An Introduction to Basement Conversions
A basement conversion is the process of converting the old space underneath your home into a new, habitable space. They are one of the biggest home renovation projects you can invest in and are therefore the most time consuming and expensive. Basements have many uses and can be a fantastic addition to your home if you are in need of more space or want to reinvent your property into a more modern space!
For many years, basement renovations have been thought of as the renovation of the super-rich and famous, but they are now becoming increasingly more common for homeowners in London. Whilst they can be costly, they have many different uses which can add a lot of value to your property. You can have your own home gym, a basement kitchen or a cinema room to entertain guests – the options are endless.
However, the basement construction process can be confusing and lengthy, with lots of different stages you need to progress through before having a fully completed basement in your home. First you need to know what type of basement you want, and whether it fits with your budget or not. Then you can progress to the design stages, before finally being able to start construction.
The Simply Construction Group has over ten years of experience of designing and building home renovation projects, with every one of our projects coming with a ten year warranty. Our team consists of industry experts who have the experience needed to complete your project to the highest standard, which has been recognised by several governing body accreditations including Trustmark and FairTrades.
This guide will talk you through all of the necessary steps you need to take to get the basement of your dreams and provide you with inspiration for your own basement project. If you want to speak to a member of the Simply Basement team, you can call us on 0800 917 7571 to arrange your site survey, where our experienced surveyors can discuss everything you need to know about your basement conversion.
Basement Design and Build Projects
At Simply Basement, we are able to oversee the entire design and build process for your basement project, reducing the organisational pressures of home renovation projects. We organise the complete design phase, including the initial site survey, architectural planning and structural designs, before going on to manage the building stages. We allocate one of our fully vetted building contractors to your project, assign a Project Manager, and oversee your build through to completion. Throughout the entire process we have our dedicated Customer Service Manager on hand to answer any of your questions and monitor your build.
Prior Considerations to a Basement Conversion
Investing in a basement conversion is a big decision, and there are some vital considerations you need to think about before you go ahead with your project.
• Why do I need a Basement Conversion?
• Your Basement Conversion Budget
• Is now the right time for a Basement Conversion?
• Types of Basement Conversion
Why do I need a Basement Conversion?
Basements provide your home with a whole new floor to be used by you and your family, being perfect for home gyms, swimming pools, cinema rooms and entertaining spaces. For many London families, living in a prime location can make it difficult to consider moving away if you outgrow your property. Investing in a basement conversion can be a better option if you don’t want to move to a new house but need extra space and want to reinvigorate your home.
What is your Basement Budget?
As with any home renovation project, you need to be realistic with your budget so that you are not disappointed by the design process or finished build. Every basement conversion is different, with different basement types, sizes and design options. If you want a basement fully fitted with a swimming pool and sauna, you will need to budget significantly more money than if you are just wanting a downstairs kitchen area. You can choose from a variety of different features in your basement, including what type of external doors and glazing options you want in your lighting well.
As with every home renovation project, it is always best to budget an additional 10% of the total project cost to cover any last-minute changes. Our surveyors will visit your home for an initial site survey and after discussing your plans for your conversion, they will be able to provide you with an accurate cost for the basement you want.
Is the Time Right for a Basement Conversion Project?
A basement conversion is a big home renovation project that causes a lot of disruption in the home. Most homeowners who are undergoing a basement conversion in their property move out for the duration of the construction stage, as the construction works are loud and invasive. More details of the construction stages are outlined later on in the guide, to give you an idea of the works that will be carried out in your home.
If you need to live in your property whilst the construction works are being carried out, there may be some ways to limit the amount of disruption to you and your family. Sometimes it is possible to only have the front room of the ground floor as part of the construction site, instead of the whole ground floor, leaving the kitchen available for use if needed. However, it is recommended that you and your family move out for the duration of the build, so if the time is not right for you all to do that, then you may need to reconsider a basement conversion.
What Types of Basement Conversion Are There?
There are four main types basement projects that you can have, which vary in cost and size. At Simply Basement, our surveyors are able to visit your home and discuss which type of basement fits your needs and budget best. The basement types are largely distinguished by the amount of space they add below your property, and so the type of basement you have will largely depend on how you want to use the new basement space. The four basement types are discussed below.
Full Basement Conversion
A full basement conversion is the biggest type of conversion you can have on your property, spanning the entire length of your home including any extensions to the original house. It adds the most amount of floor space and is the most expensive type of basement conversion you can have. If you are wanting to have a swimming pool or an equally large feature in your basement, this would be the type of conversion best suited to your project.
This type of basement conversion will typically have two lighting wells, one at the front of the property and one at the rear. This ensures there is ample light entering the new basement level floor of your home. If you would prefer to only have one lighting well, you could have a mezzanine floor. This type of basement conversion is also called a retrofit basement conversion, as it is an excavation project underneath an existing house.
Cost of a Full Basement Conversion
A full basement conversion costs around £400-600k (+ VAT), but this varies depending on the specifics of each project. You can be as luxurious as you like with your basement conversion, but this will add significant costs to your project. It is worth budgeting an additional 10% of your total project cost to cover any last-minute changes to your build too.
Half Basement Conversion
This type of conversion is smaller than the full basement, as it only sits under the original house, excluding any extensions to the rear or front of the property. This type of basement is good for adding a new living space to your home, such as a kitchen and living area, a gym and bathroom or some new bedrooms. It can still add a considerable amount of space to your property, despite being smaller than a full basement conversion.
A half basement can have a lighting well at the front, rear or both front and rear of the property. If you have a broken-plan layout then it can be better to have two lighting wells to ensure each room gets some natural sunlight. If you have one open-plan room, then one lighting well can be enough to allow in ample natural light. This basement type is also considered a retrofit basement conversion as it excavates the ground beneath the existing property requiring underpinning.
Cost of a Half Basement Conversion
A half basement conversion begins at £150k (+ VAT), but this can change depending on the features you have built into your basement and variables like the number of rooms you want. Again, it is worth budgeting 10% of the total project cost to cover any last-minute changes to your basement conversion.
Garden Basement
A garden basement is separate to the main house, being built under the topsoil of the garden area. These can be great for storage or for a separate living area. A garden basement tends to cause less disruption during construction, as the main house is untouched and therefore you can continue to live there during construction. This type of basement is good for smaller living spaces or cinema rooms, and due to its positioning in the garden it can get much more natural light with walk-on glazing in the garden. The garden basement connects to the main house through a new external covered staircase.
Cost of a Garden Basement
A garden basement starts at around £150k – £200k (+ VAT) but has the most variability due to the size of the garden and what you want to use it for.
Coal Cellar Conversion
The final type of basement conversion is a coal cellar conversion, which creates a small room underneath the original house, which is typically used for storage of wine or similar items. A lighting well is not built for this type of conversion, as they store items which need to be kept out of direct sunlight. They are not primarily for living in, so they do not need lots of natural lighting either.
Cost of a Coal Cellar
The price of a coal cellar starts at approximately £50k (+ VAT) depending on the size of the cellar, and if it is a new excavation or a refurbishment project which includes waterproofing it.
Design Options for Basement Conversions
There are many different design options for a basement conversion which you will need to work through and decide upon. Before construction of the project can begin, and before your project is handed over to an architect, it is good to know exactly how you want your basement to look and function.
Lighting Well
You can have a lighting well at various place in your basement which you will need to decide on, as well as how many lighting wells you want. You can have a lighting well at the front of your house, down the side, or at the rear. This will depend on what type of property you have and whether you are end-terraced or mid-terraced.
Mezzanine Balconies
A mezzanine is a floor which does not extend to the width or length of the property, creating a platform between two floors that allows you to see from one floor down to the next. These are a great design feature when paired with a basement, with the mezzanine being made from the pre-existing ground floor level, looking down into the basement.
You can be creative when creating a mezzanine, having your guests step inside your home and immediately being able to see below them. You can have walk-on glazing if you want to add a thrilling feature to your home, or you can have dramatic up-lighting to emphasis the mezzanine from the basement.
Walk-On Glazing
Another stylish way of designing your basement ceiling, is to install walk-on glazing that allows you to look through from your ground floor to your basement floor. You can line your glazing with creative lighting options to create a stand-out feature that draws your attention down into your new basement space. This is a popular design feature which can transform your basement into an incredible feature of your home.
Glass Walls
If you have a lighting well at the rear or side of your property, you can choose to have a sheet of glass that replaces the wall connected to the basement and ground floor. It creates a dramatic effect by being able to see inside both floors at the same time from the outside of your property. If you prefer your privacy, it may not be the right option for you, but if you want to dramatically light up your property at night and create a stunning view of your property, it is a feature your guests will never forget.
Courtyard
Having a basement courtyard is a popular feature currently, as it allows your garden to have two different levels. You can have a paved courtyard outside the basement level, which can be connected to the higher part of your garden with different types of staircases. Or you can join your basement courtyard up to your ground floor level with a spiral staircase.
A courtyard is a great addition for bigger properties, as it introduces a separate segment of your garden. You can dine outside and have barbeques in the summer from your basement courtyard, and you can even design a bridge from your ground floor to the higher garden level too!
Basement Conversions – The Process
Site Survey
The basement conversion process starts when you give Simply Basement a call on 0800 917 7571 to arrange your free, no obligation site survey by one of our surveyors. Our surveyor will visit your home and discuss your thoughts and ideas for your basement. They will discuss your budget with you and the type of basement conversion you are thinking of having, and whether it is feasible within the budget stated. The surveyor will then take appropriate measurements ready for them to start drafting up the first set of plans for your basement project.
The first set of plans will outline the costs of each part of your basement design and the floorplan for your new space. You will be given a quote outlining everything that is included within the total price, and some options you have to choose from (like sliding or bi-folding doors). In some cases, you will provide some of the materials for your building team like the doors you choose. If you are happy with the quote and the contract, you will sign the contract and we will commence the design process for your basement conversion.
Basement Design Process
After your surveyor has visited your property, your property will then need to undergo different tests. The water table level will be looked at, drainage considered, type of the soil will be measured with a Geo-Technical Survey. Sometimes, a high-tech piece of equipment will be used to track where the drains are underneath your house, to ensure that they can be redirected or avoided during the excavation process. You may also need an Arboriculture Survey to investigate the tree roots stemming from you and your neighbours’ gardens, to ensure they are not at risk from the basement project. If you live in London, your architect will even need to consider the London Underground tunnels!
Your architect will work within a team of professionals, including your surveyor, a structural engineer and a waterproofing specialist. It is essential to have a waterproofing specialist involved in the design stages of your basement conversion project, as they will be responsible for making sure your basement is water-tight and for understanding the different soil qualities. Once your team have finalised their plans for the basement and you have approved them, they can then apply for planning permission from the local council.
Once approved, your structural designer will take the lead on your plans to transform the intricate architectural plans into a set of stages for a building team to follow. Their plans will describe the sequencing of the construction process, steelwork and under-pinning details, and party wall detailing. It is only once these structural plans have been approved that you can start obtaining a Party Wall Agreement with your neighbours.
Basement Build Process
There are two main stages within the construction phase of your basement project. The first is creating the basement ‘shell and core’, which is the solid structure beneath the ground including all waterproofing and excavation. The second stage is the fit-out, where the interior is fitted out to a plastered finish including any electrical wiring and plumbing.
Typically, the construction process takes around five months to excavate, under-pin and complete tanking (waterproofing). The excavation process is typically the most disruptive, as the soil is removed by a digger putting the waste onto a conveyor belt which comes up into the ground floor (normally into the front room) and out of a front window to a skip. This can completely take-up the ground floor of your home and the machinery is loud and muddy! It is therefore recommended that you move out for the duration of the construction phase, especially the first couple of months of excavation.
The tanking process ensures that any moisture from the concrete foundations of your basement, does not leak through to the interior. It diverts the moisture to what is known as a perimeter gully which is directed to a sump-pump that removes the water. Once this stage has been completed, your basement will be ‘actively tanked’ and waterproof.
The fit-out process will then start and can take up to three months to complete, sometimes longer for larger projects. In total, your basement project can take around a year to fully design and build, assuming the planning permission process is without any setbacks and your Party Wall Agreement is quickly sorted.
Basement Planning Permission
Within the construction industry, there are two types of planning permit that you could need for your basement project. The first is called permitted development, which are a set of restrictions that if you follow mean you do not need to apply for planning permission. Planning permission is the second type, which is where you have to seek approval from your local building authority for your project as it falls outside of permitted development.
For basements, in the simplest form, you will need planning permission for any large-scale basement project that includes a lighting well or any change to the exterior of the property. Your project will only fall within permitted development if you do not have a lighting well and are renovating or creating a smaller space like a cellar.
Currently, the planning regulations for basements are being reviewed, but you can contact your local planning authority to find out more on the specifics for your area. Here are a couple of London boroughs who have different regulations on basement builds:
– Royal Borough of Kensington & Chelsea: you can only have a basement of one storey, which does not extend more than half of your garden.
– Wandsworth: You need to keep a depth of 50% of your garden.
– Merton: You cannot extend further than 50% of your garden to the front, rear or side of your property.
If you live in a conservation area, it may not be possible to have a basement conversion due to the restrictions to protect the natural environment. You can find out if you live within a conservation area online, or by speaking to your local planning authority.
Basement Conversion Party Wall Agreements
For a basement conversion project, you will need a Party Wall Agreement between you and your neighbours. This agreement covers the work your neighbours are willing to allow you to have on any shared walls or boundaries of their property. They are required by law, and you will typically need a Party Wall Surveyor to oversee your agreements for a basement project.
You will need to serve a Party Wall Notice if the party wall will be affected by the work you want to have done on the property. As your basement project will include an excavation process any properties within 3-6 metres of yours will need to be notified. Your neighbours have 14 days to respond to your Party Wall Notice before it will be taken to dispute. This can be costly and timely, so it is important you get this sorted well before construction is due to begin. Once you have approved your Party Wall Agreement you have up to a year to begin construction work on your property, but due to the length of the basement design process, it is recommended you begin this process once you have confirmed the architectural plans.
Our experienced and qualified surveyors will be able to guide you through the paperwork needed for a Party Wall Agreement, and our team are on hand should any dispute arise. It is important to note that you will need your neighbour’s approval in writing. Should your plans change, you normally do not need to serve a new notice, you will only need to show your neighbours your revised plans. Our team at Simply Extend have years of experience negotiating party wall agreements and can help to make the process as simple as it can be.
The Simply Basement Service
Simply Basement takes pride in the quality of our fully bespoke basement conversions with experienced professionals being involved in every stage of your build. You are treated with the highest respect from the moment you contact us, with our surveyors and professionals working to your schedule to make your project a reality. From your meeting with one of our qualified surveyors, through to ten years after your project has been completed, you will have access to our dedicated Customer Support Manager. We prioritise you and your family and will always work to keep you happy and comfortable.
All of your important documents and communications are kept together on our Simply Dashboard, so you do not have to organise or worry about losing any information. Your designs, paperwork and conversations with any member of our team are documented on this site, which you can access at any point in time. For a basement project, this is incredibly useful as it can take many months and lots of paperwork before construction begins. If you have any issues arise in your build process, our Customer Service Manager will listen to you and sort out any problems you have swiftly and efficiently.
We offer complete transparency with our prices, offering a fixed fee promise. We will give you an accurate and fully-costed quote for your basement build, which will be confirmed in the final stage of the design process. Unlike many other home renovation projects, there are fewer opportunities to make last-minute changes, so you will not have to worry about raising costs as your build goes on. Our surveyors work closely with our architect team, to make sure their initial quote is as close to the final quotation as possible – a service not offered at other construction firms.
Our knowledge of the industry and connections makes us stand out from the rest, with accurate prices and no nasty surprises. As with every building project, we recommend you budget up to 10% extra on top of your build to cover any changes that are made, and your surveyor can work with you to make that affordable. Our building teams will do everything they can to make sure you are kept up-to-date with the progress of your build, so you know exactly what is happening and when.
All of our projects come with a ten-year warranty, so that you feel covered and cared for even after construction has finished. We are proud of the accreditations we hold from TrustMark, FairTrades and the Guild of Master Craftsmen which show we have been heavily vetted by the best in the industry.
Simply Basement are ready to start working on creating your perfect basement extension, whether you want a home cinema, personal gym or even a personal bar! Call us today on 0800 917 7571 to arrange your free site survey with one of our qualified surveyors, and start making a dream into a reality.
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