What is a diagonal brick course?
A diagonal brick course (Dutch: stroomlaag) is a single row of bricks laid at an angle and used as a packing course when repairing masonry foundations or when underpinning an existing building to form a cellar. In Dutch, filling the gap this way is called aanstromen. The course closes the last space between new work and the existing masonry above, much as pinning up does in British underpinning.
Its advantage is that the angle of the bricks can be chosen freely. The steeper the bricks, the taller the course, so it fills exactly the height that remains without cutting bricks. If the bricks stand fully upright, it becomes a soldier course. Similar angled courses can also be seen in old farmhouses in Belgium and France, where they appear as coarse, alternately leaning brickwork in the walls.
How it was done
The foundation was never replaced in one go. Work was done in alternate sections: first a short length was renewed and left to harden (using rapid-hardening cement), then a day later the sections in between. That way the wall above stayed largely supported throughout.
Application
- Recognise it in existing work. A row of angled bricks directly under old cellar or foundation masonry often points to an earlier repair.
- Do not tackle foundations yourself. Foundation repair and underpinning should always involve a structural engineer, who sets the sequence, the length of each section and the temporary support.
- Expect concrete today. The diagonal brick course is rarely used now; reinforced concrete cast in suitable formwork is the usual choice.
- Work in short sections. The principle still applies to modern methods: never remove a long stretch of foundation at once.
Common mistake: confusing it with a diagonal soldier course. Both use angled bricks, but a diagonal soldier course is a course in the walling above ground, while the diagonal brick course is a packing course within the foundation.
Related terms
- Soldier course
- Diagonal soldier course
- Foundation repair
- Reinforced concrete
- Formwork
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