An extension to your house is a great way to get a larger kitchen or open plan layout. The price of this will be drastically affected by how much you spend on the kitchen itself. Before committing to a kitchen, it is worth speaking to local builders as they will be able to get very good discounts from kitchen suppliers, which can help reduce your build cost.
If you exclude the kitchen units, appliances and the floor finish, most builders will price single storey extensions between £1650-£2000 per square metre. This price can escalate depending on the level of finish you require, the complexity of the build, and the design of your extension. If you want a very modern design with large roof lanterns and lots of glazing, this price per square metre will rise to over £2000.
On a typical semi-detached 3-bedroom house, the width is around 6m, and to create a large open plan layout we would recommend a 4m deep extension. This would give you a footprint of 24sqm. At the prices mentioned above, the cost of the build would be £39,500 – £48,000. Within these prices, standard sized bi-folding doors, roof lights or roof lanterns would be included; you would also get a plastered finish inside. Most builders would also include the time to fit the kitchen and floors within this price but would not include the purchase of these items.
The price of these builds will go up if there is a lot of structural work involved, or if you are planning other internal changes or re-decoration of other rooms. If a utility room is being created elsewhere in the house, this can add in the region of £10,000 to the build. A downstairs toilet would be in the region of £5,000 depending on its location and size.