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Advising Engineers and Security for Expenses in Party Wall Matters: A Practical Guide for Homeowners and Surveyors
Wednesday 21st May 2025
Introduction
Basement conversions and other structural works near shared boundaries are becoming increasingly common, especially in densely populated urban areas like London. These types of projects can pose significant risks to neighbouring properties, and the Party Wall etc. Act 1996 provides a legal framework to manage those risks fairly.
Two key mechanisms that often come into play in complex party wall matters are the appointment of an Advising Engineer and the provision of Security for Expenses. While often overlooked by property owners, these steps can be critical to ensuring that works proceed safely and that both parties are protected in the event of damage or unforeseen issues.
In this blog, we’ll explore what an Advising Engineer does, when one is typically appointed, who pays for their services, and how Security for Expenses works—including typical sums involved and when they might be requested.
1. Advising Engineer – Function, Appointment, and Payment
Function:
An Advising Engineer is an independent structural or geotechnical engineer appointed by the party wall surveyors to provide expert technical advice related to the proposed notifiable works. Their role is not to design or approve the works on behalf of the Building Owner, but to review, challenge, and assess the designs from a neutral standpoint to protect both properties.
The Advising Engineer’s responsibilities typically include:
Reviewing the Building Owner’s engineering proposals, temporary works designs, and method statements.
Assessing the potential impact of the works on the Adjoining Owner’s property.
Advising on the adequacy of structural safeguards and the sequence of construction.
Recommending protective measures or monitoring arrangements, if necessary.
Supporting the surveyors in drafting a technically informed Party Wall Award.
This appointment is especially common in basement excavations, underpinning, or projects involving deep foundations or retaining structures, where the risk to neighbouring structures is more than negligible.
Appointment and Payment:
The Advising Engineer is appointed by the surveyor acting for the Adjoining Owner, not by either owner directly.
They must remain impartial and are expected to offer objective, independent advice.
Their reasonable fees are paid by the Building Owner, as part of the costs incurred in making the award, in accordance with Section 10(13) of the Party Wall etc. Act 1996.
This ensures that the Adjoining Owner has the benefit of independent technical advice without bearing the cost of obtaining it.
2. Security for Expenses – Purpose, Amount, and Typical Costs
Purpose:
Security for Expenses is a provision under Section 12(1) of the Party Wall etc. Act 1996, giving the Adjoining Owner the right to request that the Building Owner deposits a sum of money to cover potential losses or unfinished works.
The purpose of this is to:
Provide financial protection in case the Building Owner’s works cause damage or are not completed.
Ensure funds are available to carry out emergency or remedial works should the Building Owner fail to act.
Minimise the Adjoining Owner's risk in high-stakes projects like basement digs or major structural alterations.
This is particularly important when:
The Building Owner is a small developer or private individual with limited financial resources.
The works are intrusive, complex, or pose a risk of structural movement.
There is no party wall insurance or bond in place.
Amount:
The amount of security to be provided is determined by the appointed surveyors and must be reasonable and proportionate to the nature and risk level of the works.
It is generally calculated based on:
A costed assessment of potential remedial works or reinstatement.
The complexity and scope of the construction works.
Input from a quantity surveyor or the Advising Engineer, particularly for estimating potential repair costs.
Typical Security Amounts for Basement Works in London:
For a single-storey basement in a standard terrace or semi-detached house:
£20,000 to £50,000 is typical.
The funds are commonly held in:
A joint stakeholder account managed by the parties’ solicitors, or
An escrow account held by the surveyors.
Security is returned to the Building Owner upon completion of the notifiable works and once the risk of damage has passed.
Conclusion
The use of an Advising Engineer and the provision of Security for Expenses are essential tools under the Party Wall etc. Act 1996 for managing risk, particularly in projects involving basement excavations or other intrusive structural work. These mechanisms ensure that both parties—especially the Adjoining Owner—are protected, and that any Party Wall Award issued is technically sound and enforceable.
For Building Owners, understanding these provisions early can help with budgeting, programme planning, and avoiding disputes. For Adjoining Owners, they offer reassurance that appropriate oversight and financial safeguards are in place before work begins.
At Tayross Associates Ltd, we specialise in delivering technically robust and professionally administered party wall services. Our team has extensive experience in managing complex residential and commercial schemes, including those involving basement construction and structural alterations. Engaging a qualified team like Tayross at an early stage ensures clarity, compliance, and confidence for all parties throughout the process.
