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Property Surveying Blog
July 2, 2018

Party Wall Excavations

Written by Bradley Mackenzie

One of the most common questions we are asked here at Berry Lodge is whether a building owner’s excavations are covered by the Party Wall etc Act 1996.  In order to answer this I will be taking a detailed look at the types of excavations that the Act covers, and confirming why these excavations are notifiable to an adjoining owner and their property.

With the majority of the property stock in England and Wales being built around the turn of the century or around the 1930s, these properties tend to have one common characteristic in place.  That is that all of their foundations tend to be towards the shallower end of the spectrum and generally speaking will range anywhere from 100mm to 450mm.  Building Regulations require foundations for new structures to be a minimum of 1m deep, therefore these foundations end up being deeper than those of the surrounding properties, and that is where the Party Wall etc Act 1996 comes into play, with these works being legally referred to as notifiable under the Party Wall etc Act 1996.

With modern construction techniques allowing for a wide and varied range of different approaches to excavations, I thought I would look at some of the most common types that you tend to see on conventional projects across England and Wales.


Mass Concrete Foundations

These are conventional trench foundations, whereby the contractor will dig a trench, usually a minimum of 1m deep and anywhere from 400mm-600mm wide.  The trench will then be filled with concrete forming a foundation and with the structure above, usually a side or rear extension, being built upon that.

These types of foundations are conventional in the sense that you are most likely to find that the majority of structures are built with this type of foundations, mainly because they are straightforward to undertake, relatively cheap and widely known by contractors.


Piled Foundations

Piled foundations tend to be used where the ground tends to be of a more granular type, for example more sandy or gravelly areas.

The foundation itself is dug when a piling rig drives or drills a drill into the ground usually in excess of 3m deep, which is then later filled with concrete and usually reinforced with some type of metal to add strength and stability.

Piled foundations tend to be less conventional for work such as rear or side extensions, however that being said they are becoming more commonly and widely used, generally speaking because they are fairly quick to install, there are specialist contractors that can do these fairly straightforwardly, and finally they are finally strong allowing the structure above to bear significant load onto the foundations themselves.


Raft Foundations

Raft foundations are slightly similar to mass concrete foundations, however rather than the depth of the excavation and trench being 1m deep, a raft foundation will tend to float on the surface of the ground hence its name, a raft.

The trench is usually in the region of 100 to 200mm deep and once dug will usually have timber shuttering to its perimeter with the entire area then being filled with concrete, usually the addition of some form of metal reinforcement is also installed.

The foundation itself is then able to support a structure above and generally speaking is strong and long-lasting.  In my experience I tend to see raft foundations being used less and less these days, as it takes a significant amount of concrete to construct the raft which generally speaking adds to the construction costs, which is something that most homeowners want to avoid.

If you are planning on undertaking excavations to your property, potentially to build a new rear, side or front extension and are unclear if the Party Wall etc Act 1996 will apply to your works, give us a call now and we will happily review your plans and confirm if the Act is applicable and exactly who the Act is applicable to.

We would also be happy to give you a fixed cost quotation and explain a little bit more about the Party Wall etc Act 1996.