If you’re managing infrastructure or underground utility projects, there’s a good chance you’ve already got a few steel road plates sitting in the yard. They’ve most likely been paid for, still work, and feel like the cost-effective choice. Especially compared to composite plates, which can seem pricey upfront.
But do steel plates really cost less than composite?
At Vanguard, we supply composite plates. We’ve spent years helping contractors evaluate when switching from steel makes sense and when it doesn’t. This article will show you how to calculate true costs, factoring in installation, labour, transport, and wear.
It will break down:
- What composite plates really cost upfront.
- The real cost of using steel, including hidden expenses.
- Where composite plates save you money (and when they might not).
By the end, you’ll have a better understanding of the true operations costs of steel and composite plates and be able to decide which system makes sense for your next trenching project.
What do road plates really cost?
Let’s cut to the chase. Composite plates do cost more up front, but that’s just the first piece of the puzzle.
If you’ve ever had to move a 550kg steel plate just to cover a small trench, you already know the cost isn’t just what’s on the invoice. Labour, gear hire, traffic delays – they all eat away at your margins.
To keep things practical, let’s look at a typical scenario: covering a 1200mm wide, 4-metre long trench across a single traffic lane.
Composite plates: Around $9,000 for eight interlocking 2300mm x 500mm modules.
Image: Composite road plates covering a 4m road trench
Steel plates: Around $3,000-$4,000 to purchase (you’ll need four at 2400mm x 1200mm x 25mm), or around $85/week to rent per plate.
Image: Steel road plates covering a 4m road trench (Source: HVR MAG)
Upfront costs are only the first part – let’s look at the less obvious operational costs.
The hidden costs contractors often miss
If you’re still using steel plates because they feel ‘free’, consider these costs that aren’t on the invoice:
- Labour hours for loading, unloading, and installation.
- Machinery required (Hiabs, diggers, or trucks with cranes).
- Asphalt or cold mix to ramping steel plate edges.
- Site delivery and pickup logistics.
- Temporary traffic management while plates are being moved.
Even if you own your steel plates, you are still paying in time, crew hours and risk.
Steel vs composite: A real-world cost breakdown
Once you’ve bought your plates, you still need to install and remove them. That’s where operational costs start adding up and steel gets expensive fast.
For that same 4m trench job, here’s a set-up and removal comparison:
- Steel plates with asphalt edging: $1,200–$1,500 per job.
- Composite modular plates: $50–$100 per job.
That’s per job, just for setup and removal.
(Naturally, actual costs will vary depending on your crew, gear, supplier, and location. But the gap is consistent across most cases.)
Why the difference? Steel plates require lifting gear, asphalt ramps, crew coordination, traffic management, and hours of time. Composite plates? Two people, 15 minutes, and no machines.
Composite plates slash operational costs by removing the need for heavy gear, asphalt and extended crew hours.
These costs aren’t always obvious, but they show up every time you use the plates. Let’s break these down side-by-side in the table below, excluding purchase or rental price:
Table: Operational Cost Comparison: Steel vs Composite Road Plates.
Why steel plates often cost more than composite
To understand the real difference, you have to look at what’s required to move and install a steel plate. Typically, a single steel plate weighs around 550kg. To place it safely you’ll need:
- A digger or Hiab.
- Certified lifting gear.
- A skilled operator.
- Extra crew to assist.
- Temporary traffic management.
That’s before you even ramp the edges with asphalt. It’s time-consuming, high-risk and gear-intensive.
Handling effort alone is often the biggest hidden cost of using steel plates.
Image: Lifting a 550kg steel plate with a forklift (source: kiwihire.co.nz)
Now compare that to composite modular plates.
Each composite module weighs just 65 kg (for a 2300mm x 500mm section) and can be safely placed by two people in 15 minutes: no machines, no asphalt, no downtime, and far less disruption to traffic and workflow.
Image: Two people putting a composite road plate unit over a trench by hand.
For small trenches, tight sites, or short-duration jobs, the difference in handling effort can drastically change how you plan and execute your work, opening up opportunities for efficiency and faster completion of underground utility work.
How long do steel and composite plates last?
When used within their tested capacity, composite plates can last for years. CityCare Water in New Zealand have been using the same plates for over five years with no performance issues. As long as they’re operated within their guidelines, such as trench widths no greater than 1200mm, and regularly inspected for damage, they perform reliably across job after job.
Each Vanguard composite plate is:
- Tested and certified to handle up to 44 tonnes over a 1200mm trench.
- Designed for repeated use and low maintenance.
- Supplied with rubber edging, eliminating the need to pour asphalt edges.
Steel can last too, as long as it is at least 25mm thick, undamaged and properly maintained. Thinner plates often bend under load, and there’s no standard testing requirement for steel.
Composite plates offer more predictability and consistency over time.
Three ways to replace your steel with composite plates
If you’ve decided that composite plates are the right for your site, how do you pay for them in a way that works for your business?
At Vanguard, we offer three flexible purchasing options:
- Buy Outright (Capital Expenditure / CAPEX)
Best if you use plates regularly and long-term. You own the asset from day one and save on hire, labour and downtime immediately.
- Include in Project Costs
For specific or one-off jobs, treat the plates as a method-related item, much like trench shields and traffic management, and cost them into your project budget.
- Rent-to-own (Operating Lease)
With no large upfront spend, rent-to-own spreads out payments over 6-12 months. After the lease period, you own the plates, with no surprise costs.
Here’s how it works at Vanguard:
- We deliver the plates upfront.
- You pay a fixed monthly lease amount.
- After the agreed time (6-12 months) the plates are yours.
Spreading out the costs makes it easy to upgrade your plates without straining cash flow or CAPEX.
For full details, visit Vanguard’s rental options page.
How long until composite plates pay for themselves?
Many contractors find that composite plates pay for themselves after just a few uses. Why? Composite plates reduce costs through faster installs, less downtime, no need for asphalt edging, and fewer equipment hire expenses and injury risks.
The more you use them, the faster they return on your investment.
How to know if composite plates make sense for your business
If you’re only using plates occasionally, renting steel might make sense. But if road plates are part of your standard work, ask yourself:
- How often will we reuse plates?
- How much time are we losing installing steel?
- Could we reduce machine hire, TTM and labour costs?
- Will this improve crew safety and manual handling?
- How many projects would it take to break even?
Answer those questions and the value of composite plates quickly becomes clear.
CityCare in Auckland switched from steel to composite and reported that composite plates paid themselves off within the first year, thanks to time savings and reduced site costs.
Still unsure which plates to choose?
If you’ve relied on steel plates for years, it’s understandable. They are familiar, usually reliable and already paid for. But now you’ve seen what composite plates can offer: faster installs, reduced labour and long-term cost savings.
Keep in mind: it’s not just about the upfront cost. There’s much more to consider, from installation time and labour to safety, transport, and long-term value.
Whether you’re planning your first trench job with composite or looking to roll them out across multiple crews, Vanguard is here to help you evaluate the numbers and find the best fit for your workflow.
Let’s make your next trench setup faster, safer, and smarter.
