Foundations & Groundworks (Build Stage Guide)

 A practical guide to extension foundations & groundworks: what happens on site, what good looks like, and a homeowner checklist before moving to the next stage.

Stage series note: This is Stage 1 of 9 in our Build Stage Series. Build Stage Series hub.

At a glance - Setting out, excavation, concrete pours and drainage preparation. - Levels and accuracy now prevent expensive fixes later. - A tidy, measured groundwork stage is a sign of a well-run build.

What happens on site (step-by-step for foundations & groundworks)

1. Site set-up and setting-out from drawings (datums + lines).

2. Excavate to the specified depth and width.

3. Pour concrete and allow proper curing.

4. Drainage runs/ICs as required.

5. Prepare for substructure build-up (clean formation, safe access).

Homeowner checklist (screenshot this ■)

■ Setting-out lines match the drawings (including diagonals).

■ Excavation is consistent, clean-edged and stable.

■ Concrete looks well-compacted and level.

■ Drainage falls make sense (no flat/negative runs).

■ Photos taken before backfill (useful for records and future works).

Common mistakes (and how we avoid them)

- Rushing setting-out → Walls end up out of square. We do this instead: We double-check diagonals and datums before digging.

- Pouring on soft/loose formation → Settlement and cracking risk. We do this instead: We keep formation clean, stable and pour promptly.

- Not planning access → Delays and safety issues. We do this instead: We plan material drops, spoil location and safe walkways.

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Planning a build in Suffolk, Essex or Cambridgeshire? Get in touch with K N Construction to discuss your project.