Original foundations may not comply with section 5 of NZS 3604 which sets out the bracing requirements for foundations. Where new work to the building is proposed, particularly an alteration that involves removing loadbearing walls or adding an extra floor, the existing piles must be checked by an engineer for their adequacy to provide the required support and bracing.
Bracing can be provided by a combination of:
- anchor piles
- cantilevered driven piles
- perimeter footings
- timber bracing between piles.
BRANZ has a bulletin outlining how to upgrade piled foundations. BRANZ research has also confirmed the effectiveness of simple retrofit solutions to strengthen foundations of existing houses on sloping hillsides.