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Property Surveying Blog
Written by Bradley Mackenzie

In this blog post, I am going to be looking at special foundations and in particular how recent Case Law has changed the way these foundations can be approached during the Party Wall and construction process.

Special foundations can often be a sticking or delaying point on Party Wall Jobs, therefore I thought it would be a good idea to look at this topic in a bit more detail to help you avoid being on the wrong end of a potential special foundations issue.

In short, a special foundation tends to apply to underpinning or basement excavation scenarios. Under the Party Wall etc Act 1996, a building owner requires the written consent of an adjoining owner in order to use special foundations on their construction project.

The formal wording of the Party Wall etc Act 1996 confirms a special foundation to be:

“special foundations means foundations in which an assemblage of beams or rods is employed for the purpose of distributing any load”

In practice, this means that any foundation that includes any form of metal reinforcement is deemed to be a special foundation through the eyes of the Act.

This poses a problem, as the majority of engineers these days will design a foundation that is not only strong, but also has a very narrow profile, thereby allowing the subterranean space to be maximised during the course of  the construction works.

In order to be able to achieve a narrow foundation, metal reinforcement is commonly used to add structural stability and strength to the foundation.

While this makes perfect engineering sense, through the eyes of the Party Wall etc Act 1996,  in order for a building owner to be able to benefit from this type of foundation, they would need the written consent of the adjoining owner prior to the agreement of the Party Wall Award.

Effectively this means that if an adjoining owner wanted to be difficult, delay, or cause a potential issue to the building owner, they could simply refuse to give their written consent.

This refusal could then mean that the building owner needs to redesign his foundation to a much thicker profile, which on a smaller property can mean that the added space of the subterranean extension may no longer lend itself to a viable and spacious lower ground floor or basement level.

How can this be you ask?

In order to answer that question, we must look further than the Party Wall etc Act 1996 and to the Act that previously covered works to Party Walls.

The London Buildings etc Act 1939, dealt with foundations and in particular placed restrictions on property builders or developers using grillage foundations. Unlike a modern special foundation, a grillage foundation is a significant and substantial foundation. The foundation itself consists of a grill arrangement of beams which supports a hefty and usually incredibly high loading structure above it.

To put this type of foundation into perspective, the World Trade Centre in New York were constructed using grillage foundations.

I’ve included a drawing of a typical grillage foundation, as you can see the foundation is substantial and significant and in my experience unlikely to ever be utilised in a conventional residential context.

So how did these historic and rarely use foundations find themselves being applicable to basement extensions and other subterranean extensions?

It is my view, that since the Party Wall etc Act’s inception in 1996, the term special foundation has been misinterpreted by Surveyors to now cover reinforced foundations. This has lead to the issue that Surveyors and building owners can often encounter when attempting to obtain the written consent to special foundations from adjoining owner.

Up till 2015, this written consent was often utilised by an adjoining owner as a way of potentially thwarting the neighbour’s proposals for a basement extension. However, in 2015 Case Law and in particular Chaturachinda v Fairholme 2015 changed this.

The judgement in this case saw a building owner able to utilise a reinforced foundation design and meant that his foundation proposal was not only strong, narrow profiled and conventional in the sense of basement foundations, but also didn’t require the written consent of the adjoining owner.

In this case, the building owner was able to overcome the definition and interpretation of a “special foundation” as confirmed by the Party Wall etc Act 1996, by cleverly including a foundation beneath the reinforced underpin/foundation itself.

In practice, this meant that the reinforced foundation beneath the existing foundation was deemed to actually be the outer wall of the proposed basement/subterranean room, and the foundation itself was actually the small pad that this wall sat on (labelled Mass Concrete Foundation above).

The pad is entirely sacrificial and in practice wouldn’t actually add any structural support, strength or help distribute load from the structure above to the ground. However, the introduction of it overcame the misinterpreted wording of the Party Wall etc Act 1996 and meant that the building owner was able to proceed in constructing a subterranean/basement extension with a foundation of their choice.

While this Case Law is a shining gem to a misinterpreted Section of the Party Wall etc Act 1996, it is key to remember that in this particular Case the building owner’s engineering team were able to sufficiently demonstrate that the pad foundation actually had a genuine and bona fide purpose.

Therefore, any building owner, or building owner’s engineer who intends to use the outcome of the Chaturachinda v Fairholme 2015 case, should remember that using the outcome as a way of designing an adjoining owner’s special foundation consent out of the picture, will likely be viewed upon poorly.

This means that the foundation design must have a genuine bona fide reason for it to not be covered by the Party Wall etc Act 1996’s special foundations consent.

There are a few Case Laws within the realm of the Party Wall etc Act 1996, that add the clarity that this one did.

If you’re planning on undertaking a subterranean or basement extension to your property, or are an adjoining owner living alongside a building owner who is about to undertake such works. We would recommend speaking to an experienced and qualified Party Wall Surveyor at the first instance.

Ensuring a well versed professional is on board not only ensures that you’re getting the best possible advice, but can also ensure you are properly protected and given the Party Wall etc Act 1996’s full protection.