External works and levels design
Design of external levels, paving, steps, ramps and falls around buildings.
About this service
The ground around a building has more to do than look good. It has to carry rainwater away from walls, give level or gently sloping access to doors, meet the street and neighbouring gardens at sensible heights, and keep soil off the brickwork. When a new building or extension changes these levels, someone needs to design them. Otherwise the problems tend to appear on site, where they are expensive to fix.
Our external works and levels design covers paving, steps, ramps, retaining edges and the falls that carry water to drains or soakaways. It is useful for new homes, larger extensions with level thresholds to the garden, sloping sites and any project where landscaping must tie into drainage. We coordinate with your architect, landscape designer and drainage engineer so that levels, drainage and structure work together.
On sloping London sites, levels design often reveals the need for retaining edges or walls where the ground changes height. Small edges and planter walls can usually be detailed within this service, while taller walls need full retaining wall design. Like all our design work, the drawings go through our three-step quality control process, with final sign-off by our Head of Engineering.
When you need it
- You're landscaping around a new building or extension
- Levels need to work for drainage and access
What's included
- Levels design
- Falls and drainage coordination
- Steps, ramps and retaining edges
- Drawings
How it works
- Review survey and designWe start from a topographical survey and the architect's plans, identifying floor levels, door thresholds, boundaries, existing drainage and fixed levels at the street and neighbouring gardens.
- Set the levelsWe design finished levels across paths, patios, driveways and lawns, with falls away from the building and towards drainage points, adjusting where access or boundaries constrain them.
- Detail steps, ramps and edgesWe design steps, ramps and retaining edges to suit the level changes, with suitable gradients, landings and handrail positions where needed, keeping step heights consistent so they are comfortable and safe to use.
- Coordinate drainageWe check that falls direct water to channels, gullies or permeable areas, and coordinate with the drainage design so that pipe depths and outfall levels work.
- Issue drawingsWe issue levels and external works drawings with spot heights, falls and key details for paving edges, channels and steps, ready for pricing and construction.
What you receive
Level thresholds, damp proof courses and surface water
Level access to the garden is popular, but it conflicts with a basic rule of construction. Ground and paving are normally kept well below the damp proof course to stop rain splashing up and water soaking into walls, and Building Control will expect this unless there is a properly designed alternative. A level threshold usually needs a drainage channel at the door, falls away from the building and careful waterproofing details.
Approved Document M gives guidance on accessible approaches to new homes, including maximum gradients and landing lengths for ramps, and it may apply to your scheme. Building Control will confirm the requirements. Surface water from new paving also needs somewhere to go, and many councils expect it to be managed on site rather than sent straight to the sewer. Our SuDS strategy can be coordinated with the levels design.
Projects that used this service
Frequently asked questions
What fall should paving have?
Paving needs enough fall to shed water, but not so much that it feels steep or creates a trip risk. The right gradient depends on the surface, with smooth finishes needing less fall than textured ones. We set the falls on our drawings for each area, always away from the building and towards a drainage point.
How far below the damp proof course should ground level be?
As a general rule, ground and paving next to a wall are kept around 150 millimetres below the damp proof course, to limit splashback and damp. Where level access is needed, a drainage channel and special detailing are used instead. Building Control will confirm what is acceptable for your project.
Do I need an engineer to design garden levels?
For a simple patio, probably not. For a new building or extension, a sloping site, a level threshold, steps or ramps on an access route, or anywhere the ground changes height against a boundary, an engineered levels design avoids drainage problems, damp and disputes with neighbours. It also gives your builder clear information to price from.
How much does external works and levels design cost?
Our external works and levels design starts from £750 + VAT. Larger sites, significant level changes and retaining edges increase the fee. We confirm a fixed fee in writing before any work begins, and our typical turnaround is 10 working days.