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Groundworks · t · bags

How much MOT Type 1 do I need?

MOT Type 1 or scalpings to a finished compacted depth. Order it by weight — the loose heap that arrives is about a quarter bigger than the hole it ends up filling.

Measure it

Every box has its own unit next to it.

Check the rates

Rates and assumptions used

These are the figures the calculator works to. Change any of them and the order list updates — your merchant’s pack sizes and your own waste allowances beat the defaults every time.

How this one works

The figures the calculator works to. Every one can be changed in step 2, and your merchant’s pack sizes and your own waste allowances beat these defaults every time.

RateDefaultWhy
Compacted density2.1 t/m³MOT Type 1 compacted. Scalpings run about 1.9, recycled Type 1 nearer 1.8.
Loose-to-compacted factor1.25Loose material shrinks by roughly a quarter when it is whacked down.
Bulk bag weight0.85 tA standard merchant bulk bag. Some sell 0.8 t, a few sell a full tonne.

A worked example

With the defaults the page opens on:

  • How long is the area? 10 metres
  • How wide is it? 4 metres
  • Any odd bits to add on? 0 square metres
  • How deep once compacted? 150 millimetres
  • Spare for waste 5 per cent

Sub base

  • Area: 40 m² — L × W + extra area
  • Compacted depth: 150 mm
  • Compacted volume: 6 m³ — area × depth
  • Waste allowance: 5 %
  • Order weight: 13.23 t — volume × 2.1 t/m³, +5%
  • Bulk bags: 16 bags — 13.2 / 0.85 tonnes a bag
  • Loose volume delivered: 7.5 m³ — × 1.25 — leave room for the heap

Change any figure above and every line recalculates; the small print under each row is the sum that produced it.

Questions people ask

How many tonnes of Type 1 per square metre?

At 150 mm compacted depth and 2.1 t/m³, about 0.33 t per square metre before waste. The calculator multiplies area by depth by density and adds your waste allowance.

What depth of sub base do I need?

The hints in the calculator give the common figures: 100 mm for a footpath, 150 mm for a drive, 250 mm or more for vehicles over 3.5 t. The right depth for your ground is a design decision; this works out the quantity for the depth you choose.

Why is the delivered heap bigger than the hole?

Loose material compacts by about a quarter when it is whacked down. The calculator shows the loose volume you need room for as well as the compacted volume you are paying to fill.

How many bulk bags is that?

The order weight divided by the bag weight, rounded up. The default is a 0.85 t bag; some merchants sell 0.8 t, a few a full tonne - set it to what yours sells.

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