Our Magazine

Sherpa News

New ETA-12/0067 for XS to XXL

As of February, planners and contractors in timber construction have beenbenefiting from the innovations of ETA-12/0067. In particular, the fire protection solutions for verifications up to R120 enable the use of SHERPA system connectors in demanding constructions.

The core of the expansion is the newly created Appendix 6 from page 141, which is dedicated exclusively to the fire resistance of the M, L, XL and XXL series. The framework conditions that must be given for each connector in order to withstand a fire load of 30, 60, 90 or 120 minutes are clearly presented on just three A4 sheets.

​Fire test at the IBS in Linz for 90 minutes of fire resistance
​Fire test at the IBS in Linz for 90 minutes of fire resistance

Cross section or load bearing capacity
The basis for the verification is a sufficiently dimensioned timber cross-section. The calculation is made by adding the respective table value to the minimum cross-section of the cold design. For the first time, a distinction is made between the requirements for torsionally rigid and torsionally soft connections in case of fire. For both connection cases, two factors are available for the residual load capacity: The planner can freely decide whether to focus on a minimum timber cross-section or a maximum residual load-bearing catempacity. The drawings on page 143 allow a clear assignment of the individual table values. It should be noted that for R90 and R120 a minimum length of 100 millimetres is required for the special screws.
SHERPA fire resistance R30-R120
Information on the additional wood cover depending on the SHERPA type and fire resistance

Fire protection coating “Fire Shield”
An innovative solution is now available for connection applications where the timber cross-section is not sufficient, or for constructions that have already been executed and for which a fire protection certificate is subsequently required: By locally applying the intumescent fire protection coating “Fire Shield”, the timber component can be reduced by 10 millimetres per side exposed to fire. The application is done with brushes, rollers or airless equipment, whereby the minimum application quantity of 1,245 grams per square metre must be observed.

Application of the fire protection coating“Fire Shield” on the secondary beam.

Safe connection joint width
In the case of timber construction connections, the joint design also plays a decisive role in the event of fire. In visible-quality constructions, fasteners are usually milled in, thus they are optimally protected from the effects of temperature in case of fire. Depending on the size of the components, a shadow gap may be required to ensure smooth assembly. In order to be on the safe side even in these cases, joint widths of up to 5 millimetres can be made.

Connection joints up to 5 mm without additional fire protection measures

“Fire Stop” for joints
For economically optimised constructions, where the connectors are merely screwed on and are therefore visible, the proven fire protection laminate “Fire Stop” is used. Whether it’s R30, R60, R90 or R120: Up to four strips with a width of 20 millimetres are glued and/or stapled side by side along the connector contour. It is fixed to the side timber of the main beam or to the end timber of the secondary beam. In case of a larger quantity requirement, there is also the possibility of producing the necessary width with a single strip (with a width of 40, 60 or 80 millimetres).

Three strips, each 20 millimetres wide, for fire resistance R90

Connect hardwood with ease
Raw density correction factors are available for calculating the load-bearing capacity values for different hardwood materials. Distinctions are made between ring-porous (ash, oak and chestnut) and scattered-porous hard-woods (beech, birch and poplar). In all hardwood applications, pre-drilling of the special screws is only mandatory for the torque screws in the end grain that are aligned parallel to the wood grain.

Testing with BauBuche at holz.bau forschungs gmbh