What basement construction method is right for my home?

If you already have a basement under your property, then you could opt for a simple basement conversion. If that won’t give you enough space, then you may need to opt for a basement construction method, plus traditional or modern underpinning techniques to stabilise the construction.

Retrofitting is a method of basement construction under an existing house, where no basement exists. The property remains habitable throughout the process and the build can cover the entire footprint of the building or just a specified area. This is the most expensive method and needs careful research to make sure your plans are viable.

With a sub-basement construction, you’re not limited to a single level. This is the construction method used to create the luxury multi-level basements that have dominated the news.

If you prefer not to excavate below the house at all, then open excavation under the garden is a good alternative method of new build basement construction. Fully or semi underground, this is the ideal way to get the maximum usage out of your land and is an easier procedure than a full retrofit or sub-basement build.

Is my property suitable for basement construction?

Before you start any construction methods that will require underpinning, make sure your property is in a good state of structural repair and be clear where the access to the building site will be. If gaining access to the site will have a negative impact on your neighbours, you may have to rethink your plans.

The surrounding geology will also have an impact on the feasibility of your construction plans. Your local building control officer should be able to help. If the water table is high, you may have to abandon your plans altogether, and you should seek expert advice if your existing basement floods regularly. If your basement has damp issues then investigate the cavity drain membrane system which pumps water away from the foundations and make sure the basement will be properly tanked.

Plan carefully

One area of basement construction that you’ll need to pay close attention to is the initial planning and design phase. While it’s easy to get caught up in the details of the actual build, you’ll need to pay attention to the way you want your basement construction to work for you. Will this be a playroom or a living area, or does it have a specific use as a library, gym or home cinema? The decisions you make now will directly affect the way the space is used.

Be clear from the start on the amount of space you realistically need, the headroom you prefer, the location of the staircase, the access points and the levels of natural light. Get it wrong and you’ll have an unloved and underused space that doesn’t have enough natural light or a good flow. Get it right and you’ll create something truly special, with a natural and invisible flow between the old and the new.