Groundworks near me: foundations and ground preparation
The digging, footings, drainage and sub-base under extensions, outbuildings, walls and patios.
Groundworks as part of the build
Groundworks is the work that happens at and below ground level before anything goes up: setting out, excavation, foundations, drainage, oversite and sub-base. For us it is the first stage of the projects we build. Every extension, garden room, garden wall, retaining wall, patio and driveway we take on starts with groundworks, and it is the stage people never see once the job is finished.
Because we carry out the groundworks ourselves rather than handing them to a separate firm, the people digging the footings are the same people who will build the walls on them. That keeps levels, positions and drainage consistent from the trench to the roof.
House foundations for extensions
Extension foundations are designed to suit the ground and the load. Strip and trench-fill foundations are the most common for single and double-storey extensions. Where there are trees nearby, soft ground or deep made-up ground, deeper or engineered foundations may be needed. Building Control inspects the trench before concrete is poured, and the depth and width follow the approved design.
Ground conditions vary a lot across the area we cover. Dunstable and Totternhoe sit on chalk, while parts of the Lea and Ver valleys around Harpenden, Wheathampstead and Redbourn need floor levels and drainage checked more carefully.
Drainage and services
New foundations often meet existing drains. Manholes may need moving, pipes may need protecting where they pass under a wall, and building over or near a public sewer needs the water company's agreement. New rainwater from an extension roof or patio needs somewhere to go, whether that is an existing drain or a soakaway where the ground allows it.
Before we dig
Groundworks go best when the surprises are found early. At the site visit we look at access for a digger and skip, where spoil can be stored, the position of manholes and drain runs, trees close to the footprint, and any change in level across the plot. Where the ground is uncertain, a trial hole before the final design saves redesigning foundations once the trench is open. Neighbours are told when machines will be working, and the site is kept clean and tidy throughout, something we were taught on family extension jobs from the very beginning.
Ground preparation for patios, driveways and walls
Hard landscaping needs groundworks too. Patios and driveways need digging out, a compacted sub-base and falls that shed water away from the house. Garden walls need a concrete footing under the first course, and retaining walls need a footing sized for the soil they hold back, plus drainage behind them.
Questions people ask
- What does groundworks include?
- Setting out, excavation, foundations, drainage, ground preparation and sub-base for floors and hard surfaces. It is everything at or below ground level before the walls go up.
- Do you repair existing foundations?
- Our groundworks are part of new building work: extensions, outbuildings, walls and patios. If you are worried about movement in an existing house, a structural engineer or surveyor is the right first call.
- How deep do extension foundations need to be?
- It depends on the soil, nearby trees and the load. The design sets the depth, and Building Control checks the trench before the concrete goes in.
- What affects the cost of groundworks?
- Access for a digger, how much spoil has to be removed, the foundation depth the ground needs, drains to divert and any trees nearby. We give a free estimate after a site visit.
Related: extensions · garden rooms · retaining walls · patios · extension planning.