Technical Booklet N Drainage·Page 24·3.9
Drain penetration through walls or foundations
A drain passing through a wall or foundation must either have at least 50 mm clearance all round, or be built in with flexible joints and rocker pipes on each side.
A drain which passes through a wall or foundation should either – (a) pass through an opening giving at least 50 mm clearance all round as shown in Diagram 3.6(a); or (b) be built in with, on each side, flexible joints within 150 mm and rocker pipes of maximum length 600 mm as shown in Diagram 3.6(b).
Source — /Users/richardhill/Documents/planning-arch-project/data/documents/regional/Technical Booklet N - Drainage.pdf