Many structural problems originate from the insufficient performance of connections. The most common connection type used in timber structures is the dowel-type connection. Dowel-type connections are easy to manufacture and can be designed for a large load range.

In the formula for determining strength according to EC5 [1], embedment strength of wood is the basic parameter. Embedment strength values are dependent on wood density and dowel diameter. The formula for embedment strength is derived from experiments.

The purpose of this study is to specify the influence of various parameters on the embedment strength and stiffness of wood specimens under a steel dowel. Strength design in EC5 does not consider for e.g. increased roughness between dowel and wood, neither is the positive influence of reinforcement by e.g. screws covered

Embedment tests are performed according to the European [2] and American standard [3] for embedment tests and the differences will be reported.

Embedment tests in fiber direction are performed on wood specimens with different densities, in which moreover the holes were drilled with various drilling devices. Dowels with different roughness (roughened with rasps or engrailment) were inserted, some of the specimens were reinforced by screws to prevent cracking of the wood.

These embedment tests are the continuation of tests on the contact stiffness of wood on steel and the dependence on wood roughness and density.