We get called out to look at other people's driveways fairly regularly. Someone has had a drive laid two, three, five years ago, and it has sunk by the gate, or there is a dip where the car sits, or the edge has splayed out and the blocks are working loose.
In almost every case, the paving itself is fine. You could lift it, clean it and relay it. What has failed is the part nobody looked at when the quotes came in, because it was already buried by the time anyone saw the finished job.
This article is about that part. It is the least glamorous thing we do and the single biggest determinant of whether a driveway is still flat in fifteen years.
What actually fails
A driveway is a structure. It carries a concentrated load — a car weighs between one and a half and two and a half tonnes, sat on four contact patches the size of a hand — and it has to do that through freeze-thaw cycles, saturated ground and repeated turning forces.
When one sinks, it is usually one of four things, and often several at once.
The dig was too shallow. Not enough sub-base to spread the load, so the load reaches the soft ground underneath and the ground moves.
The sub-base was not compacted properly. The stone was tipped in and levelled rather than laid and compacted in layers. It then compacts itself over the following two winters, under your car, unevenly.
There are no proper edge restraints. The paving is free to spread sideways, so it does, and once it starts it accelerates.
Water is getting in and not getting out. Saturated sub-base loses its load-bearing capacity, and then frost expands the water and lifts everything.
Dig depth and why 100mm is not enough
For a domestic driveway carrying cars, we dig out to around 200mm below finished level as a starting point, and deeper where the ground is soft or where there is made ground, clay or an old garden bed under the frontage. That gets us roughly 150mm of compacted sub-base plus the laying course and the paving unit itself.
You will see driveways laid on 75 or 100mm of sub-base. They exist all over the country and some of them survive, because the ground underneath happened to be good. It is a gamble with your money, and it is why quotes vary so much. Excavation and muck-away are a significant part of the cost — a full 40 square metre drive at 200mm generates around eight tonnes of spoil, and that has to be loaded, carted and tipped.
If one quote is noticeably cheaper than the others, the dig depth is the first place to look.
Compaction: the free thing people skip
Compaction costs almost nothing except time, and it is the difference between a stable base and a pile of loose stone.
Sub-base goes in and gets compacted in layers — typically 75mm at a time, each layer compacted with a plate compactor or a roller before the next goes on. Compact 150mm in one go and the bottom half never properly consolidates. It will consolidate later, gradually, under your car, and that is what becomes the dip.
Watch a drive going in. If the stone goes in all at once and the whacker goes over once at the end, you already know how it ends.
Compaction is free. It is time, not materials. Which is exactly why it is the first thing to get skipped when someone has priced a job too keenly. Martin, MAE Landscapes
Edge restraints, the most common single failure
If we had to pick one detail that decides a driveway's fate, it is this.
Block paving has no inherent lateral strength. The blocks hold together through friction and the sand in the joints, and the whole field of paving is held in place by what is around its perimeter. If the edge is not restrained, every car that turns on the drive pushes the blocks outward by a fraction of a millimetre. Over a few years the joints open, sand washes out, and blocks start to rock.
Proper edge restraint means a kerb, edging block or block course bedded on concrete and haunched — concrete brought up the back of the unit to support it. Not sat on sand. Not bedded on mortar with nothing behind it. The haunching is what takes the sideways force.
It is a visible detail once you know to look. Walk down any street and you can identify which driveways will have problems.
Water, the thing that does the damage
Everything above is really about water.
A saturated sub-base loses a large part of its bearing capacity. Water in the base freezes, expands by roughly nine per cent, and lifts what is above it — then thaws and leaves a void. Repeat that through a Merseyside winter and you have a heave-and-settle cycle working on your drive every few weeks.
Two ways to deal with it. Either shed the water — set falls, put in a channel drain across the threshold, get it to a soakaway — or let it through, with a permeable build-up where an open-graded sub-base holds water in the voids and releases it into the ground. Modern practice increasingly favours the second, and the planning system actively encourages it: an impermeable front driveway over five square metres draining to the road needs planning permission, while a permeable one does not.
What you must not do is send it into the road, or worse, towards the house. We have seen driveways laid falling towards the front door.
Water rules, in order of priority
- Never fall towards the house. Ever.
- Never discharge onto the public highway.
- Either drain through a permeable build-up, or to a soakaway or border.
- Channel drain across any threshold, garage door or dropped kerb.
What the standards actually say
Modular paving in the UK is covered by the BS 7533 series. It is worth knowing the shape of it, because it lets you ask a sharper question.
BS 7533-101, published in 2021, is the structural design code of practice, consolidating five older parts into one document. Part 102 covers installation. Permeable pavements now have their own current part, BS 7533-103, published in March 2026, which superseded the 2009 permeable standard — so a contractor citing BS 7533-13 is quoting from a withdrawn document.
Where a driveway has to manage its own surface water, Part H of the Building Regulations is the relevant framework for drainage. You do not need to become an expert in any of this. You just need to ask which standard the build-up is designed to, and see whether the answer is specific.
The six-point quote checklist
Print this, take it to every quote, and ask the same six questions of each. The differences will be stark.
| Ask | What a good answer sounds like |
|---|---|
| How deep are you excavating? | A number in millimetres, usually 200mm+, with a caveat about ground conditions |
| What sub-base, and how deep? | MOT Type 1 or open-graded, 150mm, compacted in layers |
| How is it compacted? | In 75mm layers, plate compactor or roller, each layer separately |
| What edge restraint? | Kerb or edging bedded and haunched in concrete |
| Where does the water go? | A specific answer: permeable build-up, soakaway, or border |
| Is a membrane included? | Geotextile over the formation, yes |
You are not trying to catch anyone out. You are finding out whether the person quoting has thought about the part you cannot see. Anyone who has will enjoy the questions.
Can a sunken drive be repaired?
Sometimes, and it depends entirely on why it sank.
A localised dip from a single soft spot or a collapsed drain run can often be dealt with by lifting the affected area, excavating, correcting the problem and relaying. Block paving is genuinely good for this — lift, fix, relay, and it is invisible.
Edges that have splayed can be cut out and rebuilt with proper haunched restraints, and the field of paving relaid to the new edge. Not cheap, but far cheaper than a new driveway.
What cannot sensibly be patched is a drive that was laid on an inadequate base across its whole area. If the sub-base is 75mm of poorly compacted stone over clay, you are not fixing that in patches. The honest answer is to take it up and do it once, properly — and we will tell you that rather than sell you a repair that fails again in two years.
Real job, Runcorn
Full excavation, compacted sub-base in layers, haunched edge restraints and new block paving to a three-bed semi. Twelve completed jobs with actual costs on our projects page.
Got a drive that has started to move?
Send a couple of photographs and we will tell you honestly whether it is a repair or a rebuild. We would rather turn work down than sell you the wrong one.
Ground conditions around St Helens
We work a fairly small patch, and after thirteen years you learn what is under it. That knowledge changes what we dig.
Much of St Helens and the surrounding towns sits on boulder clay, which is stable when dry and loses strength badly when saturated. On clay we go deeper than the standard, use a geotextile separator without exception, and pay very close attention to where the water is going — because clay does not let it away.
Around parts of Widnes and the Mersey side of Runcorn we see made ground on former industrial land, which is unpredictable. You can dig 200mm and find anything. On those plots we price a provisional allowance for extra excavation and tell the customer up front rather than discovering it on day two and having an awkward conversation.
Older properties in Rainhill, Prescot and Eccleston frequently have driveways laid over what used to be a front garden, with decades of soft topsoil and organic material below. That has to come out. Leave it and it will consolidate under the car for years.
This is one genuine argument for using a local contractor. Not sentiment — knowing what is under the street before the digger arrives.
How long it should take, and when to be suspicious
A typical 40 square metre driveway is five to eight days for block paving and four to six for resin, assuming reasonable ground and no surprises.
Roughly: a day to excavate and cart away, a day or two to build and compact the sub-base and set the edge restraints, a day for haunching to cure, then laying, cutting and finishing. Resin adds a constraint at the end because it needs dry conditions and a base that is properly cured.
If someone quotes you two days for a full driveway, they are not doing the excavation or they are not compacting in layers. Both are quick if you skip them. Speed on this kind of work is not a selling point — it is usually a warning.
Equally, a drive that drags on for three weeks with nobody on site is its own problem. Ask for a start date and an end date in writing, and ask what happens if the weather moves them. Any established contractor will give you both without hesitating.
Related reading: resin or block paving for choosing a surface, and how we build driveways for our full specification.
