Driveway sub-base Type 1
Type 1 (often still called DTp1) is the well-graded crushed stone sub-base specified under countless UK driveways, paths, and paved areas. It compacts to a dense, load-spreading layer when placed in the right thickness and moisture conditions. Random “hardcore” from mixed demolition arisings is not the same product.
This page covers supplying and compacting Type 1 for domestic driveway groundworks. Depth decisions sit on the sub-base depth page; drainage and membranes on their siblings. Mainline imports suitable Type 1 (or approved equivalent) and compacts it in layers to the agreed formation — we do not pass off uncertified rubble as Type 1.
review Groundworks Contractors in Wandsworth and Groundworks Contractors in Kingston.
When driveway groundworks need proper preparation
When drawings or quotations specify Type 1 / DTp1 under the driveway; when replacing failed mixed hardcore; or when a surfacing contractor requires a certified granular platform before attendance.
It also appears when clients try to reuse site arisings that cannot meet grading or compaction expectations.
What the build-up usually includes
After formation and membrane (if specified), Type 1 is delivered, spread in layers typically in the order of 100–150 mm loose lifts (follow the site method), and compacted with appropriate plant to a stable, tight surface. Over-wet or over-dry stone compacts poorly — experienced crews manage moisture and reject contaminated loads.
Edges must confine the stone; without restraint, Type 1 spreads and loses thickness at the perimeter. Final levels leave allowance for laying course or asphalt/resin thickness.
Equivalents to Type 1 exist in modern specifications (for example some recycled aggregates meeting the same grading and performance). Use only what the specification allows. Mainline will not compact clayey “hoggin” and call it Type 1. Document hold points for formation inspection before covering where Building Control or the client’s surveyor requires photographic evidence of depth and membrane — cheap insurance on disputed domestic jobs. Document hold points for formation inspection before covering where Building Control or the client’s surveyor requires photographic evidence of depth and membrane — cheap insurance on disputed domestic jobs.
If this matches your project stage, send drawings and site details for a scoped quote — or call to talk through programme and access constraints.
Get an Accurate QuoteConstruction sequence
Step 1: Prepare formation and membrane
What this step delivers: Clean base ready for stone.
Step 2: Import approved Type 1
What this step delivers: Loads checked on arrival.
Step 3: Compact in layers
What this step delivers: Design depth and density achieved.
Step 4: Final level check
What this step delivers: Falls and thickness confirmed.
Failure modes and site constraints
- Specification names Type 1 or DTp1
- Existing mixed hardcore failing under wheels
- Surfacing contractor requires granular platform
- Need for compacted layers to stated depth
- Rejection of contaminated recycled loads
Layer / specification reference
| Material | Typical behaviour | Driveway outcome |
|---|---|---|
| Type 1 / approved equivalent | Compacts dense and stable | Durable platform |
| Mixed demolition hardcore | Variable grading, contaminants | Settlement and voids |
| Single-size clean stone | May not lock as well | Movement under load |
| Clay-bound arisings | Holds water, weak when wet | Rutting and heave |
Site checklist before surfacing
- Product matches specification (Type 1 or approved equivalent)
- Compacted depth agreed
- Suitable compaction plant on site
- Edges confine the stone
- Moisture and cleanliness of loads acceptable
Drainage and edge detailing
Achieve design compacted depth with a true plane and designed falls. Proof-roll where scoped. Hand over a clean Type 1 surface ready for the next layer. Brief the following trade on protection of the completed formation so scaffolding, deliveries, and skip movements do not undo compaction before the wearing course is down.
What changes cost and programme
Tonnage, haulage distance, compaction time, and waste from rejected loads drive cost. Thin layers that rut immediately waste the material budget. Rate intent: costs hub. Certified Type 1 costs more than mixed hardcore and lasts longer under cars. Constrained London and Home Counties access, permit bay suspensions, and manual handling of stone where machines cannot enter routinely move domestic quotes more than raw tonnage tables suggest. Keep delivery tickets on file with the quote pack so product provenance is clear if settlement is later disputed. Reject loads that arrive saturated beyond workable compaction moisture.
Domestic and shared access contexts
- Standard domestic driveway bases
- Platforms for block, tarmac, and resin
- Replacement of failed mixed hardcore
- Specified landscape and architect build-ups
Frequently asked questions
Is MOT Type 1 the same as DTp1?
In everyday UK site language they are often used interchangeably for well-graded crushed sub-base. Always match the written specification for the job.
Can I compact Type 1 with a car?
No. Use appropriate vibrating rollers or plate compactors in layers.
Do you supply the Type 1?
Yes — supply and compact are normally part of our driveway groundworks package.
How This Issue Is Normally Diagnosed and Repaired
Follow the typical path from problem identification through to resolution:
We provide these services across the UK, including
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Discuss Your ProjectDriveway sub-base Type 1 FAQ
Is MOT Type 1 the same as DTp1?
In everyday UK site language they are often used interchangeably for well-graded crushed sub-base. Always match the written specification for the job.
Can I compact Type 1 with a car?
No. Use appropriate vibrating rollers or plate compactors in layers.
Do you supply the Type 1?
Yes — supply and compact are normally part of our driveway groundworks package.
Need project guidance?
Share your site details and priorities. We will outline a practical scope, likely timeline, and next steps.