Architect’s Guide to Party Wall Procedures (Part 2)

Design Considerations

It’s only mandatory to include drawings with one of the three types of party wall notice but we’ve found that adjoining owners are much more likely to consent to works that they understand. It’s therefore good practice to include a set of drawings which illustrate the project as whole but with a focus on those aspects that affect the adjoining owner(s).

Foundations

The notice which must be accompanied by drawings is the one relating to the excavation of foundations and the requirement is very specific – they must include a plan and section showing the site and depth of the proposed excavation.

For party wall surveyors, the most useful section will be through any walls that are to be built either up to or astride the boundaries with adjoining properties. Ideally the plan will include an outline of the foundation but just showing the wall fulfills the requirement.

The final depth of the foundations is generally confirmed on site by the Building Inspector after the works have commenced. Foundation depths are therefore assumed at design stage but the assumed depth (typically 1.0m) must be stated. A scaled section is generally taken to fulfill this requirement but, just in case the adjoining owner appoints an awkward surveyor, I’d suggest that the depth is also added as a note.

The Act provides a right to project a foundation over the boundary but only where that is necessary and, in most cases, it can be avoided by adopting an eccentrically loaded foundation like the one shown below. 

If the engineer believes it is necessary for the foundation to project over the boundary, they should expect to be asked to justify that decision to any surveyors appointed.  

Architects will often avoid providing a section through the boundary and that’s especially so if the adjoining owner has a similar extension and the detail of the foundation to that extension is not known. In an ideal world, a trial pit would be dug and the detail added to the ‘existing’ drawings but that's not always possible of practicable. The alternative is to make an assumption but in the knowledge that, if the reality is markedly different, further agreement will be required from the adjoining owner (or, in the absence of such agreement, authority from the surveyors in the form of an award).

The Introduction to this Guide, which will include an Index, can be found here.

To try and keep this guide as user friendly as possible, we’ve focussed on the most common scenarios, but we appreciate that no two jobs are the same. If you’d like to discuss a specific issue relating to one of your projects, you are very welcome to contact us on 020 7183 2578 or via surveying@peterbarry.co.uk.

We’re also happy to speak directly to clients who require advice on party wall procedures or who require assistance preparing party wall notices.