Foundations in the examination

Where the instructions require them

Twice, explicitly.

In the calculations: the form, size and approximate carbon of all principal structural elements including the foundations. The list of likely principal elements names piles and pile caps, reinforced rafts and pads, and balancing beams within the foundation system, as well as retaining walls.

In the drawings: appropriate plans and sections including foundations.

So a paper with a beautifully designed superstructure and no foundation is incomplete in two sections at once, and foundation type is one of the six categories that make two schemes distinct in section 1a. It runs through the whole paper.

Reading the ground conditions in the brief

The question gives you ground information for a reason, and it is usually the constraint that decides between your two schemes. Read it for:

• Bearing capacity and depth of competent stratum, which sets pads against piles.
• Made ground, fill or contamination, which can rule out shallow foundations, or make disposal a programme and carbon issue.
• Groundwater, which affects excavation, buoyancy and construction sequence.
• Slopes, adjacent structures or existing foundations, which affect both design and the method statement.
• An existing structure to reuse: increasingly common, and an explicit invitation to take up the reuse opportunity the instructions mention.

Keeping foundations from being the casualty of the clock

They are last in the natural order of work, which is why they get squeezed. Two habits fix it:

• Size them early, at scheme stage. You need the foundation type in section 1a anyway. Carry an approximate size forward rather than starting from nothing in the afternoon.
• Draw the foundation plan when you draw the general arrangement, not after the details. It is quick if the column loads are already estimated, and it is required.

What to check

For most foundation elements, the same principle as elsewhere applies: the worst case, checked properly, rather than every case checked lightly. Bearing pressure or pile capacity, then the structural design of the element: bending and shear in a pad or cap, and the punching check where the column lands. For a retaining wall, overturning, sliding and bearing before the stem and base design.

Say what you have assumed about the ground and where the assumption came from. The instructions ask for assumptions to be stated, and ground is where assumptions matter most.