The fill is the reason bagged armor works economically: the mesh is the engineered element, so the stone does not have to be a quarried armor gradation. See when local stone changes the economics.
That is not the same as “any rock will do.”
The four requirements
1. Larger than the mesh aperture
By a sensible margin, so it stays in. The aperture is set by the weave; the answer bank covers what aggregate gradation fits securely within it.
The consequence of getting this wrong is direct: undersized material migrates out of the unit over time. The unit loses mass, loses shape, and the armor thins.
2. Durable in the service environment
Stone that degrades, slakes, or breaks down in water is not suitable regardless of its size on delivery. A soft sedimentary rock that arrives correctly sized and disintegrates over a few wet-dry cycles produces undersized material inside a unit that started out compliant.
This is a materials question about the specific quarry, not a generic one.
3. Reasonably well graded within the acceptable range
So the unit fills densely rather than with large internal voids. A single-size fill packs poorly; a range within the acceptable band packs better and produces a denser, more stable unit.
The bank addresses whether two approved gradations can be blended within the same bag.
4. Dense enough
Submerged weight is what resists the flow. Lightweight, highly porous, or vesicular material reduces unit stability even at the same volume.
The bank covers how aggregate density changes the filled weight and final dimensions, which matters because a lighter stone produces a lighter unit at the same fill volume.
Angular or rounded
A question that comes up on every job, and the bank answers it directly.
The trade:
Angular stone interlocks within the unit and between units, which improves stability. It also point-loads the mesh from inside, which is what the static puncture (CBR) method addresses. See puncture, abrasion, ice, and debris.
Rounded stone is gentler on the mesh and packs differently, with less interlock.
The bank also covers how sharp, flat, or elongated particles should be evaluated before filling. Flat and elongated pieces are the ones to watch: they pack poorly, they can bridge inside the unit leaving voids, and a thin edge concentrates load on the mesh.
Quarry-run
Whether quarry-run material can be used without additional screening is one of the bank’s questions, and the answer is site-specific.
The risk with unscreened material is the fines. Quarry-run typically contains a wide range including material below the aperture, and the bank covers what problems develop if the fill contains too many undersized particles.
Screening costs money. Undersized fill migrating out of units over decades costs more. Where quarry-run is proposed, the useful step is a sample and an assessment rather than an assumption either way.
Getting local material approved
On agency work this is the process question that matters, and the bank covers it: locally sourced aggregate can be submitted for approval before construction begins.
Doing that early is the difference between a smooth job and a variation. What generally supports the submission:
- Source identification and a gradation analysis
- A durability assessment appropriate to the environment
- A sample
- Confirmation the source can supply at the rate the placement needs
Get it agreed before mobilisation. Discovering at the filling stage that the specified material is not acceptable is an expensive time to find out.
Environmental acceptability
Separate from the engineering. Fill placed in a water body has to be acceptable for that receiving water: not contaminated, not a material that leaches, and consistent with any permit condition.
The bank covers what fill stone is environmentally acceptable, and it is a question a reviewer may ask. See Section 404.
Production control on site
Filling happens at the site or a staging area, which means quality control happens there too. The bank covers how fill volume is checked during production and what filled-weight tolerance is acceptable per size.
Practically, the things worth having in place before filling starts:
- An agreed check on fill volume or weight, and who does it
- A defined frequency for checks rather than a spot check at the start
- A record, since the as-built matters later
- A response if material arriving on site differs from what was approved
What we cannot give you yet
Being straight: the per-size filled weight tolerance and the full dimensional data live in a product data sheet that has not been issued. Five answers in the bank defer to it.
Until it arrives, filled weight and dimensional tolerances come from the engineering team per project rather than from a published table. If your specification needs those figures at bid stage, raise it early. See what a quote includes.
Where to go next
- Site assessment before you order
- When local stone changes the economics
- Filling a rock bag
- What the mesh is made of
- The rock bag FAQ for the full fill-stone section
- The installation hub for the rest