Basement development – planning an extension – how to calculate costs

Building an extension for your house can be a great way to upgrade the space and increase the value of any property. The idea of extending out to the garden or up through the roof has been around for a long time now, but now redoing a basement has also come into the picture. There are many ways you could use the new found, underground square meters, from a kids’ playroom to a bedroom, bathroom or a home office. All of them require proper planning, which also means calculating the costs beforehand. How to do it and not spend a fortune?

Consider all factors – costly features of basement renovation

Every basement extension is different and no two projects could ever be the same, especially in London. Many older buildings have basements, which means the space is tere ready to renovate, but some will require serious work including moving the drains, assessing the ground and generally building a whole new structure underground. As of 2019, the range of basement conversion costs varies from £2,000 per m2 to £3,500 per m2 throughout the UK, although some places can charge more, depending on the location. The costs will be affected by many things, starting with the scope of the work that needs to be done. It’s always best to get a professional company in and get a quote for the job before deciding on the final budget.
The price you pay for the job is also highly dependent on the company you choos to do the work. Hiring contractors means you don’t need to find every single specialist yourself and your not held accountable for every job, including getting permits, but you have to pay more for such help. You should also remember that a site survey assessing ground conditions is necessary to properly calculate the overall price of the renovation – it’s not wise to save money here and find out about a drainage or access route that needs to be moved before the basement can be finished.

Basement development is costly and what’s worse, the prices that were mentioned here previously usually cover only the main construction process. When calculating the overall costs, remember that you might need to add extra for fitting out the basement – the electrics, plumbing, a staircase, plastering the walls or laying down the flooring will cost altogether around £900-1000 per square meter.

How to save on basement development

Although it is possible to dig out an entirely new basement and create additional floor space without taking up the garden or extending up, it’s more money-friendly to simply use the existing cellar. It might be smaller than a new built-in, but it will be much cheaper and with proper preparation, can get as cosy as it can be. And if you’re still convinced you want to build a whole new basement, doing so under the garden rather than directly under the house will be a cheaper option too, as you won’t need to worry about changing the foundation of the building.
It’s hard to save when you want your new basement to be safe, complete and durable, which is why many people either give up on the idea or leave the basement unfinished. Our tip? Get a professional quote and use online cost calculators to assess your basic level of budget needed and then try to make changes on things that can be done cheaper. After all, you can do some finishing work yourself, making the price even lower.