Faq
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Everything you need to know about BauBuche – from A for applications to V for vapour barrier.
Material properties
BauBuche is shipped with a moisture content of 6% (+/- 2%). For production reasons, delivery with a higher wood moisture content is not possible.
The compressive strength of BauBuche in service class 1 is 20% higher than in service class 2. Both values are specified in the technical approval (ETA-14/0354). Service class 1 is characterised by a moisture content in the wood corresponding to a temperature of 20°C and applications where the relative humidity of the surrounding air exceeds 65% only for a few weeks per year. The average wood moisture content is maximum 12%. Service class 2 is characterised by a moisture content in the wood corresponding to a temperature of 20°C and applications where the relative humidity of the surrounding air exceeds 85% only for a few weeks per year. The average wood moisture content is maximum 20%.
The production tolerances for BauBuche products are specified in chapter 2 of the BauBuche brochures.
The adhesives used in BauBuche products contain small quantities of free formaldehyde. The formaldehyde emissions from BauBuche products are within the range of untreated timber and thus far below the regulatory or recommended limit values.
Durability and care
The effect of UV light on beech lumber is similar to that on spruce. When installed indoors, the wood takes on a slight yellow tint. Outdoor elements tend to grey. The use of BauBuche for structures exposed to the elements is only permitted when protected by a roof (service classes 1 & 2). BauBuche is not approved for structures exposed to the elements without roof protection (service class 3).
The hydrophobic coating from Koch & Schulte GmbH Co. KG is available with special UV protection additives. For more information, see chapter 9 in the BauBuche brochures.
There is currently no company that offers impregnation of BauBuche. In addition, we have no information on experiences with impregnated BauBuche.
BauBuche is a kiln-dried wood product according to DIN 68800-1. In Germany, Austria and Switzerland, attack by insects is extremely unlikely. Damage by wood-destroying fungi (rot) can be effectively prevented by following the instructions in DIN-68800-2 "Wood preservation - Part 2: Preventive constructional measures in buildings". These measures are constructive in nature and aim at a classification of the timber in DIN use classes GK0 and GK1. For the use of BauBuche in GK0 and GK1, there is thus no need for chemical wood preservation against rot. Using BauBuche in GK2 is not recommended, and the material is not approved for use classes GK3 to GK5.
For constructions in regions where there is a risk of termite attack (Australia, certain areas in France), BauBuche must be treated with a special coating, like all other wood products.
We recommend treating the BauBuche elements with a moisture protection product, such as BauBuche varnish from Koch & Schulte GmbH & Co. KG, 57645 Nister, Germany. This coating provides temporary protection against damage from moisture for up to 12 weeks. The product is also available with permanent UV protection additives and can be ordered as a transparent varnish (natural colour) or with colour pigments. For advice on suitable protection, contact Adam Maciejewski, phone +49 171 23 72 832, e-mail a.maciejewski@kochundschulte.de at Koch & Schulte GmbH & Co. KG.
This issue would need to be discussed with the producer of the fire protection product in question. Normally, fire protection coatings must be applied directly to the timber. Also, they must not be covered by another varnish or paint.
Machining and application
No. Board BauBuche Q is no longer available. Board BauBuche S is recommended exclusively for bar-shaped elements. BauBuche Panel is a decorative timber construction product not covered by building regulations. It is therefore not suitable for structural elements.
In principle, deflection due to dead weight occurs in every material. Deflection depends on the actual span, the chosen beam dimensions and the load to be carried and must be calculated separately for every use case. Deflection can be reduced by cambering. Beam cambers of up to 1/100 of the beam length are permissible. Cambering of BauBuche beams should be discussed in advance with the manufacturer (see also section on standard and customised products).
BauBuche waste is classified as class A2 wood waste. Thermal recycling of BauBuche is possible at temperatures above 850 °C.
BauBuche can be treated with any commercially available coating system suitable for solid beech timber.
For the machining of BauBuche, take the same occupational health and safety precautions as for solid beech timber.
As a rule, all fasteners commonly used in timber construction are suitable for BauBuche. However, due to the high characteristic density of the material, a number of specific instructions apply. For more information on structural calculations of fasteners, please refer to our manual for structural calculation and chapter 5 of the BauBuche brochures.
Yes, planing and sanding are permissible as long as the cross-section remains square and a beam height of 80 to 2500 mm is maintained.
Short bore holes can be produced with 013C drill bits from FISCH-TOOLS, wood twist drill bits from Famag-Werkzeugfabrik GmbH & Co. KG or multi-purpose drill bits from Kanne Werkzeugtechnik GmbH. We advise against the use of auger bits.
For deep bore holes, we recommend using a drilling system that applies compressed air for cooling and the removal of chips and dust. One such system is the deep hole drilling machine from ZÜBLIN Timber Aichach GmbH (with drill bits measuring 4 to 12 mm in diameter and up to 3000 mm in length). For more information, see chapter 5 of the BauBuche brochure and www.zimmereibedarf.com.
Breakthroughs in Beam BauBuche GL75 are not governed by construction regulations and therefore not permitted by the ETA. For breakthroughs that cannot be avoided, we recommend a conservative design calculation and consulting the inspection engineer in charge of the project in advance. Openings with a clearance of more than 50mm are considered breakthroughs.
Production process
Laminated veneer lumber is produced with a phenolic resin adhesive. This type of adhesive offers great performance at reasonable cost and provides strong bonding. It is water-resistant and low in formaldehyde. The BauBuche strips in beams are glued with a phenolic resorcinol adhesive.
The adhesive content is 6%, determined upon application, i.e. when the adhesive is still wet. When fully cured, the adhesive content is approx. 4%.
Standard and customised products
Beam cambers of up to maximum 1/100 of the beam length are permissible. For cambering options, contact the manufacturer. The surcharge for the cambering of Beam BauBuche GL75 is EUR 75 per m3. In addition, two templates costing between EUR 1500 and 3500 need to be manufactured for every cambered beam size and type.
If only few beams need to be cambered, the costs for the templates are relatively high, so that it might be more economical to choose non-cambered beams with larger cross-sections.
Where many identical beams need to be cambered, the extra costs are low when compared with the price of beams with larger cross-sections.
This question cannot be answered in a general way. Let us look at an example: For spans of 11 m, cambering the girders by 20 mm results in an additional vertical clearance of 120 mm, as the height of the cross-section can be reduced from 960 mm to 840 mm (at a width of 280 mm). The extra costs for cambering are approx. EUR 3000 for two identical girders. For six identical girders, they amount to EUR 2000, and for 12 identical girders, they are around EUR 900. With 16 or more identical girders, cambering is actually cheaper, as the reduced costs arising from smaller cross-sections outweigh the expenses for cambering.
Pollmeier manufactures Beam BauBuche GL75 in the following dimensions: max. length = 18 m; max. width = 300 mm; max. cross-section height = 1360 mm. By combining multiple beams into block-glued beams, cross-sections of max. 600 mm x 600 mm can be achieved. Such elements are for instance used for posts in high buildings. A partner of Pollmeier has obtained approval for the production of Beam BauBuche GL75 with cross-section heights of up to 2500 mm and cross-section widths of maximum 1200 mm. The partner has of course the equipment necessary to produce such beams. However, the length of the beams is still limited to maximum 18 m. For customised cross-sections, please contact Pollmeier. The standard dimensions of BauBuche products are specified in the product overview in chapter 2 of the BauBuche brochures.
Yes. From a minimum order volume of 3 m3, Beam BauBuche GL75 is available in intermediate widths. For order volumes of less than 20 m³, there is however a surcharge.
As lattice girders are produced with joints, there are no specific upper limits regarding their dimensions. The maximum permissible size depends on the static strength conditions and the actual loads. Thanks to the high strength properties of BauBuche, the material caters for much larger spans than would be possible with lattice structures made from conventional glulam. For more information, see chapter 8 in the BauBuche brochures. On our reference pages, you find many reference projects built with BauBuche lattice girders.
The maximum width of BauBuche Panel is 1050 mm, corresponding to the cutting width of the horizontal block band saw. BauBuche panels can be machined like solid timber and thus glued together to achieve greater panel widths.
Building physics and planning
BauBuche has a thermal conductivity of 0.17 W/(m*K).
The specific heat storage capacity of BauBuche is around 1600 J/(kg*K).
The mean value is the arithmetic mean of all measured values. The characteristic value is determined according to EN 14374 and represents the 5% quantile of all measured values. This means that 95% of the measured values are greater than the characteristic value used in structural strength calculations. This guarantees a high safety margin.
The diffusion resistance of BauBuche has not yet been determined. It is however similar to that of heavy plywood, i.e. around µ = 150 to 250. This means that BauBuche can be used as a vapour retarder. BauBuche is however not suitable for the construction of vapour barriers.
The screw withdrawal force depends on the screw size, the screw angle and the characteristic density of the wood material. The high characteristic density of BauBuche results in a screw withdrawal force greater than that of softwood products. The method of calculation is specified in the technical approval Z-9.1-838.
According to ETA-14/0354, Beam BauBuche GL75 is approved for load-bearing and non-load bearing elements in buildings and timber constructions. BauBuche beam are approved for service classes 1 and 2 according to EN 1995-1-1. Given the low moisture content on delivery of 6% +-2% of Beam BauBuche GL75, and the high shrink and swell properties when compared with softwood (see chapter 3 of the BauBuche brochures), the material is suitable for use in service class 2. However, the material has been optimised for service class 1. As the equilibrium moisture content of wood in service class 2 is between 10% and 20% (normally 13% to 17%), changes in size – in particular those affecting the height of the beam – must be taken into account.
Observe the following:
- Direct exposure to water (e.g. in the form of condensate or water from sprinklers, for instance in riding halls) must be prevented.
- For use in service class 2, BauBuche, should be hydrophobized with BauBuche Primers + Varnish from Koch & Schulte GmbH & Co. KG. (see chapter 9 of the BauBuche brochures).
- Constructive wood protection according to DIN 68800 is always necessary.
Such a case might occur where rafters penetrate the thermal envelope of a building, forming a roof overhang. While such constructions are possible, all points addressed in the previous sections must be considered.
The cross-sections of BauBuche S are affected by shrinking and swelling to roughly the same extent as in solid beech timber. For details regarding the shrinking and swelling behaviour of BauBuche, see chapter 3 of the BauBuche brochures.
There are many different screws that have been specifically designed for use in hardwood and that are approved for BauBuche. For more information, see chapter 5 in the BauBuche brochures. All screws listed there have been tested by us and found suitable for use in BauBuche.
The following burning rates have been determined for BauBuche:
β0 = 0.65 mm/min for flat elements
βn = 0.70 mm/min for bar-shaped elements
BauBuche is classified in Euroclass D-s2, d0.
By applying a suitable fire protection coating, Euroclass B-s1,d0 according to EN 13501-1 can be achieved. Currently, coating systems from Teknos Deutschland GmbH (TEKNOSAFE 2467-00, transparent and TEKNOSAFE 2457-00, white, covering) are approved for BauBuche. These products must be applied according to the instructions in the relevant technical data sheets.
The applicable standards for load bearing timber constructions prescribe, that holes for pin-shaped fasteners in high-density timber (ρk > 500kg / m³) must be pre-drilled. There are no approvals yet that allow for the use of clamps in BauBuche without pre-drilling. For the fixture of panelling that does not need to meet any structural strength requirements, clamps with a diameter of 1.53 mm and 1.8 mm and an anchoring depth of up to 40 mm, or clamps with a diameter of 2.0 mm and an anchoring depth of up to 50 mm should be used.
Sustainability and certification
To qualify for DGNB Platinum certification, no chemical wood protection must be used. BauBuche is a kiln-dried wood product according to DIN 68800-1 so that there is normally no need for chemical wood protection. The declaration that the building is free of chemical wood protection must be submitted by the timber construction contractor.
The DGNB Platinum standard prescribes a maximum permissible formaldehyde content limit of < 0.10 ppm, corresponding to emission class E1. BauBuche Beam meets this criteria, as documented in ETA-14/0354. The actual formaldehyde emissions of BauBuche are very similar to those of natural wood and well below the above limit value.
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