Pre-Construction Checks Before Starting a Build in London

The most expensive problems in a renovation or extension project are the ones discovered after work has started. Thorough pre-construction checks — before contracts are signed and spades go in the ground — are the best insurance against costly surprises.

1. Title and Planning Confirmation

Land Registry title register: Confirm ownership, check for covenants, easements, or restrictions in the title that affect what you can do with the property. Rights of way across the plot, drainage easements, and restrictive covenants (particularly in right-to-buy properties) can all affect construction.

Planning permission status: Confirm that any required planning permission is granted and valid (not expired) before starting. Check that all pre-commencement conditions are discharged.

Listed Building Consent: If the property is listed, confirm LBC is in place before any works begin.

Building Regulations application: Confirm the Building Regulations application is submitted and initial approval (full plans approval) or initial notice (approved inspector) is in place.

2. Party Wall Status

If the project affects a party wall or is within 3m or 6m of a neighbour's foundations (depending on depth), the Party Wall etc. Act 1996 applies. Before work starts:

• Party wall notices must have been served on all adjoining owners
• The statutory notice period must have elapsed (at least 1 month for most party wall notices, 2 months for foundation notices)
• Either: written agreement (party wall agreement) has been reached; or a Party Wall Award has been issued by the party wall surveyor(s)

Starting notifiable works without a completed party wall process is a statutory breach. Party wall disputes mid-construction are very costly and can result in injunctions.

3. Drainage and Sewer Check

Thames Water build-over: Any building works within 3m of a public sewer may require Thames Water's consent (or Build Over Agreement) before starting. Check the sewer maps via Thames Water's sewer records and obtain consent if required.

Drainage survey: If the project affects existing drainage or ground conditions near known drains, a CCTV drain survey before starting confirms the condition of existing drainage before it's disturbed.

4. Asbestos Survey

For any property built before 2000, an asbestos Refurbishment and Demolition (R&D) survey is required before any works that disturb the fabric of the building. Do not assume — survey first.

5. Structural and Site Assessment

Load-bearing wall identification: Before removing any internal wall, confirm its structural status. A structural engineer's preliminary assessment of which walls are load-bearing avoids dangerous assumptions.

Ground conditions: Where extensions require new foundations, the assumed ground bearing capacity must be verified — either by reference to previous foundation records or by a trial pit. Clay soils (prevalent in much of London) present specific heave and shrinkage risks.

6. Services Location

Before groundworks begin, mark out the routes of all underground services — gas, electric, water, telecom, and drainage. Contact Dial Before You Dig (digsafe.co.uk) and request utility maps. Striking a live gas or electricity service during excavation is a serious safety incident.

7. Neighbour Notification and Site Access

Inform neighbours of the programme before starting. Agree any requirements for scaffold, skip, skip permit (required for skips on the public highway), and site access. Apply for any highway licences required (scaffold, hoarding, skip).

RCB Design & Build

RCB Design & Build manages pre-construction checks as part of the principal contractor service — ensuring all statutory, legal, and site-preparatory requirements are in order before mobilisation.