Party walls – Eccentric foundations

‘Eccentric foundations’ might sound like a strange term, but it is one that is quite common in the world of a party wall surveyor.

When a building owner serves an Adjacent Excavation Notice on an adjoining owner, eccentric foundations are a popular choice to enable you to build up to or on the boundary line without disturbing the adjoining owner’s land. 

In this article, Harrison Clarke, specialist party wall surveyors, gives you a brief introduction into this type of foundation. 

We explain what eccentric foundations are, as well as why and when they might be used in the construction of a new structure or building.

What is an eccentric foundation?

In construction terms, with

Construction if the foundations of a brick wall.

 traditional or ‘typical’ foundations, the wall will sit on the middle of the foundation. 

However, with eccentric

 foundations – also sometimes referred to as ‘offset’ foundations, the wall will sit on the outer edge of the foundation. 

In layperson’s terms, this means that you can dig the trench for your foundations right up to the edge of the boundary, and the structure or the wall of the building will sit on the outer edge of the foundation instead of at the centre. This enables the proposed construction to stay within the boundary, preventing your foundations from encroaching on neighbouring land. 

When are eccentric foundations used?

When a building owner wants to make the best use of the space within their boundary, it is common to see their drawings propose building up to the boundary line. In this case, eccentric foundations are a sensible option to consider for these works. 

The Party Wall etc. Act 1996 states that you have a right to build up to the boundary of your property and, if necessary, you also have the right to construct foundations on your neighbour’s land. 

Perhaps unsurprisingly, we find that neighbours can often be alarmed at this idea and can initially refuse to grant you permission to build, by dissenting to your Party Wall Notice. 

If your neighbour refuses permission for you to construct foundations on their land, and you cannot prove that this is a necessary course of action, this can cause lengthy delays to your building works. 

Also, any dissent or dispute will inevitably result in your costs escalating. As the building owner carrying out the works, it is normally your responsibility to cover all the costs of both parties’ surveyors, including any additional surveyors or other experts who may need to be brought in to help you to resolve any dispute and get your Party Wall Award granted. 

Going back to the wording in the Party Wall etc. Act 1996, the key phrase relating to constructing foundations on your neighbour’s land here is ‘if necessary’. ‘If necessary’ can be a hard stipulation to prove.

Fortunately, eccentric foundations are a workable, alternative solution for almost all extensions.

It can be hugely reassuring for your neighbours if you can remove any concerns they may have had about you encroaching on and disturbing their land with your building works. 

Choosing to go down the eccentric foundations route therefore helps to minimise any disputes and helps to maintain your hopefully harmonious relations with your neighbours. This is generally an important factor for most people. 

Eccentric foundations are also used if your neighbour has already constructed an extension up to the boundary line, or if their foundations already fall on your land, which could rule out the possibility of laying traditional foundations.

Why should I consider using eccentric foundations?

Although eccentric foundations can be more expensive than traditional options, there are advantages to using eccentric foundations for your extension, which we feel justify the extra cost. 

Using eccentric foundations means that you will own the entire wall if it is built up to the boundary. 

And, to reiterate our previous points, it means that your neighbour is more likely to agree to your building works proposal if your foundations are not encroaching on their land.

Also, they will not be inhibited by your foundations, should they wish to carry out their own extension works. This can help to maintain a good relationship with your neighbour and reduce the risk of any disputes arising, especially if you know that they are keen to carry out their own works in the future.

Will I still a need a Party Wall agreement if I’m using eccentric foundations?

Yes, you will definitely still need a Party Wall agreement. If your excavations are likely to be deeper than the adjoining owner’s, or if you are building up to the boundary line, you will still need to serve notice and follow the proper party wall procedures, complying with the Party Wall etc. Act 1996.

The Party Wall etc. Act 1996 came into force on 1st July 1997 in England and Wales. It acts as a framework to enable development or works that affect party walls to be undertaken, whilst providing protection for the building owner and the adjoining owner.

As well as being devised to prevent building work that could compromise the structural integrity of any shared walls or adjoining properties, the Act is also there to try to mitigate or stop any disputes between neighbours, and to help to resolve disputes if they do arise.

More information

We have a range of videos talking through various surveying services, including party walls. You can access them via our website or our YouTube channel. If we have not covered your query in our videos and blogs, you can’t find what you are looking for, or you would just like to chat things through, please don’t hesitate to get in touch. We would be more than happy to help you.

How you can contact Harrison Clarke

To find out more about how foundation details can affect your party wall processes, get in touch with our friendly, expert and experienced team of qualified building surveyors.

You can call us on 023 8155 0051, or email us at

We would welcome the opportunity to help you with any queries or requests.

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Discover something you would like to know more about?

Faye Williams, party wall and building surveyor at Harrison Clarke chartered surveyors.

About the author

Faye Williams,
BSc (Hons) MFPWS Senior

Surveyor & Winner of Young Property Person of the Year 2023

Faye joined Harrison Clarke in 2018. Faye found an interest in Party Wall surveying, and became a Member of the Faculty of Party Wall Surveyors in 2022.

Since then, Faye has set out a revolutionary approach to party wall instructions, by focusing on people and relationships, backed up by expert knowledge. Faye’s approach has saved building owners £1,000s in unnecessary party wall fees.