Site Works, Services & External Costs

Site Works, Services and External Works: The Costs That Sit Outside the House Price

Start with the project boundary

Ask what the stated house price includes and what sits outside it. The answer may be different for every project. One contract may include a level building platform and basic service runs, while another may exclude site investigation, retaining, utility connection charges, driveway works, landscaping, fencing or excavation beyond an assumed allowance.

The question is not whether an item is normally included. The question is whether it is included in your priced scope, what assumptions apply, and what will happen if the site proves different from those assumptions.

The main cost groups to clarify

Ground, access and structural work

Building Code Clause B1 covers buildings, building elements and sitework that must withstand likely loads, including wind, earthquake and ground movement. [1] That is why site investigation, drainage, retaining and foundation decisions should not be treated as afterthoughts. The appropriate solution depends on the ground conditions, slope, access, water movement, design and engineering requirements.

For a Northland site, practical constraints can include narrow or steep access, wet ground, existing structures, tree roots, rock, clay, delivery space and the distance to available services. None of these automatically creates a problem, but they can change the method, time and cost of carrying out the work.

Drainage is not just a pipe allowance

Building Code Clause E1 requires rainwater disposal and sitework that protects people and other property from the adverse effects of surface water. [2] Ask how roof water, ground water and surface water are intended to move through the site, and where responsibility begins and ends between the house build, civil work and service providers.

Where drainage or earthworks are not fully designed at pricing stage, the quote may use an allowance. That is not necessarily a red flag, but it should be named and explained so you understand what information is still needed to settle the cost.

Retaining and consent checks need care

A retaining wall up to 1.5 metres can be exempt from building consent only when it does not support surcharge or other additional load. Driveways, parking, buildings, pools, other retaining walls and sloping ground can change the position. [3] Always check the specific design and site with the appropriate professional or council rather than applying a height rule in isolation.

Building Performance also notes that some earthworks, higher retaining walls, decks and other site features can need consent. Local planning controls can add further requirements. [4]

Read allowances carefully

Two common terms can appear in construction pricing. A provisional sum is an allowance for work where the final scope or cost cannot yet be fixed. A prime cost sum is usually an allowance for a selected item. Neither term should be treated as a guaranteed final price. Ask what has been allowed, whether labour is included, what assumptions have been used and how differences will be approved.

A useful question list before you commit

• What site investigation, survey or design information is included and what remains to be obtained?
• What earthworks, access and disposal assumptions sit behind the price?
• How are stormwater, wastewater, ground water and surface water being managed?
• Does the quoted scope include retaining, and what design or consent assumptions apply?
• Who arranges and pays for water, power, telecommunications and wastewater connection work?
• Which external works are included now, allowed for, excluded or to be completed later?
• Which items are provisional sums or prime cost sums, and how will the final amount be reconciled?
• Who is responsible for checking council, provider and planning requirements for the specific site?

Building Performance sources

1. B1 Structure, Building Performance
2. E1 Surface water, Building Performance
3. Retaining walls up to 1.5 metres depth of ground, Building Performance
4. Check if you need consents, Building Performance