What Are Construction Contracts?

Building or renovating a home is one of the biggest investments most people make. Understanding your construction contract is key to protecting that investment. This construction contracts guide will help you navigate the important details and common pitfalls.

Construction contracts are more than just paperwork. They set out expectations, responsibilities, costs, timelines, and how changes will be managed during your build. No matter what type of project you have, understanding your contract can help you avoid confusion, surprise costs, and stress later.

This guide will help you understand construction contracts and what to check before you sign.

What are construction contracts?

A construction contract is a legally binding agreement between a homeowner and a builder that outlines how a project will be delivered. It details the scope of works, costs, responsibilities, timelines, payment structure, and procedures for handling changes during construction.

The contract protects both the client and the builder by ensuring there is a clear understanding of what is included in the project and how the build will be managed.

There are several common types of construction contracts used in residential building projects, each suited to different styles of builds and client preferences.

Types of Construction Contracts

Fixed-Price Contracts

A fixed-price contract means the builder agrees to complete the project for a set price based on the plans, specifications, and selections provided at the time of quoting.

Unless changes are made by the client or unforeseen circumstances arise that fall outside the contract, the agreed contract price generally remains fixed.

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Best suited for:

• Clients wanting greater budget certainty
• Well-documented projects with completed selections
• Standard custom homes and renovations

Advantages:

• Greater clarity around the total project cost
• Easier budgeting and finance approvals
• Reduced risk of ongoing cost fluctuations

Considerations:

• Variations can increase costs if changes are made during construction
• Allowances such as Prime Cost (PC) Items and Provisional Sums (PS) can still vary
• Less flexibility once construction begins

Cost-Plus Contracts

A cost-plus contract means the client pays the actual construction costs, plus an agreed-upon builder’s margin or management fee.

Rather than locking in a fixed total price, the final project cost reflects the actual labour, materials, subcontractors, and site expenses incurred throughout the build.

Best suited for:

• Architecturally designed homes
• Complex renovations
• Projects where selections or scope may evolve during construction

Advantages:

• Greater flexibility throughout the build
• Transparency around actual construction costs
• Ability to make design decisions progressively

Considerations:

• Final project cost is less predictable
• Requires strong communication and trust between client and builder
• Budget management becomes an ongoing process

Key Terms to Understand

Construction contracts contain industry terminology that can feel overwhelming at first. Understanding the key terms can help you confidently review your contract and ask the right questions before signing.

Scope of Work

The scope of work outlines exactly what the builder is responsible for delivering.

This includes:

• Materials
• Construction methods
• Fixtures and finishes
• Site works
• Inclusions and exclusions

A clearly defined scope helps reduce misunderstandings and prevents disputes later in the project.

Payment Terms

Payment terms explain:

• Deposit requirements
• Progress payment stages
• Timing of invoices
• Conditions for payment

Progress claims are typically linked to milestones such as:

• Base stage
• Frame stage
• Lock-up stage
• Fixing stage
• Completion

Understanding when payments are due helps clients manage cash flow and finance approvals throughout the build.

Completion Dates

The contract should outline:

• Estimated commencement dates
• Construction timeframes
• Extension of time provisions
• Practical completion expectations

Weather delays, changes requested by the client, material shortages, and unexpected site conditions can all affect the schedule. It is important to know how the contract handles these delays.

Prime Cost (PC) Items

Prime Cost Items are allowances for fixtures or products that haven’t been selected at the time of quoting.

The labour to install the item is usually fixed, but the final product cost may vary depending on later selections.

Common PC Items include:

• Appliances
• Tiles
• Tapware
• Lighting
• Bathroom fixtures

For example, a builder may include a $90/m² allowance for tiles. If the final selected tile costs $140/m², the difference becomes a variation.

PC Items are common in residential construction and are not usually a problem. However, you should make sure the allowances match the quality of finish you want.

Provisional Sum (PS) Items

Provisional Sums are allowances for works where the full scope or extent cannot be accurately determined at the time of quoting.

Unlike PC Items, PS allowances include both labour and materials.

Common Provisional Sums include:

• Excavation
• Landscaping
• Retaining walls
• Rock removal
• Unknown site conditions

For example, excavation costs can vary significantly depending on soil conditions discovered during construction. Until works begin, the builder may not know whether the site contains stable soil, rock, groundwater, or hidden obstacles.

Due to this uncertainty, a provisional allowance is included until the real costs are known.

Variations

A variation is any change made to the agreed scope of works after signing the contract.

Variations may include:

• Design changes
• Material upgrades
• Layout adjustments
• Additional works requested during construction

Variations can change both the cost and the construction schedule. Review them carefully before you approve any changes.

Contract Exclusions

Exclusions are items that are specifically excluded from the contract price.

These items can surprise clients if they are not reviewed carefully.

Common exclusions may include:

• Council fees
• Engineering
• Demolition
• Landscaping
• Driveways
• Fencing
• External works
• Service authority fees

Ask your builder how to budget for excluded items to avoid unexpected costs later.

Why the Cheapest Quote Isn’t Always Best

When reviewing construction quotes, it can be tempting to focus purely on the bottom-line price. However, the cheapest quote isn’t always the best value.

A lower quote may sometimes indicate:

• Unrealistically low PC or PS allowances
• Missing scope items
• Large exclusions
• Lower-quality materials
• Incomplete documentation
• Underestimated labour costs

This can result in major changes and extra construction costs.

A clear, detailed quote from an experienced builder usually gives you more certainty and a smoother building process than a quote that just looks cheaper at first.

When comparing builders, it’s important to consider:

• Quality of workmanship
• Communication and transparency
• Experience with similar projects
• Documentation detail
• Reputation and trust
• Realistic allowances and inclusions

Building a home is a long-term investment. Choosing a builder you trust, who does quality work and communicates well, is often worth more than just picking the lowest price.

How to Review and Understand a Construction Contract

Before you sign any construction contract, take time to review the details and ask questions if anything is unclear.

Construction Contract Review Checklist

Confirm the scope of works

Ensure all agreed inclusions, finishes, fixtures, and external works are clearly documented.

Review PC and PS allowances

Check whether allowances are realistic for the level of finish you’re expecting.

Understand exclusions

Identify what isn’t included and allow for those costs within your budget.

Review variation procedures

Understand how changes are priced, approved, and documented throughout the build.

Check timelines

Review estimated construction durations and extension of time clauses.

Clarify payment schedules

Ensure progress payment stages are clearly explained.

Confirm insurance and warranties

Check what insurances the builder carries and what warranties apply to the project.

Understand dispute resolution procedures

Review how disputes or delays are managed if issues arise.

Common Pitfalls to Avoid

Signing before selections are complete

The more choices you make before signing, the more accurate your contract price will be.

Focusing only on the total price

A cheaper quote may contain unrealistic allowances or missing scope items.

Overlooking exclusions

Items that are not included in the contract can have a big effect on your total project budget.

Not asking questions

If anything is unclear, ask your builder to explain it before you sign.

Making changes during construction

Making design changes late in the process can cause delays and add extra costs.

Should You Seek Professional Advice?

If you’re unsure about any aspect of your construction contract, consider getting independent advice before you sign.

• Building consultant
• Quantity surveyor
• Independent contract reviewer

An experienced professional can explain contract terms, point out risks, and make sure you understand your responsibilities before construction starts.

Final LRC Custom Builders Thoughts

A construction contract should make things clear, not confusing.

The better you understand your contract, allowances, exclusions, and responsibilities from the start, the smoother your building experience will be.

Choosing a builder who is open, gives realistic allowances, and explains the process can make a big difference in having a successful project and a home you will enjoy for years.

We have written a comprehensive comparison of Cost Plus and Fixed Price Contracts. Click here if you are trying to determine which option is right for you.

Planning a custom home or renovation and unsure where to begin with contracts and pricing?

At LRC Custom Builders, we believe clear communication and transparent pricing are essential to a successful build. Whether you’re comparing fixed-price and cost-plus contracts or reviewing allowances and exclusions, we’re here to guide you through the process with honesty and experience.

If you’re planning a build across the Bellarine Peninsula, Surf Coast, or Geelong region, contact LRC Custom Builders to discuss your project and take the next step with confidence.

Click here to contact us.