Design MTT CLT to Eurocode 5

Binderholz (Binderholz Bausysteme GmbH, Fugen, Austria) manufactures BBS cross-laminated timber. It is recognized under ETA-06/0009, issued by DIBt. SPEC Toolbox designs the panels to Eurocode 5, using the characteristic values of the assessment.

MTT manufactures cross-laminated timber in Germiston, Johannesburg, from South African plantation pine graded S5 and S7, with a eucalyptus option. Pine lamellae are 22, 33 or 44 mm thick and 106 or 145 mm wide; eucalyptus lamellae are 16 or 22 mm thick and 175 mm wide. Lamellae are not edge glued.

Sixteen standard layups cover 66 to 231 mm in 11 mm steps: 3 ply from 66 to 132 mm, 5 ply from 143 to 220 mm, and 231 mm as 7 ply. Panels are produced up to 1800 mm wide and 6000 mm long, bonded with a fire rated polyurethane adhesive (Henkel HB S159) and supplied at 10.5 percent moisture content, ±2 percent.

Tolerances are ±6.4 mm on length, ±3.2 mm on width and ±2 percent or 1.6 mm on thickness. Surfaces come as Domestic Visual (A1, 80 grit), Industrial Visual (A2, 60 grit) or Non-visual. Borate treatment, thermal modification and tinting are available. MTT is FSC certified.

Load-bearing walls, floors and roofs. The declared data covers dry, internal service conditions at an ambient moisture content below 15 percent. Components are robotically cut and machined to specification, and any surface quality can be selected per element.

• Panel level stiffness and resistance are declared for every layup in both directions: effective bending stiffness from 180 to 5700 ×10⁹ Nmm²/m of width, moment resistance from 8.0 to 72.8 kNm/m and shear from 15.8 to 55.4 kN/m.
• A plantation eucalyptus option sits alongside the pine grades, declared at 25.9 N/mm² characteristic bending strength, 12.0 kN/mm² mean modulus and 700 kg/m³ mean density, against 11.5 N/mm², 7.8 kN/mm² and 420 kg/m³ for S5 pine.
• Thickness granularity of 11 mm across sixteen layups, a consequence of the 22, 33 and 44 mm lamellae, lets a panel be tuned close to the required capacity.
• Charring rates are species specific, derived from fire tests on SA pine and eucalyptus CLT walls carried out at Stellenbosch University.
• Thickness is held to ±1.6 mm, and each element is marked with an identifier after layup, grade, species and moisture checks.

MTT CLT panels appear across the SPEC Toolbox CLT modules, worked to Eurocode 5: CLT floor, CLT wall, CLT shear wall, CLT diaphragm and CLT floor penetration. They also carry into the screw connection module and the panel-to-panel connection details (spline, butt joint and half-lap), together with the CLT floor-to-glulam beam, CLT floor-to-floor and CLT wall-to-wall connections.

Panel behaviour is taken from the integrated database using the MTT declared values, and the same values are used for design to the Australian and New Zealand standards. Fire design, vibration and other verifications not covered by the current Eurocode 5 can be checked against the new Eurocode 5 and other relevant documentation.

Design follows Eurocode 5 (EN 1995-1-1). The panels are not covered by a European Technical Assessment and are not CE marked. MTT cross-laminated timber is certified to SANS 8892 for performance rated CLT, with lumber to SANS 1738, finger jointing to SANS 10096, adhesives to SANS 10183-2, and SATAS plant auditing. The characteristic values for S5 pine, S7 pine and eucalyptus, and the effective stiffness and resistance of each layup, are declared in the MTT design guide and are the values used in design. The span and fire tables in that guide are concept design guidance derived to SANS 10160-1, so they sit outside the Eurocode 5 verification.