Module: Timber connections Unit: Dowel-type fasteners

Date Published

20 August 2022

Document Type

Category

Author

TRADA
Summary

There are four criteria designers should take into account when selecting and detailing connections for a particular application: load transfer (stiffness, ductility, robustness and differential movement), appearance, fire resistance and durability.

The traditional mechanical fasteners for structural timber connections are divided into two groups depending on how they transfer the forces between the connected members – ‘dowel-types’ and ‘metal connectors’.

Metal fasteners have negligible fire resistance and absorb and transfer heat quickly. Where required, fire protection with plasterboard is the most common solution.

Metal fasteners are efficient but the relative weakness of the timber perpendicular to the grain remains the governing factor.

Key Information

The most popular dowel-type fasteners are staples, nails, screws, bolts and dowels.

The most common nail is the round wire nail which is produced from a steel wire with a minimum tensile strength of 600 N/mm2 although twisted and annular shank nails have better pullout resistance than round nails.

Wood screws can be used for plain timber-to-timber joints.

Metal screws are often used for steel-to-timber and panel-to-timber joints.

The most common types of screws are countersunk head screw, round head screw and coach screw.

Case studies

The building follows the form of a pair of railway carriages; their long single-storey shapes with gently arched roofs are linked by a lower roof and one of the pair is set further back from the other, as if they were passing on different tracks.

In 2019 an explosion of colour appeared on the sedate lawn of Dulwich Picture Gallery. It was the Colour Palace, a timber pavilion painted in exuberant geometric patterns and stripes in a kaleidoscope of zinging neon colours.