How to prepare a foundation excavation
Preparing a foundation excavation starts before the machine arrives. You need the design, the setting-out and information about the site. Deciding the depth yourself, “the same as next door”, is no substitute for the design documents for your particular building.
Before you start
Agree the scope and conditions of the work with the person in charge of the build. The setting-out should be done by the appropriate person, and the operator should have clear information to work from. Point out underground services, existing structures and obstacles.
Prepare the access route and a place to stockpile the excavated soil. The soil should not end up blocking the next stage or making conditions worse next to the excavation. It is worth deciding in advance what will happen to it.
During the work
The dimensions and levels come from the design. Do not correct the bottom of the excavation by adding soil or digging deeper as you see fit, without agreement. If the soil changes, water appears or other unforeseen conditions arise, report the problem to the person responsible.
Do not go into an excavation whose safety has not been assessed. Preparing for concrete and carrying out the work safely require proper organisation on site.
After excavation
The condition of the bottom can change because of rain, drying out or machinery moving around. That is why the next stage should be planned and the excavation checked before concreting. There is no fixed number of days that every excavation can be left without an assessment.
If water appears, find out why and decide what to do. Removing it does not on its own confirm that softened ground is ready. Before you order concrete, make sure the element has been inspected and approved to the extent required.
Homeowner’s checklist
- the design documents and the setting-out are ready;
- underground services and obstacles have been reported;
- the access and a place for the excavated soil have been agreed;
- the levels and the condition of the bottom have been checked;
- a fresh assessment has been made after a change in the weather;
- the date for the concrete matches when the work will be ready.
If you are looking for a contractor, see foundation excavation in our offer. Our concrete for foundations, and preparing the ground before concreting, are part of the next stage.
Questions about the excavation
Who sets out the building?
Setting-out should be arranged in line with the requirements for the build. It is not automatically part of the operator’s job.
How long can an excavation be left open?
It depends on the soil and the weather. A check before concreting is needed however long it has been.
What about standing water?
Report it to the site manager; agree how it will be removed and how the bottom will be assessed before any further work.