binderholz Mass Timber Manual

BINDERHOLZ CLT BBS | TOP LAYER SORTING Surface quality BBS* Features Visible residential AB Visible commercial BC Non-visible C Knots Healthy, firmly grown-together knots: Permitted Black knots: Permitted in singular cases permitted permitted Compression wood permitted permitted permitted Dowels & corrected resin pockets permitted permitted permitted Appearance balanced no requirements no requirements Resin pockets Sporadically up to 1/8‘‘ x 2‘‘ (3mm x 50mm) permitted permitted permitted Insect infestation not permitted not permitted sporadically permitted Heart center streak sporadically permitted permitted permitted Quality of the surface finish Small sporadic flaws permitted, e.g., small tears caused by wood plane Small sporadic flaws permitted, e.g., small tears caused by wood plane Flaws permitted Bark pockets sporadically permitted sporadically permitted permitted Checks sporadic checks on surface permitted sporadically permitted permitted Discolouration Light discolouration permitted permitted permitted Edge bondline Singular open joints up to max. 1/16‘‘ (1mm) are permitted Occasional open joints up to max. 1/8‘‘ (2mm) are permitted Open joints up to max. 1/4‘‘ (4mm) are permitted Wane not permitted not permitted permitted The change in moisture content and the effect it has on the visual appearance takes place over three stages: Production: Cross-laminating the kiln-dried lamellas (wood moisture content 10 % +/- 2 %) reduces the natural shrinking and swelling of CLT BBS to a minimum. Shell construction and assembly : CLT BBS is subject to the natural seasonal climate changes during the shell construction and assembly period. Changes in the moisture content on account of prevailing climatic conditions are therefore possible. Building use: After a period of up to three heating seasons the mean moisture content of CLT BBS stabilises at around 8-10%. These changes in moisture content can lead to optical changes such as checks and gaps in CLT BBS with visible quality surfaces. These have no influence on the static properties of CLT BBS. Even the greatest care during production and minimum changes in moisture content cannot completely rule out the appearance of checks and gaps. Coatings applied to visible quality surfaces can enhance their appearance. Thicker outer layers in CLT BBS have a positive effect on the load-bearing capacity; however, it is also subject to greater swelling and shrinkage and therefore to greater check and/or gap formation. * Based on DIN EN 13017-1:2000-01 and in compliance with the strength grading EN 14081-1 For our CLT BBS in visible quality AB and BC , we have used the tried and tested double-length layer for many years. It always consists of a 0.79‘‘ (20mm) thick visible top layer glued to a second longitudinal layer with a thickness of at least 0.79‘‘ (20mm). In this way we can combine the best visible quality and a high dimensional stability of the top layer with a strong load-bearing capacity of the element. The true quality of cross-laminated timber in visible quality does not become apparent until 1 to 3 heating seasons have passed. Use our experience to your advantage.