The Party Wall etc. Act 1996 (PWeA) in Basement Extensions & Subterranean Development
Basement works are exciting, they offer one of the greatest challenges in respect of their design and construction with advanced structural drawings, critical project planning and onerous regulations. If the basement extension or conversion affects a wall shared with a neighbour (the adjoining owner), the PWeA provides a safe means for the development to take place. Further to the Party Wall Act, Local Councils are placing increasing requirements into the planning application process, among them, Method Statements, Environmental Impact Assessments and Basement Impact Assessments.
One key public concern is that basements are altering the way in which groundwater flows through the substratum or ground beneath the immediate surface. While it is an area of concern, it should not restrict the modest conversion / extension, and perhaps, with careful analysis, the creation of mega basements. Yet another aggravating factor is Fluvial flooding which is becoming an issue particularly in basin areas / river catchment areas, London can be said to be among them. What is required is a more holistic approach to tackling water movement through urban areas and sustainable urban drainage systems are a core component to consider in any public or private design scheme.
It is advisable (and required) that Building Owners or the persons proposing the works serve Notice on their neighbours, the Adjoining Owners, one (S6) and/or two months (S2) prior to the works commencing.
It is strongly advised that there are adequate provisions in place when undertaking basement extensions, their nature lends themselves to souring neighbourly relations very easily.
For the Building Owner I would recommend you serve Notice on your neighbours as soon as the process will allow, for hiccups in the party wall process are the very last thing you want during a time critical project and can easily be avoided. I would also recommend that you and your Contractor enter into a formal construction contract agreement ideally using JCT MW / IM / SBC, this will help safeguard both parties interest and mandate insurance requirements which are helpful for negotiations with Party Wall Surveyors. Typically, this will also require you to appoint a Contract Administrator, traditionally your Architect would fulfil this role; however, Building Surveyors are well suited to design and contract roles and may well be able to assist you as Project Managers / Party Wall Surveyor / Architect / Principal Designer and Contract Administrator. Please Contact Us for more information.
For the Adjoining Owner, depending on the nature of the works proposed, I would recommend you assume dissent to the effect of having a Party Wall Award in place although you can also consent to the works proposed. I would also recommend you exercise your right to seek security for expenses and request guidance from an independent engineer (Advising Engineer) and / or a representative from building control at your local authority, the cost of which will be borne by the building owner. Such engineer will be separate to the design engineer, that is the engineer tasked with the design documentation of the notifiable work.
Appointment of the Surveyor or Surveyors occurs after dissent or dispute has arisen, be wary of surveyors requesting appointment before such disagreement has occurred. The costs associated with the creation of the Award and the reasonable fees charged by the surveyors will generally be borne by the Building Owner.
Should the adjoining owner or neighbour be wanting to make use of the structure, or the wall that is to be “raised downwards”, they will be responsible for the additional cost of the request under s11(5)(a) of the PWeA. Design of the basement should not present any restriction with respect to the adjoining owner’s future plan of their property. Should it do so, the Building Owner who instructed the work (regardless of present title) may be liable to pay the additional cost in the works that the Adjoining Owner is undertaking to their property, the additional cost caused as a result of the Building Owner’s works (for example, a reinforced concrete floor slab may extend beyond the face of the foundation wall and will need to be broken out for the Adjoining Owner’s construction). Similarly, the Adjoining Owner (now Building Owner) is liable to pay for a portion of the cost of constructing of the original wall (built by their neighbour) that they intend to use for their own development.
2. Prospective Legislation:
The Subterranean Development bill
The Permitted Development (Basements) Bill 2013–14
- Is due for it’s second reading in the House of Commons on the 16th May 2015
- Update — 16/05/14 — The bill will make no further progress.
Planning (Subterranean Development) Bill [HL] 2015–2016
- Has had it’s 2nd reading in the House of Lords on the 20th November 2015 | Bill, as introduced | Debates
3. The Adjoining Owner’s Foundations
Should the works be proposed to terraced or semi-detached properties, the adjoining owner’s foundations may well require underpinning and as such, Notice should be served 2 months prior to the works commencing. The Adjoining Owner is expressly given by the Act under S6(3) the right to request that the Building Owner and at the Building Owner’s expense, underpins the Adjoining Owner’s foundation insofar as is necessary to retain the right of support.
4. Special Foundations
Although the PWeA expressly states under S7 (4) that “Nothing in this Act shall authorise the building owner to place special foundations on land of an adjoining owner without his consent in writing.” That is in the case of special foundations, so should consent not be received, the use of S2 of the PWeA will move the resolution process forward, a careful design process will also facilitate the issue. Where planning has been approved it is advisable that the Adjoining Owner consents to the use Special Foundations, the PWeA is often criticised in it’s ability to cope with basement construction; however, the consent mechanism does provide a means to achieve subterranean development.
5. The Construction (Design & Management) Regulations 2015 (CDM 2015)
- You must appoint a Principal Contractor and Principal Designer, in writing, where there is more that one Contractor involved on the project.
- You most notify the HSE where:
a) the construction work will last longer than 30 working days and have more than 20 workers working simultaneously at any point in the project; or
b) exceed 500 person days
Generally your Principal Designer (Architect or Chartered Building Surveyor) will make you aware of your obligations under CDM 2015 and serve notification; however, it is critical you bear the above points in mind and ultimately have an appreciation of the regulations and what they mean for you.