What is a strijkbalk?
A strijkbalk (Dutch) is the first joist in a timber floor that runs parallel to a wall, lying alongside it rather than bearing on it. The name comes from the Dutch verb strijken, meaning to pass along something. There is no single fixed English term; it is simply the joist next to a wall that runs in the same direction as the joists. The German equivalent is Streichbalken.
The joist is set with a small gap from the wall. The Dutch building reference by Joost de Vree gives about 50 mm as typical and 50-120 mm as the usual range. A larger gap leaves the floorboards along the wall unsupported over too great a width, so they can sag under heavy loads.
The gap also protects the timber. Against an external wall, a joist in direct contact with the masonry picks up penetrating damp and rots too quickly. Fixing directly to the wall is only an option on an internal wall.
Recognising it
Lift a floorboard or look into an open ceiling. On two walls you see joist ends bearing on the masonry. On the other two walls the joists run parallel: the joist closest to each of those walls is the strijkbalk.
In practice
- Measure the gap. If it is well over 120 mm, give the boards along the wall extra support, for example with a batten or noggings fixed between joist and wall.
- Keep it dry. Do not pack the gap against an external wall with material that traps moisture.
- Check for rot during renovation. A joist alongside a damp external wall is a known weak spot. Probe the timber with an awl; soft wood points to decay.
- Keep the wall restraint. Walls parallel to the joists are often tied to the floor with metal straps running across several joists. Reinstate these when replacing the joist.
Common mistake: screwing a new joist tight against an external wall to stiffen the floor. Without a gap, damp from the wall moves into the timber.
Related terms
- Beam layer
- Common joist
- Trimmer joist
- Beam anchor
- Beam end
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