Party Wall Questions #6

Thursday, 17th March 2011 | by: Peter Barry


A leasehold owner of a ground floor flat proposes to underpin the rear external walls (not party walls) of their property.

What notice(s) should be served on the Freeholder and the leaseholder of the flat above and what part(s) of the Act apply?


This is another question that was raised at a recent FPWS North London forum meeting which I helped to organise. I would welcome the views of other surveyors. If you are a surveyor involved in party wall matters and would like to attend future meetings please email me at and I’ll keep you updated.


The question does not tell us the extent of the leaseholders’ demise but it was assumed that it included the external walls.

Underpinning a party wall is covered by Section 2(2)(a) of the Act but that section only applies ‘where lands of different owners adjoin and at the line of junction the said lands are built on or a boundary wall, being a party fence wall or the external wall of a building, has been erected’. The boundary with the flat above is the floor rather than the wall and the Freeholder’s ‘lands’ are the same as the Building Owner’s and cannot therefore be divided by a boundary wall. Section 2 of the Act does not therefore apply.

The excavation work required to underpin would not be notifiable to either of the neighbouring properties under Section 6(1) as they are more than 3 metres away but is the excavation notifiable to the Freeholder or the leaseholder of the flat above under that section?

Section 6 applies where a Building Owner proposes ‘to excavate … within a distance of three metres measured horizontally from any part of a building or structure of an adjoining owner’.

The excavations are definitely within 3 metres of the Freeholder’s property and the upstairs leaseholder’s flat (remember the Act only refers to the horizontal distance) so if they can be classed as Adjoining Owners notice will be due.

For the Act’s definition of an “Adjoining Owner” we must look to Section 20 – ‘any owner … of land, buildings, storeys or rooms adjoining those of the Building Owner and for the purposes only of section 6 within the distances specified in that section’.

The upstairs leasehold definitely fits that description and the reference to ‘storeys or rooms‘ suggests that the work is also notifiable to the Freeholder under Section 6; on the basis that the upstairs flat forms part of the Freehold.

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