Rear infill extensions can create valuable additional internal space, particularly in terraced and semi-detached houses.
Although the design can sometimes look relatively straightforward, the Party Wall implications can involve several different parts of the Act.
Why are infill extensions commonly Party Wall projects?
These extensions are often built very close to neighbouring buildings and boundaries.
They can therefore involve:
- new foundations close to neighbouring structures;
- new walls at the boundary;
- structural work to existing party walls;
- steel beams supported within party walls; and
- alterations to existing rear projections.
One project can potentially engage more than one Party Wall provision.
Our Party Wall Notices in England and Wales guidance gives a useful overview of the different notice types that may arise.
Excavation for foundations
Modern extension foundations are frequently deeper than the foundations of older neighbouring houses.
If your new foundations are within the relevant distance and extend below your neighbour’s foundations, a notice may be required.
Your structural drawings should show the proposed foundation depth.
For more detail on what should accompany an excavation notice, see What Drawings Are Needed with a Party Wall Notice?.
New walls near the boundary
The position of the new external wall is also important.
If it is built at the line of junction, notice may be required.
Whether the wall is proposed wholly on your land or astride the boundary can affect what rights are available.
Our Section 1 guide explains this distinction in more detail.
Cutting steelwork into the party wall
Opening up the back of a house to connect it with a new extension frequently requires structural steelwork.
Where beams are supported within a party wall, this is another common Party Wall consideration.
Our guide to Section 2 works explains how cutting into and altering a party structure is dealt with.
Neighbouring extensions can complicate matters
Many terraced properties already have extensions on one or both sides.
That can affect access, foundations, flashing, waterproofing and the sequence of construction.
Simple Survey can help
Simple Survey regularly acts on rear and side infill extensions throughout England and Wales.
Visit our Party Wall service page or send us your architectural and structural drawings so we can identify the notices required.