Overview
Question: Can a building owner cast a new concrete foundation next to an existing foundation and connect the two with dowels, sometimes called overpinning, without serving notice under the Party Wall Act?
In many cases, the act of casting a new foundation next to an existing foundation and dowelling into it will not, by itself, require a party structure notice under section 2 of the Party Wall etc. Act 1996. The reason is that the Act's definition of a party structure does not usually include the foundation below the wall.
However, that does not mean notice is never required. The overall work must still be checked under sections 1, 2 and 6.
Why section 2 may not apply
Section 2 gives rights to carry out certain work to a party wall or party structure. It includes rights such as cutting into a party wall and cutting away projecting footings in certain circumstances.
A foundation is not normally treated as the party structure itself. On that basis, simply casting a new foundation alongside an existing foundation and connecting it with dowels may fall outside section 2.
The important section 6 caveat
Even if section 2 does not apply, section 6 may apply if the work involves excavation:
- within 3 metres of an adjoining owner's structure and to a lower depth than their foundations; or
- within 6 metres where the proposed excavation cuts a plane drawn downwards at 45 degrees from the underside of the adjoining owner's foundations.
If section 6 applies, an excavation notice is required even if the dowelling or overpinning itself is not notifiable under section 2.
Engineering still matters
The fact that work may not require a party wall notice does not make it good practice. The building owner still needs proper structural design, building control approval where required and competent construction.
If the new foundation affects the stability of the adjoining owner's property, the risk may be significant even where the Party Wall Act does not provide a direct route.
Conclusion
Overpinning or dowelling into an existing foundation does not automatically require a party structure notice, because the foundation is not usually the party structure. However, excavation notices under section 6 may still be required. The safest approach is to check the whole project, not just the dowel detail.