Datums
Finished floor, damp-proof course and external levels should be related to the existing property before excavation.
Groundworks
Groundworks for extensions
Extension groundworks connect the proposed building to real ground, existing drainage and the levels of the house and garden.
Photos, drawings or a short description can help explain the current condition.
Groundworks · Groundworks for extensions
Start below the finished surface
The groundwork stage turns drawings into fixed dimensions. Errors in position or height carry through every later trade, so setting out, inspection and communication with the superstructure team are critical.
Ground, access and water
Drain coordination
New and existing drainage needs resolving alongside foundations, sleeves and any build-over requirements.
Backfill and access
The method of filling around new work should protect walls and leave suitable preparation for future paving or landscaping.
What to mention
What Flyson needs to understand about the ground
- Describe what is already known about datums.
- Explain the priority or constraint around drain coordination.
- Include enough context to discuss backfill and access without assuming a product or method before the property is understood.
Questions specific to groundworks for extensions
Can groundworks start before final drawings?
Starting with incomplete dimensions or drainage information creates avoidable risk. The construction issue should be sufficiently resolved first.
Are spoil removal and stone included?
A good quotation should state assumed quantities, disposal, imported materials and what changes if ground conditions differ.
How are floor levels agreed?
They should be set from a clear datum linked to the existing house and intended external thresholds, not estimated independently in the excavation.
Continue exploring groundworks
Groundworks for driveways
The surface of a driveway lasts only as well as the formation, sub-base, edge restraint and drainage beneath it.
Explore groundworks for drivewaysDrainage groundworks
Drainage work is about levels, capacity, access for maintenance and a lawful destination for water or waste.
Explore drainage groundworksExcavation
Excavation work needs a defined depth, safe method, material plan and understanding of what may lie below the surface.
Explore excavationRelated work
View landscapingLandscaping
Retaining, steps, paving and lawn preparation depend on coordinated levels and water movement.
Related work
View extensionsExtensions
Extension setting-out, foundations, drainage and finished floor levels begin in the ground.
Project enquiry
Ask about groundworks for extensions.
Explain what the ground must support and any known access, level, drainage or excavation constraints.