-grading being limited. In theory, any method that sorts timber into groups of material with similar structural properties could be used.

Timber is a type of wood which has been processed into beams and planks. Basically, timber or Lumber is a wood or firewood of growing trees. Any wood capable of yielding a minimum dimensional size can be termed as a timber or lumber. It is a stage in the process of wood production.

A worked example is also provided. It has been my experience to never use a beam smaller than a two ply 2 x 8. The essential design values have been established for a wood with moisture content of nineteen percent or smaller.

Timber as a Structural Material 1.1 INTRODUCTION

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