What a house extension costs in Kent

Lloyd Lundie Building Contractors build extensions, kitchens and family rooms and the bathrooms and bi-fold doors that usually go with them, from Challock across Kent and the South East. This guide explains what changes the cost, and what a published rate cannot tell you.

What actually changes the price

Two extensions with the same floor area can be very different jobs. These are the things we look at on a visit, because each one changes the labour, the materials, or both.

• Footprint and storeys. A single-storey rear room is a different build from a two-storey extension that also adds a bedroom upstairs.
• Shape. A simple rectangle on the back of the house is simpler than a side extension or a wrap-around that turns a corner and meets two existing walls.
• The ground. Clay, a high water table, drains in the way, or poor access for materials all add work before a wall goes up.
• Matching the house. Brick, roof tile, windows and detailing are chosen so the new work looks as if it has always been there. Unusual bricks or a complex roof take longer to match.
• What the room is for. An empty shell is not the same job as a kitchen diner with units, plumbing, electrics, bi-fold doors and a roof lantern.
• Opening up the existing house. Knocking through into the old kitchen or dining room needs support in the wall you are removing.

What a guess usually leaves out

Online rates are often quoted per square metre and exclude the parts that decide whether the number is useful. Work to an existing home is normally charged VAT at the standard rate, currently 20%, as set out on GOV.UK: VAT rates. Planning fees and building-control fees are set by the council or the building-control body, and they are not part of the builder's labour.

Our extension cost calculator gives an indicative figure, ex VAT, for a single-storey rear, a side or wrap-around, or a double-storey extension. It is a way to see how size and a few extras move the total. It is not a quotation. The quotation comes after a free site visit, and it is based on the work that project actually needs.

We may be beaten on price. The promise we make is on quality, service and care, and on completing the work we have agreed.

Kitchens and bathrooms inside the extension

A new kitchen is often the reason for the extension. A straightforward kitchen fit takes around 2–3 weeks. A kitchen inside a new extension runs with the main build, and a single-storey extension generally takes around 8–14 weeks depending on size and specification. A bathroom refit on its own takes around 1–2 weeks. Those ranges are typical of the jobs we do. They are not a promise for every house.

We hold accounts with kitchen suppliers around Medway and Maidstone, and the full trade discount is passed on to you. You can also supply the kitchen yourself and we will fit it. Either way, a working kitchen stays in use during the build, so you are not cooking in a temporary setup for the whole job. Susan Griffiths in Ashford, who had a single-storey extension, a new kitchen and a relocated bathroom, wrote that they always had access to a working kitchen and bathroom. You can read that review with the others on our reviews page.

How we arrive at a quotation

1. We visit the house, listen to the rooms you need, and look at access, drains, the existing structure and how you want the extension to look.
2. We explain the practical options for that property, including where a smaller or simpler design would save money without spoiling the room.
3. You receive a clear quotation for the work the project requires, with the specification written down so you can see what is included.
4. If the job goes ahead, you get a schedule of what is happening and which trades or deliveries to expect. The workmanship carries a 10-year guarantee.

The same team covers Medway, Maidstone, Ashford, Canterbury, Thanet, Whitstable and the rest of Kent. If you already know you want bi-fold doors or a roof lantern, say so at the start. They belong in the design and the price, not as a surprise at the end.