How Much Does a House Extension Cost in East Yorkshire? A Realistic Guide

It is one of the first questions anyone asks when they start thinking about extending their home. The honest answer is that it depends, but that is not very useful when you are trying to work out whether a project is worth pursuing. This guide gives you a realistic framework for understanding what drives the cost of a house extension in East Yorkshire.

The main factors that affect extension cost

• Size: The single biggest driver of cost is the floor area of the extension. Larger extensions cost more, but the cost per square metre typically reduces as the project gets bigger because some costs are fixed regardless of size.

• Specification: A single-storey extension in blockwork with a tiled roof and standard kitchen fitting will cost less per square metre than the same footprint built in brick with a flat lantern roof and a bespoke fitted kitchen. Specification choices have a significant impact on total cost.

• Groundworks complexity: Ground conditions vary considerably across East Yorkshire. Sites on the Wolds may encounter chalk or rock. Lower-lying sites may have high water tables or poor-bearing ground that requires deeper or wider foundations. This cannot always be predicted until work begins.

• Existing structure: Connecting a new extension to the existing building requires careful work, including removing parts of external walls, installing structural beams, and managing damp and thermal bridging at the junction. The condition of the existing building affects how straightforward this is.

• Services: Extending heating, plumbing and electrical services into the new space adds cost. If the existing boiler cannot handle the additional load, it may need upgrading.

Rough cost guide for East Yorkshire in 2026

As a rough guide, a single-storey rear extension in East Yorkshire is likely to cost somewhere in the range of £1,800 to £2,500 per square metre for a mid-specification build, including groundworks, structure, roof, windows, external and internal finishes, and basic services connections. Higher-specification finishes, structural complexity, or difficult ground conditions will push that figure higher.

A two-storey extension will generally cost less per square metre than a single-storey extension of equivalent floor area, because the foundation and roof costs are shared across two floors.

What is not included in most extension quotes

• Architect or designer fees

• Planning application fees

• Structural engineer fees

• Building regulations fees

• Party wall surveyor fees where applicable

• Kitchen, bathroom or fitted furniture supply

• Decoration

Getting an accurate quote

The only way to get an accurate figure is to have a builder visit the site, understand the full scope of what you want, and price accordingly. At Harlands Builders we visit every project before quoting, and we give you a price that reflects the actual work involved. We do not build in margins to cover surprises we have not looked for.