Groundworks are the part of a project nobody sees, and the part everything else depends on. It applies whether you’re building an extension, a new build or landscaping a garden: what happens at and below ground level sets the standard for whatever gets built on top of it, and problems here tend to surface years after everyone’s forgotten they were ever a risk.
This guide covers what groundworks actually involve and the parts of the job, from foundations to drainage, worth understanding before you start.
What are groundworks?
Groundworks cover everything needed to prepare a site and get it ready for construction, up to and including the ground floor: preparing the site, digging and laying foundations, installing drainage and services, forming the base the structure sits on. On a landscaping scheme, it also takes in the levels, drainage and hard surfaces that make a garden usable day to day.
What groundworks include
The exact scope depends on the project and the site, but groundworks usually cover:
- Site clearance and setting out. Clearing vegetation, removing obstructions, stripping topsoil, marking the building out precisely from the approved drawings. This is often where old drains, tree roots or buried rubble from a previous building turn up, none of which show on a drawing.
- Excavation and foundations. Digging to the right depth for the ground conditions and laying the foundations that carry the load of the whole building.
- Drainage. Below-ground pipework for foul water from the building and surface water from roofs and hard surfaces, including any soakaways or sustainable drainage.
- Services. Ducts and connections for water, electricity, gas and data, laid so they can be brought into the building cleanly later.
- The oversite and ground floor. Hardcore, a damp-proof membrane and insulation, then the concrete slab or a beam-and-block floor.
- External works. Retaining walls, driveways, patios and levels, tying the finished building into the ground around it.
Why groundworks matter so much
Foundations and drainage are the two things that are hardest, and most expensive, to fix once the building is up. A foundation sized for the wrong ground conditions, or drainage that can’t cope with what comes off the roof, tends to show up as movement, damp or flooding well after the scaffold’s come down and everyone’s moved on. That’s the whole argument for spending proper time on the survey and the setting out before anything else starts.
Foundations: one size does not fit all
The right foundation depends on the ground. Firm, even ground might suit a straightforward strip or trench-fill foundation. Poor or variable ground, or trees nearby, often calls for a raft that spreads the load, or piles reaching down to something solid. This decision comes from the ground investigation, not a guess, and a structural engineer sizes it where the ground calls for one.
Drainage, soakaways and surface water
Drainage does two separate jobs: taking foul water away to the sewer or a treatment system, and dealing with the surface water running off roofs, driveways and patios. Increasingly, that surface water has to stay on site rather than get piped straight to the sewer, usually managed through a soakaway or a sustainable drainage system. On a landscaping project this matters just as much. A garden that floods almost always comes down to drainage that was never properly solved in the first place.
How we can help
Groundworks and landscaping are what we do most often. Through our landscaping and groundworks service we handle the below-ground stage from survey through to foundations, drainage and external works, and tie it into the build or garden above it. Pricing depends on the ground conditions and scope, which usually only become clear once we’ve had a look at the site ourselves, so that’s when we quote properly rather than guessing beforehand. If there’s a tricky bit of ground, we’d rather flag it before we start than let it turn into a surprise halfway through.
Frequently asked questions
What do groundworks include?
Everything needed to prepare a site up to ground floor level: clearing and setting out, excavating and laying foundations, foul and surface water drainage, service ducts, and the base the structure sits on. Landscaping projects also bring in levels, drainage and hard surfaces like driveways and patios.
Why are groundworks so important?
Because the rest of the building sits on top of them, and mistakes here are the hardest to see coming. Get the foundation or the drainage wrong and it tends not to show for a while, by which point it’s a much bigger job to put right than it would have been at survey stage.
What type of foundation will my project need?
Depends entirely on the ground. Firm, even ground can often take a strip or trench-fill foundation; poor or variable ground, or nearby trees, tends to push things towards a raft or piles instead. A ground investigation settles it, not guesswork.
What is a soakaway?
A below-ground structure that collects surface water from roofs and hard surfaces and lets it drain away into the surrounding ground rather than into the sewer. It’s a common way of meeting sustainable drainage requirements, and getting the size and position right is what keeps a garden or driveway from flooding.
Do groundworks need Building Regulations approval?
Yes. Foundations, drainage and the ground floor all fall under Building Regulations, with inspections at set points, typically before foundations get poured and before drains are covered over.
Useful links
Official guidance on the rules covered in this guide:
