Additional Storeys and The Party Wall Act

An amendment to the General Permitted Development Order which allows property owners to add up to 2 further storeys to their property without planning consent came in to force on 30^th December 2020. So does this mean we’re going to see houses all over London being extended upwards despite how incongruous such an extension may look? A scan through the conditions suggests not.

The most important condition, that only properties constructed between 1948 and 2018 are eligible, rules out most houses in London but if you live in a modern property and meet the other conditions it could be worth considering. I therefore thought it would be timely to provide an overview of the party wall implications.

If the house being extended is semi-detached or terraced the works will include raising the party wall(s). The rules state that party walls can only be raised to a height that is 3.5m above the adjoining property (or any other property in the terrace) which limits the extension to a single storey. Raising a party wall is a right set out in section 2(2)(a) of the Act but is subject to serving a Party Structure Notice on any affected neighbours.

Upon receipt of a notice the adjoining owner can either consent, which completes procedures, or dissent, which triggers a dispute. Where a dispute arises, both parties must appoint a surveyor although they can concur in the appointment of a single agreed surveyor. The surveyor(s) produce a party wall award which resolves the dispute and authorises the work but in a way that limits the risk of damage and ensures that the adjoining owner does not suffer unnecessary inconvenience.

There is a right of access over and adjoining owner’s land to raise a party wall although it is subject to 14 days’ notice in writing. If there is an award, it will set out the conditions relating to access including how the adjoining owner’s property must be protected.

What if the adjoining property is converted in to flats? The raising of the party wall is only notifiable to the adjoining freeholder but associated works, such as cutting pockets in to or projections away from the party wall, will also be notifiable to the leaseholder(s) whose demise encompasses the section of party wall that is directly affected.

Adjoining owners have a right to enclose upon the raised party walls in the future should they be inspired to construct a similar extension. You might think it’s unfair that they get to use the wall which was raised at your expense and you’d be right – section 11(11) of the Act requires them to pay a due proportion of the construction costs. This will typically be 50% calculated using the rates applicable when the use is made.

Finally, the materials used to raise a party wall is something of a grey area under the Act as section 2(2)(a) provides no guidance. The Permitted Development limitations require the materials used to be of a similar appearance to those used in the construction of the exterior of the current house but that wouldn’t prevent a part masonry part timber wall from being used. Surveyors will generally only authorise a wall to be raised in its original material as anything else would potentially prejudice the adjoining owner’s future rights i.e. it would not be possible for them to raise a wall further in masonry that had been raised in timber.

I’m not convinced we’re going to see a sudden building boom as everybody in modern houses starts building upwards but it might be a good option for all those owners suddenly in need of a home office.

Illustration included is from the Adams+Collingwood entry to the NLA New Ideas for Housing competition.

Should you require any advice on raising party walls or any other aspect of party wall procedures you’re welcome to contact us on 020 7183 2578 or by email for some free advice.