The Party Wall Act 1996 governs building work that affects a shared wall, boundary or structure between adjoining properties. It sets out the specific process that must be followed to protect the interests of both Building Owners and Adjoining Owners. The Act typically applies to loft conversions, basement excavations, building extensions and similar types of construction work in terraced or semi-detached homes. 

But what about building work in the garden? You may well think that a new building at the bottom of the garden would not fall within the scope of the Act, but you could be wrong. Take the example of a homeowner wishing to build a standalone garden office. 

Building a garden office

As a result of the recent lockdowns, home working is now not only far more widespread than ever before, but many people are expressing a desire to work from home permanently, at least some of the time. And with living space in the home under increasing pressure, the creation of an office in the garden is a popular solution.

The good news is that a garden office less than 2.5 metres in height that is used as a home office (as opposed to business premises) is likely to fall within permitted development rights. However, it is always worth checking with the local authority to obtain confirmation that no planning consent is required.

When it comes to the garden, the Party Wall Act does not apply to boundary fences, however it does apply to a garden wall that either abuts or sits astride the boundary line, even if the wall does not form part of any building. It also applies to brick-built sheds, though not timber sheds. And it applies to excavations in the garden near a neighbouring property.

Is Party Wall Notice required?

The Party Wall Act states that any work that could affect the structural integrity or support function of the party wall or structure, or could damage the neighbouring side of the wall, must be notified. This includes

• Demolishing and/or rebuilding a party boundary wall
• Increasing the thickness or height of the party boundary wall
• Excavating within 3 metres of a neighbouring building or structure and to a greater depth than the foundations of the neighbouring building or structure
• Excavating within 6 metres of a neighbouring building or structure and to a depth that is below a 45° downward line drawing from the bottom of the foundations of the neighbouring building.

“The first point to consider is whether there are any shared or adjoining structures within 3 metres of the foundations to the proposed annexe,” advises party wall expert Peter Barry Surveyors. If the answer is yes, and the foundations are deeper than those to the shared or adjoining structure, Notice under section 6 of the Party Wall Act must be served. “If the external walls of the annexe are at the boundary, Notice will need to be served under section 1 of the Act.”

How to serve Notice

For building works in the garden, Notice must be served to all affected adjoining owners, following the process set out in the Party Wall Act. It must include the following details:

• Property address
• Details of property owners
• Full description of the proposed garden construction works
• Proposed start date for the work
• Date the Notice is being served
• Clear statement that Notice is served under the Party Wall Act
• Detailed drawing for any excavations

Furthermore, there are clear timescales to be observed in order to comply with party wall legislation. If the planned works affect a garden boundary wall or excavation, Notice must be served at least one month before the intended start date. Each neighbouring party has 14 days in which to give their written consent, otherwise the Notice is deemed to be in dispute. 

If there is a dispute, the parties can appoint a single Agreed Surveyor, or each party can appoint their own surveyor, who will determine a fair and impartial Party Wall Award in line with their statutory responsibilities. Once you have agreement, all works carried out in the garden must comply with the Notice.

Clearly, as with any building work affecting neighbours, it is best practice to reach a friendly agreement in the first instance, regardless of whether Notice needs to be served for the creation of a garden office. In the interests of continued harmonious neighbourly relations, it is advisable to informally discuss the intended works, consider the neighbours’ comments and amend the plans if at all possible, before serving formal Party Wall Notice.