BASEMENT CONVERSIONS IN LONDON

Understanding the Basement Conversion Process

1. FREE SITE VISIT

One of our construction specialists comes to meet you in person and view the site. We cover all areas in London.

• Meeting in person: understand what you want and the challenges within

• Seeing the place: place the vision in the physical constraints of your house

• Understanding the context: collect details and impressions and explore the neighbourhood

• Discussing your ideas: identify challenges, prevent issues, remove blockers

When creating or converting a basement under an existing building, and even creating a basement for a new build, it is important to understand the physical constraints. A lot of info can be gained from the council planning authority, but a site visit always reveals more than any document can do.

Many elements can affect the feasibility of a basement, including party walls, layout, nature of the soil, underground structures like road tunnels or tube tunnels. Also, a visit to the neighbourhood will give us an idea of whether there are similar developments in the area, which would mean it’s more likely to get planning permission. If you are converting an existing cellar, for example, it is possible your basement conversion will fall under permitted development work and you won’t need to apply for planning permission.

2. THE PRELIMINARY PROCESS

In preparation for a basement project, you will need to take care of the formal procedures. They might include planning permission, building regulation, method statement, party wall agreements and so on. Our architects have experience in all councils in London

• Understanding the context: evaluate all the physical factors that affect the conversion of a basement. Things to take into account are the load of the building above, the nature of the soil, the water table level, the underlying existing structures like services, tunnels, tube etc

• Determining the formal process: understand the legal aspects and studying the council regulation; investigate the layout of the neighbourhood and the adjacent properties; define the need for party wall agreements, external technical reports, method statement etc.

• Making the right decisions: maximise the value created by adding the basement, against the budget investment, when all the feasibility constraints are clear, choosing the best options for structure, design, usage, dimensions, layout etc.

• Finalising the pre-construction phase: producing all the documentation including plans, technical drawings, structural calculations, method statement, work plan, submitting the plans to the council for permitted development or planning permission, serving the party wall notices and completing the party wall agreement

When converting a basement, the most important factor is to optimise the budget investment and maximise the generated value from your property. To achieve that, technical competence and experience are crucial to evaluate your options and make the right decisions.

Technical complexity, the neighbourhood, the length of the pre-construction process, the cost of external consultants and many more technical elements will support you for the best planning of your basement conversion.

3. FREE CONSTRUCTION ESTIMATION

One of our estimation specialists produces an accurate quotation, including a breakdown of all the details and their cost

• Defining the costs: evaluate the basic construction work

• Estimating the options: optimise the choice of finishes and suppliers for the best result

• Explaining the quote: communicate clearly what is included or not and what might be the impact

• Communicating effectively: explain the process and the program, define the communication channels, agree on the decision flow

Investing your money in renovating your property can be a big decision. That is why understanding the quotation is paramount to make the best decision. Most important of all, the price must be reasonable. Rogue companies often quote a very low price to get appointed, already planning to charge extras to make up for the difference; if not done on purpose, a contractor might choose to abandon the project when they realise it’s not profitable.

4. BUILD

Basements need special attention to the construction procedure, because of the higher risk related to the existing buildings during the work.

• Enforcing the method statement: create instructions for the team to carry out the work. Those include accurate descriptions and precise details, like props for vertical and lateral support, temporary roof, usage of conveyor belts for soil removal etc

• Appointing the teams: choose experienced and well-tested basement specialists to carry out the work and the best project manager

• Supervising the site: stay involved with day-to-day activities on-site, to provide guidance and coordinate the personnel, the supplies and the procedures on-site

• Reporting and sharing info: give regular feedback and respond promptly to questions and requests

• Setting up communication channels: dashboard, live chat, photo and video sharing using the latest tech solutions

• Making timely decisions: follow a clear process for requests, approvals, last-minute changes and all decisions

Building a basement requires technical competence and experience and basement contractors work better under the supervision of professional experts. On top of that, information sharing and effective communication are also important to ensure the best results.

That is why with Home Constructive you will have a structural engineer in charge of your basement conversion, plus dedicated communication channels to ensure the decisions are made promptly and the crucial information is always at hand.

5. FIT-OUT, COMPLETION AND HANDOVER

Your construction project manager ensures you make the best decisions for your fit-out and finishes and the best tradespeople are appointed to deliver the best results for your basement

• Finalising the approval of the finishes: although the requirements on the finishes are often defined in the design phase, it is important all the details are approved by you. Windows, flooring, lighting, doors, paint, tiles, fittings are all details that make a difference in the quality of a basement

• Appointing the best teams: choose the right tradespeople for all the work on-site; electrical and plumbing, for example, are crucial to a successful project and the wrong choice can cause a lot of problems in the future. Home Constructive ensures you get the best specialists for electrics, plumbing, tiling, painting, flooring, decoration etc

• Wrapping up all the final bits: make sure all the little details that need to be retouched are taken care of beforehand over

While building the shell of your basement is very important, you want to make sure that the space you create is pleasant to be used and lived in. In that, the finishes are essential, and we will make sure you are involved and informed so that you can choose the best for your requirements and have everything executed at top-notch quality.

Tanking and Waterproofing

Tanking is a building technique for underground structures that control the water that comes from the external soil, using draining channels to remove the excess of water, while the basement is protected from infiltrations by a tank that surrounds the walls and the base of the basement. For the tank, cavity drain membranes, channel drains and sump pumps are employed. The pumps are installed with redundancy and alarms. So secondary pumps can take over when the primary is full or not operating properly, while the alarms signal issues in the correct functioning, like battery exhaustion.

Waterproofing is a more generic term for ensuring that a structure, underground or overground, is not infiltrated by water, causing damp. In the case of the basement, waterproofing membranes are added to the tanking, to prevent water penetrating the basement.

At Home Constructive we have the in-house expertise to design and implement the latest technologies and the most effective waterproofing systems, to ensure that your basement is built to last longer.

Planning and Permitted Development Requirements

For basements in London, permitted development is restricted to not substantial alterations. You can convert an existing cellar or basement into a living space within permitted development rights.

Any excavation for a basement requires planning permission. Approval rate for basement conversions planning applications is very high, because councils usually grant permission. The process for the application, though, is a bit more complex, due to the amount of required documentation, reposts, investigations and other conditions that are specific to basement applications.

The final result is very predictable, but the process to get there is usually longer and has higher cost than applications for standard extensions like loft conversions or rear extensions.

Basement Conversion Budget

A basement in London is relatively more expensive compared to other types of extension alterations, so it is important to understand the costs and the value generated. The value will depend on the existing property, the area of London it is located, the size and the quality.

Variables that affect the cost can be:

• Structural design: an efficient structural design can save on materials and costs, with the same final result

• Construction process: following the correct procedure and building in the right time of the year can avoid contingency costs

• Soil constraints: the nature of the soil can require specific measures, like piling foundations or thicker retaining walls and slab

• Party wall agreements: depending on the number of adjoining properties and involved parties, party wall agreement can add up to the costs

• Design choices: using materials like structural glass, expensive internal finishes and other specifications can change significantly the final cost

AVERAGE COST

It can help to have an idea of how much your basement conversion costs as an average. It’s important to always keep in mind that many variables can add to the average cost; other conditions can make the cost lower. Make sure you work with the right company that can support you make the choices that are best for you, also considering your budget requirements.

Baseline costs of construction in London, which don’t include professional fees and finishes like flooring, windows, doors, furnishing and joinery, fittings etc:

• Creation of a new basement under an existing building: £2,500 to £3,500 per sqm

• Conversion of an existing cellar: £1,750 to £2,750 per sqm

• Extension of an existing basement/cellar to the garden: £2,000 to £3,000 per sqm

Why Choose Home Constructive

Once you have decided exactly what you want with your extension, you can begin your journey to a bigger and better home with Home Constructive. Throughout the process, Home Constructive will provide you with a dedicated, knowledgeable project manager that will answer any questions you might have during the build and ensure that you are 100% happy before, during and after the transformation. So, if you’re a homeowner in London looking to expand and improve your current living quarters, rest assured that Home Constructive will turn your visions and paper designs into a reality.