In this article, we look at the conventional protections that party wall surveyors commonly introduce into a party wall award where a building owner is proposing to undertake a rear or side extension.
In most cases, an extension project will give rise to the need for a section 6 notice under the Party Wall etc. Act 1996. Section 6 notices, often referred to as notices of adjacent excavation, apply where a building owner proposes to excavate to a depth lower than the foundations of an adjoining owner’s structure and within either 3 metres or, in some cases, 6 metres of that structure.
Given that modern building regulations generally require foundations to be taken to a depth of at least 1 metre, and given that much of the housing stock in England and Wales — particularly turn-of-the-century, Edwardian and 1930s properties — was constructed on far shallower foundations, section 6 of the Act will very often apply to rear and side extension works.
Another common trigger under the Act for extension projects is section 1, which gives a building owner the right to build up to the boundary line and, in certain circumstances, astride it. Where section 1 applies, the adjoining owner is also entitled to receive a party wall notice.
So what protections will party wall surveyors typically introduce into a party wall award to reduce the impact of the works and ensure that the adjoining owner receives proper protection? Below are some of the most common and important examples.
Sectional Excavation in Hit-and-Miss Bays
One of the most typical protections relates to how excavations are carried out when they are close to an adjoining owner’s structure.
Where proposed excavations are within approximately 1 metre to 1.2 metres of a neighbouring structure — whether that be part of the adjoining owner’s house, an existing rear extension, a garden room or a boundary wall — party wall surveyors will often require the foundations to be excavated and filled in sectional hit-and-miss bays.
In practical terms, this means that the building owner cannot excavate the full trench in one continuous run. Instead, the trench must be dug and concreted in alternating sections. For example, one metre may be excavated and filled, then a section left in place, then another section excavated and filled, and so on.
This can come as an unwelcome surprise to some building owners and contractors, as it is slower than a continuous trench excavation. Contractors are often resistant to it for precisely that reason. However, it is a very important protective measure. By retaining sections of undisturbed ground between excavated bays, the risk of undermining nearby structures is significantly reduced. This helps preserve support to the adjoining owner’s building throughout the works and lowers the likelihood of ground movement, cracking or damage.
Where extension works are proposed in close proximity to an adjoining structure, this is one of the most common protections you can expect to see within a party wall award.
Access onto the Adjoining Owner’s Land
Section 8 of the Party Wall etc. Act 1996 gives the building owner a right of access onto adjoining land where that access is necessary in order to carry out works authorised by the Act. In the context of a rear or side extension, this often arises where access is required to construct the flank wall along the boundary line.
However, that right of access is never unlimited. Party wall surveyors will usually ensure that access is carefully managed and controlled within the award so that the impact on the adjoining owner is minimised.
For example, temporary Heras fencing or hoarding may be required to screen off the construction area from the adjoining owner’s garden. Protective boards and sheeting may also be required to cover the adjoining owner’s paving, decking or other external finishes in order to reduce the risk of scratching, impact damage or general wear from contractor traffic and building materials.
Importantly, the award will usually limit access to a defined period, often in the region of four to eight weeks depending on the scope of the works. This ensures that the contractor is compelled to complete the flank wall works within a reasonable timeframe and does not enjoy unrestricted access throughout the entire project.
Drains and Shared Pipework
In many terraced and semi-detached properties, drainage arrangements are shared or closely aligned, often running parallel with the rear wall of the buildings. As a result, when a building owner excavates for a rear or side extension, those drains are often encountered.
A well-drafted party wall award will ensure that shared drainage and pipework are properly considered before works begin. In many cases, the contractor will be required to expose such drains carefully, leaving them intact wherever possible and removing the surrounding ground in a controlled and sympathetic manner.
Where necessary, a suitable lintel or bridging detail may then be installed over the drain to ensure that the new extension does not impose additional load directly onto it. Without this type of protection, there is a real risk of cracked, displaced or ruptured drains, which can in turn lead to flooding, blockages, foul water escape or drainage failure.
Party wall awards will commonly include express provisions dealing with these issues so that contractors understand the level of care required when working around shared drainage infrastructure.
Location of the Flank Wall
Where a building owner is incurring the cost of constructing an extension, it is only natural that they will wish to maximise the internal floor area and overall return on investment. One of the most common ways of doing this is by building right up to the boundary line.
A common misconception is that a building owner must always leave a gap at the boundary. That is not correct. Subject to the relevant provisions of the Act, a building owner may build up to the boundary line and, in some circumstances, astride it.
That said, the crucial point is that the proposed extension must not trespass onto the adjoining owner’s land. If any part of the structure extends beyond the boundary — whether foundations, walls, gutters, fascias or roof coverings — this can create significant dispute and may also prejudice the adjoining owner’s future development potential.
Party wall surveyors will therefore often include provisions requiring the contractor to carefully set out and mark the proposed line of the flank wall before works commence. This helps ensure that the extension, including all elements above and below ground, remains wholly on the building owner’s land and does not stray across the boundary.
Why These Protections Matter
These are just some of the typical provisions that party wall surveyors will include within awards for rear and side extensions. While extensions are common projects, they often involve excavation, boundary construction, access, drainage and structural considerations that can pose real risk to neighbouring property if not properly controlled.
A well-prepared party wall award should do more than simply record that works are taking place. It should introduce practical, site-specific safeguards that reduce risk, limit nuisance and help avoid avoidable neighbourly disputes.
At Simple Survey, we have dealt with thousands of extension projects throughout England and Wales and have encountered a wide range of site-specific issues, from mature gardens and neighbouring structures built close to the boundary, through to owner-specific considerations such as pets, children and access sensitivities.
Get in Touch
If you need the input of an experienced and commercially minded party wall surveyor, get in touch with Simple Survey today at team@simplesurvey.co.uk.
Our market-leading fees start from £35 plus VAT for party wall notices and £300 plus VAT for party wall awards, representing a saving of up to 65% when compared with many other service providers in the market.
We would be very happy to assist and advise you.