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Step by Step Guide to Basement Conversions

If you’re considering a basement conversion, we’ve put together a step by step guide explaining the different options and what work is needed. Below you’ll find a thorough guide detailing everything you need to know about basement conversions. If you have any questions however or want specific advice about your property, please don’t hesitate to get in touch.

Types of basement conversions

The first step is to decide what type of basement conversion is right for your property.

New basements

New basements apply for new build properties in which they are built into the property as it is constructed. This is the most convenient option, although not necessarily most common. Most basement conversions tend to be retrofit as more people opt to expand downwards and create additional space as opposed to moving.

The type of basement conversion you choose will depend on your needs – what you plan on using your basement space for, and whether you currently have a basement/cellar space.

Retrofit basement

A retrofit basement is an under-house basement. You dig solely downwards within the parameters of your existing building. There are two types of retrofit basement – a full footprint or a half. Full footprint basement conversions expand the entirety of your current property. It adds a full story to your home. A half footprint conversion only takes up half the volume of your home’s square foot ratio. This will be cheaper as there’s less digging and work involved.

Retrofit basements tend to involve building a new basement where the house doesn’t currently have one.

Cellar conversions

A cellar is often a small underground room. Whereas a basement can have windows and be inhabitable, cellars are often used for storage space and they tend to have temperature controls. We can convert an existing cellar into a basement but as the rooms tend to be quite small, there tends to be a certain amount of excavation work involved.

Under garden basement

An under garden basement conversion involves digging out underneath your garden to create space for a larger basement. A lot of garden basements include creating a separate entrance through the garden and installing glass panels in the midst of the lawn to allow natural light into the basement. Under the garden basements are ideal for those who want to create a large spacer than the first story of your house. These type of basement conversions may be most suitable for home swimming pools or separate entrance apartments.

Do I need planning permission?

If you already have a basement and you’re simply refurbishing the interior, you won’t need to apply for planning permission. If you don’t currently have a basement or your cellar is quite small, you will probably need excavation work to achieve your plans and this more than likely will require planning permission. When you consult a specialist, they will discuss your conversion and advise on whether planning permission will be needed.

How long will the conversion take?

It normally takes up to 8 weeks to receive planning permission for a conversion, although more complex projects can take up to 13 weeks. If your basement conversion does require planning permission, you need to bear this period in mind as work cannot commence until this has been sorted. In regards to the conversion itself, it depends on the scale of the project. Conversions that require excavation work will obviously take much longer, likewise if you’re having a completely new basement put in or expanding under the garden, these projects will also take a considerable amount of time longer. It is possible for smaller projects to take around four weeks but more complex basement conversions can take up to 24 weeks, potentially longer. It’s difficult to give an estimated timeframe without additional information, so it’s best to consult a specialist to get a proper idea of what the conversion entails.

How will the basement conversion affect my home?

It is possible to remain in your home and many do choose to stay put. However, bear in mind there will be a lot of disruption while works take place. Your project manager will communicate during the works and if you have issues regarding noise or mess, they’ll try and work around you. They will also try and accommodate for your neighbours needs also.

How does a basement conversion work?

Step 1: Consider the purpose

Start off by thinking about the purpose of your basement conversion. This will shape how it’s designed and the type of basement conversion you want. You can create a full retrofit basement to the house, but it helps the architect if you know what you want so they plan your needs accordingly.

For example, if you’re looking to create a downstairs cinema you won’t need to worry about lighting as a lack of light is better for the setting. If you were creating a downstairs bedroom with ensuite, you might want natural light, but you may also want to consider ventilation for the bathroom.

If you have a rough idea of what you want to use the new space for, or what features you would like adding, this is helpful to know before designing.

Step 2: Consult an expert

It’s ok having nice plans and creative ideas, but they mean nothing if the project isn’t viable. Consult an expert who will be able to analyse your building, the property and see what work is involved. They will be able to explain how realistic your ideas are and make recommendations as to the type of conversion needed.

Step 3: Seek planning permission

If your basement conversion involves external alterations and construction work, you will need to apply for planning permission via your local authorities. You will need to draw up a basement impact statement and outline your plans and considerations to them. Your basement specialists will be able to do this on your behalf or assist you and offer advice on the requirements.

If you are living in a semi-detached home or have a party wall between properties you will need to come to an agreement with the owner of the neighbouring property about the works being done, and explain how it will affect their property. Your builders should be able to help you with these negotiations and sort out a party wall agreement between both parties.

Step 4: Let construction commence

If everything is all approved and meets regulatory guidelines, it’s time for work to commence. Excavation work comes first to create the space you need, followed by waterproofing.

Step 5: Tanking

Tanking is where you waterproof the structure of the basement. This stops moisture seeping in and it’s an important part of the conversion process. Builders will often insist on a sump pump drainage system for basement conversions also – they move water away from the house to prevent flooding.

Step 6: Finishing

Once the construction work has been done and the basement has been tanked, you can then start on the fit-out process. This will involve flooring, insulation, heating, electrics, plumbing and decorating. A lot of basement conversion companies will handle the entire process to make this transition as smooth as possible.

Once you’re basement is finished, it’s yours to enjoy.