Extensions and loft conversions are where most owners meet the Act for the first time, usually late. The three triggers are cutting into or building off the party wall, building a new wall at the boundary, and excavating within the section 6 distances. A typical rear extension with a loft conversion above can hit all three on one job, and each has its own notice.
Loft conversions
Steels bearing into the party wall, a new opening, raising the wall for a dormer or removing a chimney breast are all notifiable. Trimming a roof and inserting rooflights on your own side is not. The structural drawings answer this in a minute, which is why serving the notice once the design is fixed is cheaper than serving it twice.
Rear and side extensions
Building a new flank wall up to the boundary engages the line of junction provisions, and the foundations under it usually engage section 6 as well. A neighbour who agrees to a wall astride the boundary is giving something up, and their answer changes the design rather than only the paperwork.
Special foundations
Special foundations means foundations with reinforcement, typically a reinforced concrete raft or piled foundation, placed on the adjoining owner's land. The Act requires the adjoining owner's written consent for them, and consent can be refused outright. This is the one place where a neighbour genuinely can stop a design, and finding out at award stage is expensive.
Basements and underpinning
Excavation for a basement almost always engages section 6, and often both the three metre and the six metre tests. These are the jobs where surveyors spend the most time, where monitoring is most often required, and where the schedule of condition matters most.
Questions people ask about party wall extension
Does a loft conversion always need a party wall agreement?
It needs a notice whenever the work touches the party wall, which most loft conversions do. It needs an award only if the adjoining owner does not consent.
What if the neighbour refuses special foundations?
The design has to change. Consent for special foundations on the adjoining owner's land cannot be forced, so engineers usually design around it with a different foundation type.
Is a chimney breast removal notifiable?
Yes, where the breast forms part of the party wall, which it usually does. It also raises the question of supporting what remains above, which is exactly the kind of condition an award deals with.