Structural design

Any work that touches a building's structure, meaning columns, beams, slabs or load-bearing wallsLoad-bearing wallA wall that carries part of the building's weight, such as floors, beams or the storeys above. It must not be removed or opened up without an engineer's design and the required permit., needs a structural design from an engineer. It works out how the loads will be shared after the change and specifies what replaces what is removed: a lintelLintelThe beam over a door, window or opening in a wall, which carries the bricks above it and passes their weight to the sides., a new beam, strengthening.

The structural design is usually tied to the permit the work requires. Without it, work on structural elements should not be done, however small it seems.

For a homeowner, the practical side is simple: if it isn't certain that a wall is an infill wallInfill wallA brick wall that fills the gap between columns, beams and slabs. It divides rooms, but it isn't built to hold the building up., or if the work comes near a column or beam, the first step is an engineer, before any hammer.