The cost of basement conversion in London is £1,500 per square metre. The total price depends on whether you have an existing basement or need a new excavation.
If a basement company need to dig a new basement, you’ll pay £2,500 per square metre.
This cost guide will help you discover how basement specialists price their projects, which will give you an estimate of the total cost of your basement project.
A word from Proficiency, a basement conversion company based in London: nothing beats having an honest construction company by your side. They tell you as it is, even if it means losing the client due to budget. Be careful of the so-called basement expert who easily meets your budget. Will they be around to fulfil their end to fix the snagging, or will they stick with the budget and finish your basement as promised or cut corners behind your back? Or even worse rise the price mid conversion?
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What is the cost of converting an existing basement
The cost of converting an already existing basement starts from as low as £1,500 per square metre. Converting an existing cellar is one of the most common basement conversions.
With that, you can convert your basement to either a bedroom, home gym, home office, or a fully furnished kitchen. You should expect to pay from £1,400 per square metre if you’re converting a wine cellar.
However, you’ll have to pay more for the other options since you also need to consider all the furnishings that should be done. Some of the costs you will incur for your cellar conversion include the following:
- Structural engineer cost – £100 to £200/ hour
- Hiring a plumber – £40 to £60/hour
- Painter and interior designer – £180 to £200/day
- Electrician costs – £45/hour
What is the cost of a new basement excavation
You should expect to pay anywhere from £2,500 to £4,000 for a new basement space underneath your existing home. Unlike the cellar conversion, this is a significantly higher price tag because of the work involved which includes the following:
- Ensuring the basement is damp proof
- Underpinning the walls
- Rerouting any sewers or drains
- Solving problems related to the ground topography
When it comes to what you want to convert your basement to, if you want a simple wine cellar, a complete conversion should cost you up to £2,500 whereas if you’re looking to convert your basement space into something like a swimming pool, or indoor gym, you should expect to pay anywhere from £4,000 upwards.
Depending on the type of basement conversion you choose, there are several additional costs you’ll incur.
Costs for converting a basement
There are several costs that you will incur in the course of your basement conversion project. The contractor you hire should be able to give you an accurate estimation of the expected costs. The table below gives a clear outline of the costs incurred or expected in the course of the project:
| EXPENSE | AVERAGE COST |
|---|---|
| Converting an existing basement | £1,000 to £1,500/ sq. m |
| Digging new basement space | £2,500 to £4,000/sq. m |
| Creating external access | £5,000 to £7,500/sq. m |
| Lowering and underpinning existing basement | £1,500 to £2,000/sq. m |
| Labour costs | £2,000 to £10,000 |
| Engineer’s fee | £1,000 to £2,000 |
| Planning application(if necessary) | £165 to £206 |
| Building regulations fees | £750 to £900 |
| Party wall agreement | £700 to £1,000 per neighbour |
Additional costs for converting a basement
Apart from the costs mentioned above, the other additional costs you will incur during your conversion. Depending on what you intend to convert your basement to, there are several adjustments and changes you might need to make to turn your basement space into something you love. This means additional expenses which we shall detail in the table below:
| JOB DESCRIPTION | AVERAGE COST |
|---|---|
| Wall plastering | From £300 |
| Painting and decorating | From £250 – £600 |
| Fitting a staircase | £3,000 – £5,000 |
| New bathroom suite | £1,500(standard) – £8,000(high quality) |
| Underfloor heating | From £1,500 |
| Hiring a skip | £150 – £300 |
Factors affecting basement conversion costs
While basement conversions are indeed a more cost-effective option to moving out or getting a new house, there are several things that significantly impact the overall costing. Whether you’re converting an existing basement or the need for a new basement excavation is one of those factors you need to bear in mind.
Considering a basement conversion involves creating new living space under the water table level, you need to consider waterproofing which essentially impacts your budget.
The need for light and heating is another thing that will significantly impact your budget. It’s an investment worth considering since you can’t stay in a dark basement. It will also improve the overall value of your property.
The other factors include the following:
- Quality of materials to be used
- Need for additional structural support
- Plumbing and drainage
- Condition of the existing cellar
- New basement flooring and decorations
The average cost of basement conversions is £1,500 per square metre. Costs depend on the project’s complexity, including the need for structural work, plumbing, and electrical installations, with specific features like wine cellars.