When plans are proposed to build a side, return, or rear extension on or close to a neighbouring property, it becomes an emotive subject as to where the outside of the flank wall sits. Building Owners like to maximise the new space internally whereas Adjoining Owners often fear loss of land and encroachment.
The first option is to build a new Party Wall on the Line of Junction and serve the appropriate Notice. This means building half on the land of each Owner or as otherwise agreed. The cost is borne by the Building Owner unless the Adjoining Owner uses it later for a similar extension. Half the cost of the wall and foundation is then reimbursable or in other proportion to its use.
The second option is for the Building Owners to place the extension wholly on their own land up to the Line of Junction. This is a line of length with no thickness taken through the middle of the boundary. The Building Owner can still place footings on the Adjoining Owners land subject to compensation. Alternatively more expensive concentric foundations can be used to avoid any disturbance.
The third option is for the Building Owners to build the wall sufficiently away from the boundary.
These options all seem quite straightforward but in practice, and often for reasons not connected to the Party Wall matters themselves, disputes arise. To resolve them certain considerations have to be taken into proper account.
A straddling wall will become a Party Wall and as such both parties can utilise it. Compensation can be payable to the Adjoining Owner for providing access and loss of amenity or privacy during the works as well as disturbance to patios and plants. In reality it is probably simplest for a protective hoarding or screen to be erected whilst footings are dug; the wall is built and then neatly finished. An allowance is often made for new soft and hard landscaping where disturbed. However Adjoining Owners with no plans to extend themselves often simply resist any loss of land particularly as it may over shadow the garden.
Building wholly on your own land means that it is not a Party Wall structure and as such no compensation is payable under the Act although access is permitted to build it. Determining the Line of Junction can be difficult because the boundary fence may not represent where it is. The notional rule of thumb that fence posts are on your land with the outer face next door may not apply. Disputes can be expensive to resolve particularly with older properties where boundaries have been altered. Thereafter the Adjoining Owner cannot utilise the wall in the future at least without compensation and consent. The outer face of the wall may not be as neatly finished. In both the first 2 options a boundary fence will be replaced by the wall anyway.
The last option leaves that small or wasted gap between mid-terraced and semi-detached houses in particular that eventually becomes neglected; but at least the boundary fence remains.
So which option do you choose? Building Owners probably 1, 2 then 3, Adjoining Owners 3, 2 then 1, Party Wall Surveyors often reach a compromise with 2. Each case is different and never fails to bring its own disputes between Owners to resolve. Some of these are reasonable, others not so; but common sense and impartiality is still the key to these matters.
Guy Gibson FRICS.
Independent PropertySurveying Chartered Surveyor