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Extend a House | What to Consider

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More people are seeking advice to extend a house. Many homeowners decide to improve their space rather than find a new house to call ‘home’. But what should you consider before extending your property? From knowing how to get planning permission to the design process, here’s everything you need to know about extending a house.

Is it a good idea to extend your house?

Extending your house can create more space and add value to your property. Whether you need more room for a growing family, a home office or simply want a bit more space for a comfortable living environment, an extension may very well provide a solution tailored to your needs.

One of the main benefits of extending your house is that it can be more cost-effective than moving to a larger property. Selling your home, finding a new one and moving can be stressful, time-consuming and expensive. You may be able to avoid many of these issues and create the perfect home that meets your needs by extending your current property instead.

A home extension can also add value. A well-designed and built extension may increase the overall size and functionality, making it more attractive to potential buyers if you decide to sell in the future. Not only that, but you can create a more modern and desirable living space, which can be particularly appealing to buyers looking for a home that requires little work.

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What to consider before you extend your house

Extend your house to add value

If done well, a house extension can add value to your property while increasing the living space. How much it increases the value of your home depends on several factors, such as the location, size and quality of the extension, as well as the current state of the property market. Some estimates suggest that a well-designed and built extension can add around 20% to the value of your property.

Permitted development and planning permission

  • Permitted development. Permitted development rights allow you to carry out certain types of building work without the need for planning permission. These rights vary depending on the size and location of your property, as well as the type of work you want to carry out. It’s important to note that there are limits and conditions to what you can do under permitted development, so it’s always a good idea to check with your local council before starting any work.
  • Planning permission. Planning permission is a formal process needed to go through if your proposed building work falls outside the scope of permitted development rights. You’ll need to submit a planning application to your local council, which assesses the plans against various criteria, such as the impact on the local area and whether the design is in keeping with the local character. The planning process can last several months and may be expensive, so you should factor this into your project plan and budget.

Building regulations

Most house extensions require building regulations approval. These regulations set minimum standards to ensure the safety of building occupants and the public. Approval must be obtained from the local council’s building control department through a full plans application or a building notice. Ensuring compliance is necessary to avoid safety hazards and enforcement action.

Your home insurance cover

Before starting an extension project, review your home insurance policy to ensure you have adequate coverage during the building work. Notify the insurer and check policy limits to see if there’s sufficient coverage for the extension and any new contents. You may also want to consider specialist cover, such as structural defects or site insurance.


If you own a leasehold property, you’ll need to check whether permission is required from the freeholder or management company before doing any building work. This may involve obtaining a licence to alter or make changes to the terms of your lease. It’s also good to consider how the extension may impact shared areas or services, such as access to the property or parking facilities.

Your neighbours

Inform your neighbours of your plans so they are aware of any potential disruption or inconvenience that may be caused during the building work. It’s worth discussing plans with your neighbours and addressing potential concerns they may have. If your proposed building work affects your neighbour’s property or right to light, you may need to obtain their consent or apply for a party wall agreement.

Party Wall Agreement

A party wall agreement is a legal document outlining the rights and responsibilities of both you and your neighbour during the building work. You’ll need to notify them of your proposed building work, and they will have the right to appoint a surveyor to represent their interests. The surveyor assesses the potential impact of the building work and draws up a party wall agreement setting out the terms of the work.

Designing an extension

Finding an architect

Choosing the right architect is one of the most important factors when extending your house. Look for an experienced and qualified architect with a portfolio of previous work that aligns with your vision. Check their references and testimonials from previous clients, and choose someone who communicates the design process well and listens to your needs.

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How to brief an architect

To brief an architect for your extension project, start by clarifying your requirements and objectives. Provide a clear description of the space you want to create and the problems you want to solve (eg, is it an additional bedroom, office space or kitchen?). Be clear about your budget and timescale and provide relevant drawings, photographs or plans if possible.

Obtaining structural engineer calculations

Obtaining structural engineer calculations make sure the building work is safe and structurally sound. The structural engineer will assess the load-bearing capacity of the existing structure and design any necessary reinforcements while also designing the foundations and ensuring that the building work complies with building regulations.

Choosing a builder

How to find trusted professionals

When looking for trusted tradespeople, seek recommendations from friends, family or online reviews. Check credentials, qualifications, insurance and any accreditations they may have. You should also obtain quotes from multiple tradespeople (more on that shortly) and ask for references. A trusted tradesperson can help ensure the success and safety of your project.

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Home extension costs

Home extension costs vary depending on factors like size, location and design complexity. Other costs may include planning and building regulation fees, as well as any professional services such as architects and structural engineers.

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Getting quotes

Obtain multiple quotes from trusted tradespeople and ensure they provide detailed breakdowns of costs, including materials and labour. Be clear about your requirements and any constraints, and don’t be afraid to ask for references from previous clients. Comparing quotes can help you to make an informed decision and stay within budget.

Setting a budget

Be realistic about your budget and factor in any unexpected costs. Allow for a contingency fund to cover unforeseen expenses- it’s not uncommon for building work to go over budget. Careful budgeting can help you to plan and execute a successful and stress-free extension project.

Extend your house the right way

Undertaking any home extension isn’t a quick decision, and there’s plenty that goes into the process. It takes time and can be hugely rewarding when done right. Take the right steps, and you can enjoy a larger space and a whole new dynamic to your home.

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Last Updated: August 22nd, 2023

Phil Spencer

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