Two numbers for the same repair. One is a supply quote from a manufacturer; the other is an installed price from a contractor. They are not comparable, and treating them as though they are is the most common error in erosion procurement.
What each covers
Supply-only. The product, delivered to a stated point. Sometimes with documentation, sizing guidance, and technical support. It does not include placing anything.
Our quotes are supply-only, and what a quote includes sets out exactly where the boundary sits.
Installed. Product plus labour, plant, and the work of placing it, priced by a party who takes responsibility for delivering the finished installation.
Design and build. Adds the design responsibility. Rare on small erosion work, common on larger schemes.
What falls in the gap
Between a supply price and a finished installation:
- Fill stone, procured and delivered. For bagged armor this is a substantial separate item — see when local stone changes the economics
- Filter layer material and placement
- Subgrade preparation, if the system needs it
- Plant and operators
- Crew
- Access construction, where needed
- Site management — traffic management, welfare, security
- Environmental controls — silt curtains, turbidity monitoring
- Temporary works, including dewatering if required — see what dewatering really adds
- Survey, setting out and as-built
- Waste and reinstatement
- Insurance and bonds
That list is why a supply price and an installed price can differ by a large multiple, and why the multiple varies enormously by site. On an accessible site with local stone it is modest. On a site needing a temporary causeway and dewatering it is not.
Risk, which is the real difference
Money follows risk, and the two structures allocate it differently.
Under supply-only, the client or the client’s contractor carries: quantity accuracy, placement productivity, weather and access, ground conditions, damage during handling, and whether the finished installation performs as intended.
Under an installed contract, the contractor carries most of the delivery risk, and has priced for it.
Neither is better. A client with in-house crews and plant frequently does better buying supply-only, because they are carrying risk they are equipped to manage and not paying someone else to hold it. A client without that capability is usually better buying an outcome.
What does not work is buying supply-only, having no plan for the rest, and discovering the gap after the material arrives.
Identifying which you are looking at
Ask each proposal:
- Does this include placing the material?
- Does it include fill stone? For any bagged system this is the biggest single gap.
- Does it include the filter?
- Does it include plant and crew, and for how many days?
- Does it include temporary works?
- Who is responsible if the installation does not perform?
- What is the basis of quantity, and who carries the risk if more is needed?
Question 7 is worth dwelling on. A supply quote priced on an estimated quantity puts the quantity risk on the buyer. If the extent turns out larger — which it frequently does, because the affected footprint is larger than the visible damage — that is more material at the buyer’s cost.
Building an installed cost from a supply price
Where you are self-delivering or managing the contractor directly:
- Start with the supply price for the quantity
- Add fill stone, delivered, with the tonnage from the layout
- Add filter material and placement
- Add plant and crew days at a realistic placement rate for the site
- Add access, if construction is needed
- Add site management and environmental controls
- Add temporary works, if the method requires them
- Add survey and as-built
- Add contingency for quantity, weather, and ground conditions
What drives installed cost covers each item.
The comparison sheet
When proposals draw the line in different places, the only workable approach is a common sheet with a row for each cost above, filled in for every bidder, with a “not included” marked where it is not.
The ranking frequently changes once the sheet is complete, and where it does not, you can say why. How to compare unlike armor bids covers the ten questions that populate it.
Our own position, plainly
We supply product. We are not a contractor and we do not install, and we do not have an installation arm whose margin is hidden in a supply price.
That means our number is genuinely a supply number, and it also means you need a plan for everything else. Where a client does not have one, saying so early is more useful than shipping material to a site with no means of placing it.