Dear Inquirer,
Thank you for your email.
Sub sections 6(1) and 6(2) of the Party Wall etc. Act 1996 (‘the Act’) places obligations on the owner of a property (called a ‘Building Owner’ under the Act) who wishes to (a) excavate within 3 or 6 metres respectively and (b) to a depth below the foundations of neighbour’s building or structure (e.g. a boundary wall or garage). These two parameters must apply for the Act to be invoked: the 3 and 6 metre distance between the neighbouring structure and the excavation and the depth of the excavation are not mutually exclusive. The Act will not apply if the Building Owner is proposing to excavate within 3 and 6 metres but he/she has evidence that the neighbouring foundations are deeper than the proposed excavations.
If the Act does apply, then the Building Owner must give at least one month’s notice to the neighbour of the intended work, including whether he/she proposes to do anything about safeguarding the neighbour’s foundations. There will also be an obligation that the excavation work does not damage drains utilised by neighbours which happen to run across and beneath the Building Owner’s land. Ground beams are often used to form a ‘bridge ‘ over any drain passing beneath foundations. This can be specified in the notice or determined by party wall surveyors when drafting a Party Wall Award. It will need to be established if the proposed excavations are within 3 metres of a public sewer as this would require approval from the Local Water Authority prior to works commencing; a ‘Build Over Licence’ may be necessary if the public sewer is passing beneath the extension.
Stephen Cornish PhD, MA BSc is a Director and Fellow of the Faculty of Party Wall Surveyors, a Fellow of the Royal Instition of Chartered Surveyors.