Timber is wood that is used as building material for the construction of buildings and other structures. Depending on the shape and degree of processing distinction is made between different timber products, which are classified into the categories of solid wood, laminated wood and wood-based materials. Various standards define quality standards and qualifications that must meet the timber products, depending on the use.
Higher quality quality classes are partially discriminated as a so-called construction timber from the timber.
Wood is suitable for many reasons well as building material, for example because of the low density combined with high stiffness, good processability, stability ( durability), carrying capacity, etc. These properties depend strongly on the type of wood, the wood proportions used ( heartwood, sapwood ), the processing, wood preservation, and many other factors.
Various standards help ensure certain qualities in the timber. In Germany in 1052, only certain types of wood to use for load-bearing applications are eg according to DIN approved:
- Conifers: spruce, fir, pine, larch, Douglas fir, Western Hemlock, Southern Pine and Yellow Cedar.
- Hardwoods: Oak, Beech, Teak, Keruing, Afzelia, Merbau, Angélique ( Basralocus ) Bongossi and Greenheart.
The processing of timber in the construction industry is in the area of the shell (construction and repair of roofs, construction and installation of prefabricated houses, repair and construction of timber-framed houses, etc.) instead. These activities fall within the scope of the carpenters.
In construction, more wood products are used, but not part of the timber in the proper sense. These are, for example, windows, doors and parquet. Also in concrete construction wood is often used for auxiliary structures, eg as forms, but which is also not counted for lumber.
As solid wood or solid wood timber products are called, worked out the cross-sections of a tree trunk and possibly machined (drilling, milling, planing, etc.) have been processed. The structure of the wood, unlike laminated wood and wood materials, not altered or mechanically - chemically.
When solid wood is made between roundwood and sawn timber:
Building Logs consists of delimbed, debarked or roughly peeled tree trunks or trunk sections, referred to as roundwood. These are often used without further processing as stake / peg, such as posts or columns, driven pile (Pilot), masts, palisades, for the construction of playground equipment as well as in hydraulic engineering, eg as dolphins.
Quality Requirements for Building Logs are defined in DIN 4074 Part 2 timber to timber members; Quality Conditions for Building Logs. ( Softwood ) defined.
Timber is made of round wood by sawing parallel to the stem axis, has a minimum thickness of 6 mm and usually a rectangular or approximately rectangular cross section. It can be cut with sharp edges or still have remnants of the contour tree trunk.
Prerequisite for use as lumber for load-bearing purposes, such as roof trusses, is sorting by the resistance according to DIN 4074 (Part 1 of softwood lumber or Part 5 for hardwood lumber ). Sorting by the Tegernsee usages formerly often used is no longer relevant for timber, but still commercially available. The DIN 4074 was admitted as a product standard in the Building Regulations List and is introduced by the building. Lumber for structural purposes must therefore necessarily correspond to the sorting criteria of this standard.
As construction timber refined timber is called, which according to an Association Agreement between the Association of German Master Carpenters and monitoring Konstruktionsvollholz compared to DIN 4074 met increased quality requirements. It consists of coniferous solid wood timbers of wood species pine, fir, larch, Douglas fir or spruce. It is further distinguished between structural timber for the visible range ( KVH -Si) and construction timber for the invisible area ( KVH - NSi ). In general, KVH is a finger-jointed solid wood product made of softwood. Thus, arbitrarily long lengths can be produced. According to EN 1995-1-1, Section 3.2, para 5 shall comply with the requirements of DIN EN 385 finger joints. According to DIN EN 1995-1-1/NA, NCL to 3.2 Finger-jointed solid wood may only be used in service classes 1 and 2. The service classes are defined in DIN EN 1995-1-1, Section 18.104.22.168. For KVH the strength, stiffness and Rohdichtekennwerte for solid wood apply. The values are given in DIN EN 338.
Depending on the cross -sectional shape and dimension timber is divided into different product classes according to DIN 4074-1:
When timbers are called timber, which is provided by fogging ( forms of the square timber by ax ) or sawing with four mutually at right angles to edges which give the cross-sectional area. Squares are used both in the construction industry, as well as in the cabinet making. Where they are used as table legs, braces, backrest and much more. As lumber timbers have a minimum thickness of 4 cm according to DIN 4074 lumber (or 6 cm DIN 68252 for trading goods in general), the cross-sectional height is three times the maximum width. Mostly edgewise bending stressed boards and planks are to be sorted according to DIN 4074-1 as timber and be labeled accordingly. Important areas of timbers are or were, for example, rafters, columns, and truss.
The bar is the commonly used form for the technical designation of a square timber, which refers more or less to the type of application / use or dimension. At the bar the longer side of the cross section measuring less than 20 cm. Often bars are used for the construction of wood -beamed ceilings.
Beam can be made of solid wood products or can, machine-made of two or three flat sides, parallel to the fibers bonded together planks or timbers exist. Duobalken ® and Trio ® bars are called bars plywood. The names of laminated wood, glued beams, glulam, glulam should be avoided because of the risk of confusion with other products. Glued laminated wood may DIN EN 1995-1-1/NA, Section NCL NA.3.8, para NA.2 be used only in service classes 1 and 2 and requires under paragraph NA.1 a general building inspectorate approval. According to approval Z -9.1 -440 With the exception of modulus of elasticity parallel to the grain are the strength, stiffness and Rohdichtekennwerte for solid wood.
As a lumber pile has a minimum thickness of 40 mm and a width of at least three times the thickness.
A board having a maximum thickness of 40 mm and a width of at least 80 mm. Boards for the manufacture of glulam, larger thicknesses than 40 mm.
A latte is also thick to 40 mm, but in contrast to the board a maximum width of 80 mm.
With glulam larger dimensions, freer forms and higher strengths than with solid wood can be achieved. The inherent limitations of the dimensions to be overcome, and it can also be carried out wide-span engineering structures ( Wood Engineering ), which are economically and structurally competitive with steel and prestressed concrete.
Wood-based materials are materials, which are produced by grinding wood and subsequent joining of the structural elements. Examples are plywood, wood chip materials ( chipboard, OSB ) or wood fiber materials ( hardboard, MDF ).
For timber different standards ( DIN Standard ( DIN) and European Standard ( EN ) ) are relevant:
- DIN 1052:2008-12 Calculation and Design of timber structures - General rules and rules for buildings.
- DIN EN 1995-1-1:2010-12 Conforms to European standard EC5 and has the status of a German standard and is only in conjunction with the national application document DIN EN 1995-1-1/NA :2010 -12 valid. The DIN EN 1995-1-1 is probably introduced by mid-2012 alone valid and thus replaces the DIN 1052:2008-12
- ÖNORM B 1995-1-1 ( 2004/A1: 2008) / NA: 2009 EC 5, Conforms to European standard and has the status of an Austrian standard. The National Annex (NA ) is introduced by the building (6/ 2009) and must be used in Austria.
- DIN 4074: DIN 4074-1 ( 2003-06 ) classification of wood after load - Part 1: Coniferous sawn timber.
- DIN 4074-2 ( 1958-12 ) timber to timber members; Quality Conditions for Building Logs (coniferous wood).
- DIN 4074-5 ( 2003-06 ) classification of wood after load - Part 5: hardwood lumber. is also binding as ÖNORM DIN 4074 -x for Austria