Party Wall Appointment
Amersham HP7
(Buckinghamshire Council)
Close to, Chesham, Beaconsfield and Berkhamsted. Within the catchment of our High Wycombe office.
Background: The works involved the removal of the existing rear extension situated behind the garage and which formed a continuum with it, with a new, longer and higher rear extension.
We were appointed by the building owner. The adjoining owners did not wish to appoint the building owner's Surveyor as Agreed Surveyor and instead appointed their own Surveyors, resulting in the involvement of three Surveyors.
There were two adjoining owners
The works involved the erection of a ground floor extension to the rear which involved the excavation for foundations of a new flank wall running parallel to the existing flank wall of the garage.
Conclusion:
The building owner's house was semi-detached. The works involved excavations within 3 m of both adjoining owners and on one side only involved interference to a party wall i.e., the shared garage wall which separated the two garages.
Behind the garages, the building owner had an existing extension of circa 3 m length (pictured from the adjoining owner's side of the boundary).
The building owner's original proposal was to demolish all the walls of the existing extension and re-build it wholly on the building owner's line, positioned as offset from the boundary line.
This posed a problem though, because the existing extension's flank wall was situated wholly on the adjoining owner's side of the boundary, offset from the boundary line by about 6 cm. Hence, the removal of this wall was contingent on the adjoining owner's permission which he did not provide. It was therefore necessary to maintain the flank wall and this created a challenge as the foundation excavations of the proposed new flank wall alongside the existing flank wall could undermine the structural integrity of the existing wall.
The recent removal of large trees in the vicinity and likely subsequent heave this had caused, also had to be factored into the foundation design.
A trial pit was therefore excavated before foundation works were undertaken in order to determine the clay content of the soil. This in turn fed into the design of the foundation depth of the proposed flank wall and also the permitted bay lengths of the hit-and-miss sequenced foundations. The contractor's Method Statement and the engineer's Letter of Comfort were included within the Award's Appendix.
Another aspect that needed to be considered was that the removal of the existing extension would result in the removal of the existing drainage channels on the roof at the juncture of the rear pitch of the garage roofs and the existing extension. An architectural drawing Detail showing a newly designed drainage channel at the juncture to replace the existing one, was included with the Award.