Strip foundation excavation

Strip foundation excavation is the dig to formation for linear foundations under walls — including trench-fill variants where the engineer specifies concrete filling most of the trench.

This is a construction-process page: widths, depths, and concrete grades come from drawings. Frost and clay depths are design decisions explained on the frost-depth and ground-conditions guides.

review Groundworks Contractors in Wandsworth and Groundworks Contractors in Kingston.

When sequence matters

When setting out new housing or extensions on strip/trench-fill foundations; when planning trench support and spoil routes; or when Building Control inspection is required before concrete.

Typical sequence

Step 1: Set out
What this step delivers: Lines and levels established.
Step 2: Excavate to formation
What this step delivers: Width and depth achieved safely.
Step 3: Inspect
What this step delivers: Formation accepted.
Step 4: Concrete
What this step delivers: Placement to specification.

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What each stage delivers

Set out centre lines, excavate to the specified width and founding level, trim formation, manage water and trench stability, and prepare for inspection. Hand dig may be required near services.

Do not over-dig casually: overbreak and soft spots need engineer instruction (blinding, deeper dig, or local improvement).

Programme risks and hold points

Strip or trench-fill noted on structural drawings
Services crossing trench lines
Wet or unstable trench sides
Steps in foundation level along the wall line
Building Control foundation inspection required

Pre-start and handover checklist

Latest foundation drawing
Service locations confirmed
Trench support / batter plan
Inspection booked
Concrete and disposal arranged

Keeping trades coordinated

Hold for inspection as required, place blinding if specified, then concrete. Record levels and inspection outcomes.

Where time and cost usually escalate

Depth increases, support, wet trenches, and disposal dominate. See excavation cost drivers and foundation cost pages for budgeting links.

Frequently asked questions

How wide and deep should strip trenches be?

Exactly as the structural drawing specifies. Depth may reflect frost, clay, or bearing requirements set by the designer.

How This Issue Is Normally Diagnosed and Repaired

Follow the typical path from problem identification through to resolution:

We provide these services across the UK, including

London Richmond Chiswick Wimbledon Kingston Fulham Hammersmith Ealing

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Have strip foundation drawings? Request an excavation and concrete quote.

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