Cited, not name-dropped

The standards behind our figures

Most calculators name-drop a standard to look authoritative and then use a number from somewhere else entirely. These pages say what each standard actually contains, which of our figures come from it, and — in three cases — where the version everyone repeats online is wrong.

Why these pages exist

There is a pattern in this category: a calculator cites BS 3882 or Clause 803 in its introduction, and then uses a density or a depth that appears in neither. The citation is decoration.

We got caught by the same thing from the other direction. Building these calculators, three standards turned out to say something different from what the internet consensus said — and in each case the consensus was the one costing readers money.

So each page below sets out what the standard says, which of our figures it supports, and what it does not cover. Where we use a trade convention instead of a standard, we say so rather than borrowing authority we have not earned.

The standards

BS 3882:2015 — TopsoilThe 300 mm spread cap, the rooting depths, and the grades that were withdrawn in 2015 but are still quoted everywhere.Widely misquoted SHW Clause 803 — MOT Type 1The actual grading envelope, why BS EN 13285 alone is the wrong citation, and the lift thickness that gets quoted at DIY readers.Cite both ASTM D448 — Aggregate sizesWhat #57 and #8 actually mean, and why open-graded and dense-graded stone are governed by different specifications entirely.Two families

Where we do not have a standard, and say so

Fill dirt has no material standard in either market. It is uncharacterised excavation arisings. Our densities come from published earthwork tables and we label them as planning figures.
There is no primary measured loose density for dense-graded aggregate. A state highway authority states plainly that no universal value can exist, because maximum dry density depends on the source rock. Our figures are trade-typical and the pages say so.
Tile adhesive coverage has no standard figure and we publish none. It is set by trowel notch, tile size and substrate flatness, and the bag states it for that product.
Mortar bulking factors are trade convention, not specification. We use 1.25 and flag it as ours.

A standard we cannot cite is more useful stated as an absence than dressed up as one. Every figure we use is on the sources page with its grade.

Found a citation error? These pages are the ones most worth checking, and the ones where being wrong would be most embarrassing. If a clause number, an edition year or a table reference is off, tell us — we will correct it and say what it was.