* Based on values given in Table 3.1 of EC5.

* Based on values given in Table 3.1 of EC5.

This corresponds to climatic conditions leading to higher moisture contents than service class 2.

The highest values of timber strength will be obtained when structures function in service class 1 conditions and the lowest when they function in service class 3 conditions. The level of service class to be used in the United Kingdom for the type of element to be constructed is given in NA.2.2 in the UKNA to EC5.

Values for kmod based on the load duration referred to in and the above service classes are given in EC5, Table 3.1, and those for use with timber and some wood-related products are summarised in Table 2.4.

With timber, glued-laminated timber and laminated veneer lumber (LVL), certain characteristic strengths are affected by member size and where the appropriate size is less than the reference size given in EC5, the relevant characteristic strength can be increased by multiplying by a factor kh or kt. These factors are referred to in Table 2.5 and discussed in 2.3.6.

In EC5 the partial factor for material ym is enhanced to yM, taking into account uncertainty in the resistance model used for design together with the adverse effects of geometric deviations in addition to the effect of unfavourable deviation of material or product property. The value of yM for the ULS combinations of actions for persistent or transient design situations (referred to in EC0, as thefundamental combinations) as well as any accidental combination is given in Table NA.3 in the UKNA to EC5. A summary of the values to be used to derive the design value at the ULS, including for accidental combinations, is given in Table 2.6.

Table 2.5 Factors used in EC5 to take account of the effect of member size on strength properties

Size factor symbol

Function of factor

Characteristic property affected

Relevant item in EC5


Adjusts the characteristic bending


Solid timber, 3.2(3);

0 0

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