Underpinning a party wall under the 1996 Act

Party wall underpinning is caught by section 2 of the Party Wall etc. Act 1996, which lists the right to underpin, thicken or raise a party structure among the works a building owner may carry out after serving notice. Excavation close to a neighbour's foundations is caught separately by section 6. Most basement and deep foundation projects engage both, and the notice periods differ, so the sequence matters more than people expect.

None of this is planning. The Act is a private law code governing rights between neighbouring owners, running alongside planning permission and building regulations approval without replacing either. A party wall award does not permit development, and planning permission does not authorise work to a party structure.

When the Act is engaged

Three sections do the work, and a single project can trigger all three.

Section 1 covers building a new wall on or astride the line of junction where nothing is built there now. Notice period: one month.

Section 2 covers works to an existing party wall or party structure, including the works listed above, cutting into it to take a beam, demolishing and rebuilding it, and removing chimney breasts from it. Notice period: two months.

Section 6 covers excavation near a neighbour's building. It applies where you excavate within 3 m of a neighbouring structure to a depth lower than the bottom of their foundations, and where you excavate within 6 m and the excavation would cut a line drawn downwards at 45 degrees from the bottom of their foundations. Notice period: one month.

Deepening a party wall to form a basement therefore needs a section 2 notice, and the excavation alongside it needs section 6 notices to every affected neighbour, including those to the rear and across a side passage. Serve them together and work to the longer period.

Notices, timescales and consent

A notice must identify the building owner, describe the proposed work, and state the date on which it is intended to start. A section 6 notice must also state whether the building owner proposes to strengthen or safeguard the adjoining owner's foundations, and must be accompanied by plans and sections showing the site and depth of the excavation.

Serve on every adjoining owner. That means freeholders and leaseholders with an unexpired term over a year, which in a converted terrace can be four or five people for one wall.

The adjoining owner has 14 days to respond. Consent in writing ends the process for that owner and no award is needed. Silence for 14 days means a dispute is deemed to have arisen, as does a written dissent. There is no penalty for dissenting and most surveyors advise adjoining owners to dissent as a matter of course, so plan on an award rather than hoping for consent.

Starting work without serving notice is the expensive mistake. The remedy available to the neighbour is an injunction, and a court that grants one can stop a partially excavated site indefinitely.

Surveyors and the award

Once a dispute is deemed to exist, the parties either appoint a single agreed surveyor to act impartially for both, or each appoints their own. Where two are appointed they must select a third surveyor at the outset, who resolves any disagreement between them.

The surveyors are not advocates. A surveyor appointed by the building owner acts under a statutory duty, not as their representative, which surprises clients who expected an ally.

The award settles three things: the right to carry out the work, the time and manner of carrying it out, and any other matter arising out of or incidental to the dispute, including costs. It becomes binding once served, and either party may appeal to the county court within 14 days of service.

Where the works involve structural intervention, the award will usually require the design to be certified by a structural engineer and may set out a sequence for the work. That is where the party wall process and the engineering evidence meet, and the calculations behind it are the same ones discussed in Eurocode 7 and geotechnical evidence.

Schedules of condition

A schedule of condition is not required by the Act. Do not skip it.

It is a dated record, written and photographic, of the state of the adjoining property before work starts, covering the rooms and external elevations that could be affected. It exists to answer the claim that a crack appeared because of your excavation when it was there beforehand.

Three points on doing it properly. Record the interior as well as the exterior, since most disputes concern internal finishes. Note existing cracks with dimensions and a scale reference rather than photographing them loosely. And agree the schedule with the adjoining owner's surveyor and attach it to the award, so its status is settled rather than argued about later.

Where the excavation is deep or the ground is sensitive, monitoring during the works complements the schedule, and the practicalities are covered in movement monitoring during basement construction.

What the award can and cannot control

The award governs the party wall works and matters incidental to them. It can set the method, the sequence, the hours during which noisy work may take place, access arrangements, and requirements for making good.

It cannot grant planning permission or approve the work under building regulations. It cannot resolve a boundary dispute about where the legal line runs, though section 1 deals with building on the line of junction. It cannot deal with a rights of light claim, which is a separate civil matter. And it cannot authorise work to a tree, which remains subject to any Tree Preservation Order.

Nor does it override planning conditions. A planning condition restricting working hours or requiring a construction management plan applies regardless of what the award says, and where the two differ the more restrictive controls in practice. The boundary between the two regimes is set out in party wall matters that are not planning matters.

Costs and who pays

The general position is that the building owner pays, because the works are for their benefit. That covers their own surveyor, the adjoining owner's surveyor, the third surveyor where one is called on, and the cost of making good any damage caused.

Costs can be apportioned differently where the work benefits both owners, for example where a defective party wall is rebuilt, or where the adjoining owner requests additional work or behaves unreasonably in the appointment process.

Budget for more than one adjoining owner. A mid-terrace basement with neighbours on both sides and a rear neighbour within the section 6 distance can involve three separate appointments, each with its own award. An adjoining owner may also request security for expenses before work begins, which ties up cash for the duration.

How this sits alongside planning permission

Sequence the two processes rather than running them together.

Get planning permission first where the scheme needs it, because the party wall notices have to describe the work that will actually be done, and a scheme amended during determination means re-serving. Then serve notices, allowing two months for section 2 and one month for section 6, plus time for appointments and the award itself. A realistic allowance from first notice to award is three to four months where there is more than one adjoining owner.

Discharge the pre-commencement planning conditions in parallel. Structural evidence prepared for the planning application, such as a Structural Survey or a Basement Impact Assessment, usually does double duty in the party wall process, which is an argument for commissioning it properly the first time.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. To see which planning documents a basement or deep foundation scheme is likely to need, enter your postcode on PlanScope.