What is diagonal placement?
Diagonal placement means set at an angle to the main direction — in practice usually 45 degrees. It describes a direction, not a material or a component: a brick, a tile, a baluster or a buttress can all be set diagonally.
Where you meet it
- Brickwork. The best-known use is the dogtooth course: a course of bricks laid diagonally so that the corners project from the face like saw teeth. Often used as a finish below the eaves or as a decorative band in a facade.
- Buttresses. On gothic churches the corner buttresses frequently stand diagonally, at 45 degrees to the corner of the building, so that one buttress takes the thrust from two wall planes.
- Tiling and flooring. Laying tiles diagonally makes a room look wider and disguises walls that are not square. It does produce more waste: for diagonal laying, allow 10 to 15 per cent extra tiles, against roughly 5 to 10 per cent for a straight lay.
- Timber. Components meeting at 45 degrees, such as a mitre in an architrave or a brace in a roof truss.
- Railings. Balusters welded or fixed diagonally between the top and bottom rails.
| Diagonal lay | Allow 10 to 15 per cent extra tiles |
|---|---|
| Straight lay | Allow roughly 5 to 10 per cent extra tiles |
Practical points
- Always set out a diagonal line first. For diagonal tiling, start from the centre of the room with a chalked cross at 45 degrees. Start at a wall and the error accumulates all the way across.
- Check the room for square with the 3-4-5 method before laying diagonally. Diagonal work only disguises out-of-square walls if you spread the discrepancy evenly across the perimeter cuts.
- In brickwork the brick size sets the look. A diagonal course projects roughly half a header width; the further the bricks project, the more vulnerable the course is to frost and water. The course must shed water rather than act as a channel.
- Mitres in timber forgive nothing. A 45-degree cut shows every error; cut test pieces and set the saw before cutting the real work.
Checks before laying tiles diagonally
- Start from the centre of the room: Mark a chalked cross at 45 degrees; starting at a wall lets the error accumulate.
- Check the room for square: Use the 3-4-5 method before laying diagonally.
- Spread the discrepancy: Divide it evenly across the perimeter cuts to disguise out-of-square walls.
Related terms
- Bricklaying
- Rising brickwork
- Facing brick
- Mitre joint
- Roof truss
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