Site setup and foundations: what happens and what to check

The foundation stage is the first one you cannot fix later. Once the concrete is poured, nobody can check what is under it. Your job at this stage is to make sure the right people look at the trench before the pour, that you have a record of it, and that the paperwork, safety appointments and insurance are in place before the first machine arrives.

What happens, in order

1. Safety appointments and notice. Before work starts, your commencement notice must be valid and you must have appointed the project supervisors described below. See commencement notices and BCAR.
2. Site set-up. The builder fences the site, puts up signs, arranges a temporary water and power supply, a skip and a place for deliveries. Access is often the first problem: a narrow lane or a soft verge may need a temporary stone road so that lorries can reach the site.
3. Topsoil strip. The topsoil is scraped off and stored. Keep it on site if you need it for landscaping; removing and then buying it back costs money.
4. Setting out. A surveyor or the builder marks the corners of the house from the drawings and the planning permission. Check the position against the permitted site layout, the required distances to boundaries and the required finished floor level before anything is dug. A house built in the wrong place is a planning problem, not a building one.
5. Excavation. The digger opens the trenches or the whole footprint down to the level on the drawings.
6. Inspection. The engineer or certifier looks at the bottom of the excavation, the ground it sits on and the reinforcement.
7. The pour. Concrete is placed, levelled and left to cure. The builder normally orders ready-mixed concrete and the delivery has to be timed so that the pour can finish in a day.
8. Setting-out check and start of the walls. After curing, the first blockwork or the base for a timber frame goes on.

Foundations: the common types

Your engineer chooses the type from the ground and the weight of the house. Ask for the reason in plain words.

Type	What it is	Typical use
Strip	A continuous trench of concrete under the load-bearing walls	Firm ground at a modest depth
Raft	A single reinforced slab under the whole house	Softer or variable ground, or where trenches would collapse
Piles or ground beams	Concrete columns or beams taking the load to deeper, firmer ground	Poor ground, high water table or sloping sites

Rock, a high water table, peat or fill can all change the answer. A site investigation or a trial pit before you design (see site suitability assessment) is much cheaper than finding out when the digger is already there.

Who does what

• Builder or your own trades: excavation, reinforcement, concrete and the setting out.
• Engineer or designer: specifies the foundation and confirms the ground. For a house with an assigned certifier under the Building Control Regulations, the certifier’s inspection plan should list foundations as an inspection point.
• Assigned certifier: inspects at the stages in the inspection plan and keeps the records that support the certificate on completion. See assigned certifier explained.
• Lender’s inspector: confirms to the bank that the foundations are in. This is separate from the certifier’s work. Your lender may want a certificate confirming the foundations are complete before it releases the first stage payment.

Safety: you are the client

When you have a house built, you are the “client” under the construction safety regulations. You must appoint, in writing, a project supervisor for the design process and a project supervisor for the construction stage, and each must accept in writing. The Health and Safety Authority publishes a homeowner guide with a template form and questions to ask about competence. If you are managing the build yourself, you may be taking on more of this role. Check how it applies to you before you start, and see insurance when you project manage.

What to check and photograph before the pour

Take photographs of each of these, with a tape or a marked rod in the picture and a note of the date.

• The trench or excavation bottom. Firm, undisturbed ground, no standing water, no loose spoil or soft pockets. Water at the bottom is not automatically a problem, but the engineer should decide.
• Depth and width against the drawing, measured at several points.
• Reinforcement where the design has any: bars the right size and spacing, held off the ground on spacers so the concrete can surround them.
• Services and sleeves. Water, drainage and electrical ducts that must pass through the foundation are much easier to include now than to cut later.
• Radon and damp measures. Radon is a radioactive gas that comes from the ground and is a known cause of lung cancer. Ask your designer how the house deals with it. Whether this is a sump, a barrier or both will show up at the next stage, but any pipes or ducts through the foundations need to be in place now. See substructure and floor slab.
• Concrete delivery docket. Keep the delivery notes, which state the concrete strength class. The strength must match the specification.

If the engineer cannot attend, ask for a written instruction from them that the work may proceed, based on your photographs and the builder’s description. That is a decision for the engineer, not for you.

What goes wrong, and what it costs

• Soft or variable ground. The most common surprise. The fix is deeper excavation, wider or reinforced foundations, or a different type. Ask your engineer for the extra volume of concrete and who bears the cost under your contract.
• Pouring before inspection. If concrete goes in before anyone has looked, the only ways to check it are coring and testing, which are slow and expensive and may not satisfy the lender or certifier. The remedy can be a structural opinion at your cost.
• Wet weather. A flooded trench has to be pumped out and sometimes dug deeper. A pour in heavy rain or frost can damage the concrete. The builder should have a plan to protect it.
• Wrong set-out. Check the position yourself against the planning drawing. A mistake of 300 mm can break a boundary condition or the permitted level.
• Poor access. Lorries stuck or damaging a neighbour’s lane lead to delays and claims.
• Undeclared services. An old drain, a water main or an overhead line on or near the site. Know where they are before digging.

Payments at this stage

Many lenders release the first stage payment once the foundations are complete and certified, and some release money earlier for the site purchase. That leaves you to pay for the site works, fees, utility applications and the foundations from your own money until that first release. Use the stage payment planner to see the gap, and read staged drawdown explained for how inspections and releases fit together.

Check the details in your own contract and offer. In particular, agree with your builder whether the foundations are paid when they are poured, when they are inspected, or when the lender releases the money.

Site and insurance risks

• Open excavations. A deep trench is a hazard for visitors, neighbours’ children and animals. Fence it and keep it covered or lit as appropriate. You, as the client, still have responsibilities if someone is hurt.
• Plant and fuel theft. Diggers, tools and fuel are targets on a quiet rural site.
• Damage to neighbours. Vibration, undermining a boundary wall or a burst service pipe can all lead to a claim against the person who commissioned the work.
• Cover should start on day one. Contract works and public liability cover should be in force before the first machine moves, not on the day the first payment arrives. Check who is insured for what under your contract; see insurance when you project manage and what lenders require. When you are ready, the cover checker lists the types of cover that match how you are building.

Before you move to the next stage

• The engineer or certifier has recorded their inspection, with a date.
• You have the photographs, the concrete delivery notes and any written instructions.
• The stage report your lender needs is ready or booked.
• You know what the next trade needs: the substructure and floor slab follows.

The full sequence is in the stages guide.