How Much MOT Type 1 Do I Need? A Practical Aggregate Calculator Guide
MOT Type 1 is a popular sub-base for patios, paths, driveways and small building bases, but ordering it by eye is an expensive way to start a project. The quantity depends on the footprint, the compacted depth, the ground conditions and the way your supplier sells the material. This guide explains the calculation, shows a worked example and walks you through the Handyman Hub gravel and aggregate calculator.
What MOT Type 1 is used for
MOT Type 1 is a well-graded crushed aggregate designed to compact into a stable sub-base. It is commonly used below paving, driveways, paths, shed bases and other hardstanding. Recycled and quarried products can differ in grading, density, moisture and permitted uses, so check the product specification before ordering.
The calculator can work out a quantity, but it cannot decide whether Type 1 is suitable for your soil, loading or drainage. Treat the result as an estimating and ordering aid, then confirm the build-up with the paving or construction guidance for your project.
Measure the area before choosing a depth
Measure only the area that will receive the MOT Type 1. A rectangle is length multiplied by width. For an L-shaped area, split the plan into rectangles. Measure a path, landing, step base or driveway apron as its own section so you can check each figure.
Irregular boundaries are easier to estimate when you draw the outline and divide it into simple shapes. If the width changes, take several measurements and use a sensible average. On a curve, smaller straight sections usually produce a more useful order than pretending the whole shape is a rectangle.
Enter the compacted depth, not the loose pile height
Depth should come from the construction detail, the paving manufacturer’s guidance and the ground conditions. A lightly loaded garden path may have a different build-up from a driveway or a base carrying heavy equipment. Weak or disturbed ground may need excavation and treatment before the aggregate is placed.
Enter the finished compacted depth in metres. For example, 150 mm is 0.15 m. The depth of a loose tipped load will be greater because the aggregate settles as it is spread and compacted.
Worked example: a 6 m by 4 m area
A 6 m by 4 m rectangle has an area of 24 m². At a compacted depth of 150 mm, the basic volume is 24 × 0.15 = 3.6 m³. If your supplier recommends a 15% allowance for compaction, uneven formation and small handling losses, the order planning volume becomes 4.14 m³.
Do not convert that figure using a generic online tonnes-per-cubic-metre number and assume it is exact. Quarried and recycled Type 1 products vary. Give the supplier the 3.6 m³ compacted figure and the allowance you have used, then ask how many tonnes or bulk bags they recommend for their material.
Use the aggregate calculator step by step
- Open the gravel and aggregate calculator.
- Select the units you use on your drawing and with your supplier.
- Enter length and width for each simple section, or calculate each section separately.
- Enter the compacted MOT Type 1 depth only.
- Review the cubic-metre result before adding an allowance.
- Record the allowance clearly and ask the supplier for the product conversion.
- Save the material, depth and delivery assumptions with your project notes.
If your project includes a concrete footing, pad or step, use the concrete calculator for that separate element. MOT Type 1 and concrete have different purposes and should not be combined into one order figure.
Compaction, waste and excavation allowances
Compaction is the biggest source of surprises. A sub-base specified at 150 mm is measured after it has been compacted, while a delivery is loose. Ask the supplier whether its coverage figures refer to loose or compacted material and whether a bulk bag is sold by weight or nominal volume.
Excavation also needs its own check. Remove topsoil, roots and soft spots before measuring the formation. If depth varies across a slope, divide the area into bands and calculate each band separately. A round waste percentage should never be used to hide a poor survey or a drainage problem.
Drainage, falls and access
Plan where water will go before ordering aggregate. A patio or drive should fall away from the building, with thresholds, channels and edge restraints allowed for in the levels. More Type 1 will not correct a blocked outlet or an incorrect fall.
Check how the delivery will reach the site. A tipper load, grab lorry or bulk bag may need different access and storage space. If the material must be moved through a house or narrow gate, include the handling time and keep the pile clear of drains and neighbouring boundaries.
Common MOT Type 1 ordering mistakes
Measuring the whole garden
Use the finished hardstanding footprint, including paths and landings, rather than the entire plot.
Using an unconfirmed depth
Confirm the build-up for the soil, paving, traffic and drainage before putting a number into the calculator.
Mixing sub-base and bedding materials
Type 1, sharp sand, grit, mortar and jointing products perform different jobs. Calculate and price them separately.
Ignoring the product specification
Ask whether the material is quarried or recycled, what grading it has and whether it is suitable for the intended use.
Ordering by bag count alone
Bulk bags vary in weight and size. Keep the cubic-metre calculation and let the supplier confirm the equivalent number of bags.
MOT Type 1 preparation checklist
- Draw and measure every section of the hardstanding.
- Confirm the finished compacted depth and falls.
- Check formation, soft spots, roots and drainage.
- Calculate compacted volume before applying an allowance.
- Confirm the supplier’s tonnes or bulk-bag conversion.
- Plan delivery access, storage, spreading and compaction.
- Keep Type 1, bedding and concrete quantities on separate lines.
For further installation guidance, the Pavingexpert reference library is a useful starting point. Always follow the instructions for the paving system and aggregate you actually choose.
Frequently asked questions
How much MOT Type 1 do I need for a 10 m² patio?
Multiply 10 m² by the compacted depth in metres. Then show the compaction allowance separately and ask your supplier for the product-specific conversion to tonnes or bags.
How deep should MOT Type 1 be?
There is no single depth for every project. Soil, drainage, paving, traffic and local construction practice all affect the correct build-up.
Is MOT Type 1 the same as hardcore?
People often use the terms interchangeably, but products vary. Confirm the grading and specification rather than relying on the name alone.
Can the calculator work out a driveway?
Yes. Measure the driveway in simple sections and enter the appropriate compacted depth for the expected loading.
Should I order extra for compaction?
Usually you need an allowance because the delivered material is loose. Use the supplier’s recommendation and keep it visible in your notes.
Will MOT Type 1 solve standing water?
No. Falls, outlets, drainage and the formation must be resolved first. Aggregate quantity cannot replace a drainage design.
Final supplier check
Before ordering, compare your saved calculator result with the drawing, compacted depth, material specification, allowance, delivery access and supplier conversion. Giving the supplier those assumptions makes the quote easier to check and reduces the chance of running short halfway through the job.
