How Much Do Groundworks Cost for a House Extension in Beverley?

Typical groundworks costs for a Beverley extension

For a single storey rear extension of around 15 to 25 square metres, groundworks usually come in at £7,000 to £14,000. That is roughly 10 to 20 percent of the total build cost. Larger footprints, two storey extensions with wider foundations, or plots with awkward access or drainage can reach £15,000 to £25,000.

These are realistic ranges rather than fixed prices. Two extensions of the same size on different streets can differ by several thousand pounds, because the cost depends on what is in the ground rather than what is drawn on the plans.

What the price should include

A proper groundworks quote takes the job from bare garden to a finished floor slab ready for the bricklayer. Check that each of these is itemised, as missing items are where low quotes catch people out.

• Site clearance and breaking out old patios or paths: £500 to £1,500
• Excavating and concreting foundations: roughly £120 to £200 per linear metre at a standard one metre depth
• Muck away: £250 to £400 per grab lorry load, and most extensions need two to four
• Brickwork or blockwork up to damp proof course level
• Ground floor slab with hardcore, membrane, insulation and concrete: around £90 to £140 per square metre
• Drainage alterations, new gullies and a soakaway where needed: £800 to £3,000

How Beverley's ground affects the price

Beverley sits where the chalk of the Wolds meets the clay and silt of the Hull valley, so ground conditions change across the town. Towards the Westwood and parts of Molescroft, chalk is often close to the surface. It makes a firm base, and foundations can sometimes be shallower, though it can be slower to dig.

On the eastern side, around Swinemoor, Grovehill and Flemingate, the ground is more often clay or soft alluvial soil with a higher water table. Building control may ask for trenches of 1.2 to 2 metres or more, particularly near mature trees, where clay shrinks and swells with the seasons. Each extra half metre of depth adds concrete, digging time and spoil, typically £40 to £70 per linear metre. Trenches that fill with water may also need pumping.

Drains, sewers and access

Many Beverley homes, especially terraces and semis built before the 1970s, have a shared sewer running across the back gardens. If your extension is within three metres of one, you will need a build over agreement from Yorkshire Water before work starts. Relocating a manhole or diverting a run typically adds £800 to £2,500.

Access matters just as much. In the tighter streets near the Minster and inside the conservation area, there may be no way to get a digger round the back. Spoil then has to be moved by hand or with a micro digger through a side passage, which can add several days of labour. A house with a wide drive and side access will always be cheaper to dig.

Getting a quote you can rely on

The best way to avoid surprises is to deal with the unknowns before the price is agreed. A good contractor will want to visit, lift manhole covers and look at nearby trees. They should also ask for your structural drawings rather than pricing from a photograph.

• Ask for a trial hole to be dug so the foundation depth is based on evidence
• Get a drainage survey if you are unsure where the sewer runs
• Check whether the quote assumes a set foundation depth and what the rate is for going deeper
• Confirm that muck away, building control visits and making good are included
• Keep a contingency of 10 to 15 percent for ground conditions