Other Legal Requirements when building a home extension

Party Wall Actlegal requirements

Although a similar act previously existed in London it was not until the 1996 act that it was extended to the remainder of England and Wales. As well as covering the more obvious situation of work on party walls (such as building in a beam as may occur with loft conversions) it also covers foundations and excavations that would be deeper than those of an adjacent property within 3 metres. There is also a rather less common case where new foundations are within 6 metres of another building where a theoretical line at 45degrees is drawn down from the neighbouring foundation (in line with the wall) to the new foundation. This might occur with new basements or particularly deep foundations such as piles.
party wall definition
An actual party wall under the Act is defined as either a wall of a building separating between different owners (irrespective of the actual boundary) or a wall of a building built over the boundary. There could be situations where parts of the wall comply with the definition and parts that do not.


party wall newe foundations
New foundations or excavations The foundations to the extension are to the left in both cases, the neighbouring property to the right, the boundary can be at any point between. Where the new foundations will be below the existing ones (or the 45 degree line in the second case) the Party Wall Act will apply if within the relevant distances. Where the excavation extends closer to the boundary than the foundations, possibly for drains or a retaining wall, the measurement is taken to the edge of the excavation
The legislation is quite balanced in allowing work to be carried out to party walls or the installation of new deep foundations but protects the interests of neighbouring properties. So whilst it is not likely to stop an extension it could cause delays and add to the costs, in reality the legislation is not used as often as it probably should be but ignoring it could risk receiving an injunction, effectively stopping work until it is sorted out
For a straightforward case it just involves obtaining written consent from the neighbour that they agree to the work, if they do, that is basically it (although you would still be obliged to repair any damage etc.). If however, they do not so readily agree then they can appoint a surveyor (at your cost) as well as needing one yourself, this becomes even more complicated if several owners are involved all appointing their own surveyors such as might occur with flats (in theory it is possible to agree to use the same surveyor).
The part of the legislation relating to actual party walls is probably easier to understand when it needs to apply and will in theory include a reasonable proportion of loft conversions to semi-detached and terraced properties where there is work to or items built into the party walls. With the aspects concerning foundations it can be rather less certain, it is often not known exactly how deep extension foundations will be (it is fairly rare for modest sized extensions to have trial holes dug to assess the ground prior to building unless it is an area with known problems). With regards to existing foundations, buildings built within about the last 30 years will generally have them to a similar depth required now. Prior to this it can be rather less certain the further one goes back so it is more difficult to be sure whether the new foundations will be deeper or not, the safe answer is to assume the new foundations will be deeper but his could set into being an expensive process.
Where just building on a boundary line there is a right under this act to build it provided it is solely on ones own land (other than un-reinforced foundations which may cross the boundary), although one month’s notice in writing should still be given. If the neighbour agrees it could be built astride the boundary.


Properties will often have conditions that are incorporated into the deeds; these will generally be from the original landowner or developer although sometimes these may be added to later. In this latter category it is often aimed at householders gaining from possible development potential of the site, such as building another house.
More typically a covenant is either some restriction of activities such as not keeping pigs, allowing access to major services crossing the site (see Building near Sewers) or alternatively requiring consent for significant alterations to the property such as extensions. This will often only be a formality with perhaps just a nominal administration charge but occasionally fairly substantial amounts of money are required, sometimes related to the enhanced value to the property, although why a previous owner should benefit from this is perhaps rather harder to understand.
With some properties or housing estates where there is a distinctive character to its design the purpose of the covenant may be to preserve them from unsympathetic alterations.
It is quite often difficult, particularly with older properties, to establish who the beneficiaries are. They may have died or in the case of companies have ceased to exist. If it is likely that this might cause difficulties when selling the property it is often possible to insure against problems resulting from a beneficiary reappearing in the future, it can also be possible to have covenants removed but these sorts of matters should be discussed with a solicitor experienced in property matters.

Building near sewers

The usual definitions are:
  • Drain:   serves one building
  • Sewer:   serves two or more buildings
  • Public sewer: a sewer owned or adopted by the sewer authority (sometimes known as a sewerage undertaker)
Fortunately most public sewers are located below roads and away from houses but generally all sewers constructed before 1st October 1937 will be classed as public sewers (although a slightly different system occurred in the former inner London boroughs prior to 1965). This will typically include the sewers often found at the rear of older properties, particularly when terraces and these are often known as ‘section 24 sewers’ (although in reality they look little different to any other drainage).
This will often be dealt with at the building regulations application stage as the council is obliged to confer with the sewerage authority where buildings will be within 3 metres of a public sewer. There could be something within the deeds (see Covenants above) which include other circumstances that may require consideration these include:
  • Other main service supplies (e.g. water supplying several other properties) in close proximity.
  • Private sewers, there may still be a requirement to agree the works with the owner (or joint owners) of it.
  • Buildings that might otherwise be exempt.
The purpose of keeping buildings away from sewers is to protect them from loads from the building and leave space for maintenance of sewers. In practice most sewerage authorities will allow buildings closer than 3 metres and in some cases allow buildings to be built over the sewer when other options are not practical, by what are generally known as ‘sewer build over agreements’. This will depend to some extent on the size and depth of the sewer, for large deep sewers it may be necessary to still keep the full distance away. Many sewerage authorities have standard guidance on dealing with minor public sewers although this may still involve providing a CCTV survey and the payment of a fee.
Manholes to sewers (private and public) are generally not acceptable inside a building as they should be readily accessible, for example to clear blockages. A manhole within a building to a drain to a single dwelling is generally acceptable provided it has an airtight cover.
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