A basement lightwell can bring natural light and ventilation into lower-ground-floor accommodation.
However, creating one normally involves excavation directly alongside the building and sometimes very close to a neighbouring property.
That makes Party Wall considerations particularly important.
Excavation is the main issue
A new lightwell may require excavation significantly below existing external ground level.
Where this takes place within three metres of a neighbouring structure and below its foundations, Section 6 may apply.
The six-metre provision can also become relevant to deeper excavation in certain circumstances.
Read our Section 6 excavation guide for a detailed explanation.
Retaining structures
Lightwells usually require some form of retaining construction.
A structural engineer may need to design:
- retaining walls;
- reinforced concrete;
- underpinning;
- temporary works; or
- other means of supporting surrounding ground.
Party wall works
Where the lightwell is close to a shared wall, additional works to the party structure may also be required.
If underpinning becomes necessary, Simple Survey has dedicated guidance on underpinning and the Party Wall Act.
Waterproofing and drainage
Below-ground construction also requires careful waterproofing and drainage design.
These technical matters should be considered alongside the Party Wall procedure.
Simple Survey can help
Lightwells can involve more complex structural relationships than their size suggests.
Send Simple Survey the structural and architectural drawings via our Party Wall Surveyor service page before excavation starts.