The Ultimate House Extension Guide

A house extension is often the most cost-effective way of creating more space in your home or remodelling it to suit the way you want to live. From simple kitchen extensions and sunrooms to large and complex extensions with internal alterations, you can gain a unique home that’s perfectly suited to your needs.

Every building is different. The type of house extension, as well as the final design and layout, will depend on your individual requirements and preferences. Working with the right architectural design professionals can help you find innovative solutions to create more usable space. Before you make any decisions, you should make sure you’re fully informed about your options and the design process for your house extension.

Why extend?

There are several reasons why people decide to extend their home.

Need for additional space: One primary reason for house extensions is to create more living space. Growing families, the need for extra bedrooms, a home office, or additional storage are all common factors that drive people to extend their homes.

Changing needs and lifestyle: As people’s lifestyles evolve, their housing requirements can change. They might desire a larger kitchen, a spacious living area for entertaining guests, a dedicated playroom for children, or a home gym. Extensions allow homeowners to tailor their home to meet their specific needs.

Avoiding the cost and hassle of moving: Selling a home and buying a new one can be a stressful and lengthy process. It can sometimes be more cost-effective and convenient to invest in an extension to an existing property instead.

Increasing property value: A well-designed and professionally executed house extension has the potential to increase the value of a property. This can be advantageous for homeowners who plan to sell in the future. They can potentially recoup the cost of the extension and make a profit.

Enhancing aesthetics and curb appeal: Extensions can transform the appearance of a house, making it more visually appealing and modern. By adding architectural features or expanding the living space, homeowners can improve the overall look and curb appeal of their property.

Adapting to circumstances: Some homeowners may require modifications to accommodate specific circumstances. For instance, people with mobility issues might need to incorporate accessibility features like ramps, wider doorways, or a downstairs bedroom and bathroom. Alternatively, individuals who work from home could opt for a dedicated office space to create a productive and separate work environment.

Maximising the potential of underutilised space: Some homes have areas that are currently underutilised, such as lofts, basements, or garages. By converting these into functional living areas, homeowners can make the most of their property’s square footage.

Where to start

When contemplating a house extension, it’s essential that you don’t fixate on a specific goal. Instead, you should be prepared to explore various options and ideas. Carefully consider your current and future needs, allowing for flexibility and adaptability. Engaging in this broader perspective opens the door to creative solutions that you may not have initially considered.

Whilst looking at what a neighbour has done can be helpful, engaging professional architectural services can be invaluable. As architects, we can assess your home’s existing layout, then offer insights into design possibilities. We can ensure that the extension harmonises with the overall aesthetic and functionality of the property. Our expertise will help you envisage the additional value an extension can bring. We’ll be able to walk you through the whole extension project with ease and clarity.

Types of house extensions

There are many ways an existing house can be extended. The most popular are single storey rear extensions, two storey side extensions and sunrooms. Each house is unique and comes with its own limitations and advantages. Keep an open mind and an experienced architect will advise on the best solution for your individual property.

Single storey rear/side extensions are the most common type of house extension as they are so versatile and can add additional living space without too much disruption. They may create a larger kitchen, add a dining room, extend the living area, build a home office or study, incorporate a playroom or family room, or even construct a new bedroom with an ensuite bathroom. The design and layout of a single storey extension depends on the specific requirements and preferences of the homeowner. A few things to consider are the proximity to the neighbouring properties, especially if you live in a semi-detached or terrace house, the impact of the garden space and if there are any restrictions on the land (e.g. greenbelt, open countryside or an existing covenant).

A two-storey extension can significantly increase the living space of a property by providing additional rooms like bedrooms and bathrooms, as well as a larger downstairs living area. This type of house extension is often to accommodate a growing family’s needs or to create extra space for specific purposes, such as a home office, gym, or hobby room. The same considerations for a single storey extension apply and the overall impact on the street scene needs to be considered.

Sunrooms and orangeries have become increasingly popular with people wanting to add an additional room or replace an existing conservatory. Most people find their conservatory has limitations as they can be too cold in winter and too hot in the summer. With the increased cost of heating a home, it has become more important than ever to make these spaces cost effective and usable. One option is to change the roof of the conservatory, but this will only help a little and is not as cost effective as a purpose-built sunroom. A well-designed sunroom can provide all the benefits of a conservatory, with natural light, large windows and access to the garden whilst meeting the current Building Regulations for energy efficiency.

Building over an existing attached garage can be a great way to utilise unused space without increasing the footprint of a house. Many garages are built with single skin brickwork, so additional structure is needed to support the new structure above. The existing foundations also need to be checked to see if they are suitable to carry the additional load. Building over a garage can often enable the homeowner to add an additional bedroom with ensuite and dressing room.

A porch may feel like a small building project but it can have many benefits. It will add curb appeal, provide additional space and act as a weather buffer for the rest of the house. Another appealing aspect is that porches less than 3m/sq do not require planning permission. You will still need building control approval, but we can design a porch that is in keeping with the rest of the house and produce the technical drawings required for building control.

Converting a loft can offer several benefits and is a popular choice for many clients. One of the main reasons for converting a loft is to create additional living space within your home. It allows you to make the most of the available space in your property without the need for an extension. Often the space in a loft is under utilised, often used as storage, so converting the loft allows you to transform this wasted space into a functional and valuable part of your home.  By adding this usable square footage, you are effectively increasing the overall living space, and as a result increasing the value of the property.

 A Garage conversion is another great way to make use of the existing footprint of your house and is a really easy and practical way to create another room on the ground floor. Most garage conversions don’t need planning permission, but they will need to be signed off by building control.

Stage 01 – Preparation and Brief

During this stage, we meet with the client to understand their requirements, analyse the site, and discuss their vision for the single storey extension. We will prepare a comprehensive brief based on our discussions and conduct any necessary initial surveys. This process enables us to understand how the client envisages the end result, what elements of the design are most important to them and if there are any limitations due to the site or location.

Stage 02 – Concept Design

Based on the brief from the client and our site analysis, we will develop concept designs that explore various options for the single storey extension. These designs illustrate the spatial layout, form, and overall aesthetic of the proposed extension. Where it is applicable we may produce more than one design solution for discussion. At this stage we can provide initial cost estimates in conjunction with a Quantity Surveyor. We will also review any planning constraints or building regulations that may have an impact on the final design.

Stage 03 – Design Development and Planning

Most house extensions require planning permission from your local authority. Although small single storey extensions often fall within ‘Permitted Development’ and can be built without planning permission. DMA recommends obtaining a Certificate of Lawfulness to ensure the extension meets the strict Permitted Development rights. For the planning application DMA will refine the drawings, complete all the application forms, prepare the site and location plans and submit the planning application via the planning portal. DMA will also handle all communication with the planning department regarding the application and make any necessary adjustments following feedback from the planning department.

Stage 04 – Technical Design

It is a legal requirement to obtain Building Control approval for almost all building work. DMA has the knowledge and expertise to produce a full set of technical drawings that comply with the current building regulations. We work with the structural engineer and other consultants to ensure all the information is available and coordinated for the building control ‘plan check’. DMA will submit the drawings to building control and make any necessary changes. Once the drawings have approval we issue a full set of Technical Drawings to the client to ensure the builder has all the information before they start work on site. Building control must be notified 5 days prior to any work starting on site by either the builder or the client. The fee for building control varies depending on the size of the extension.

Schedule of Works

For larger or more complex projects a Schedule of Works can be produced to accompany the Technical Drawings giving more detail of the materials, finishes and fittings in each room. This can be beneficial when you want to have a more accurate price from the builder and can remove the added stress on site due to unforeseen costs. However, many clients building single storey extensions can work through these details with their builder prior to work starting.

Tendering Process

The success of your project will be linked to the builder you choose to construct it and how your agreement is set up. We advise that you seek competitive tenders/quotes from suitable companies and we can manage that process for you, sending out the paperwork and checking tenders for you. We can also recommend builders we have worked with successfully in the past. It is also worth checking if your builder is a member of a suitable organisation such as Federation of Master Builders.

Stage 05 – Contract Admin and Site Inspections

Many projects have no formal agreement or contract in place before work starts, making disputes difficult to manage and resolve. We can assist you in choosing the right form of contract for your single storey extension. The contract between the client and the builder, sets out when they get paid and how much, how you deal with changes, what happens if the project overruns and how defects are dealt with. We offer a Contract Administration and site inspection service where we will prepare all the contracts, inspect the works on site on your behalf, checking for conformity with the contract drawings and that workmanship is to a suitable standard. We also liaise with the builder to make sure you receive the suitable certificates and paperwork at the end of the project.

Budget, Costing & Fees

Budgeting for your building project is important and the cost for a single storey extension can vary greatly. The area you live in, the materials chosen, and the size and complexity of the project will all have an impact.

We try to ensure you are aware of all the architectural services fees and associated costs from the beginning. Typically, these are approx.10% of the construction cost, but can vary from project to project. We recommend using the Love Renovate cost estimator to get an initial price based on the size of your extension.

Once concept design drawings have been completed we can arrange for a cost estimate. To get a full cost breakdown you can appoint a Quantity Surveyor to price the Technical Drawings prior to appointing a builder. Alternatively, most builders will give you a price for the works prior to appointing them.

Unforeseen costs can be one of the biggest stressors on a building project, so it is worth having a contingency fund. We recommend adding 5% to the contract value to cover these.

Keeping costs down

The areas where we often see costs rise are where high-end sliding doors and rooflights are specified. We all like the minimal lines of some of the high-end door manufacturers, but these types of doors can cost two or three times other options. Expensive kitchens are another budget buster, with some companies charging large mark ups for fairly run of the mill kitchens. Don’t discount using Ikea or Howdens and finishing it all with nice bespoke worktops. Flooring is another area that can mount up so shop around and make sure you have looked at quality as well as price. We can use our experience to guide you through options.

The areas where we often see costs rise are where high-end sliding doors and rooflights are specified. We all like the minimal lines of some of the high-end door manufacturers, but these types of doors can cost two or three times other options. Expensive kitchens are another budget buster, with some companies charging large mark ups for fairly run of the mill kitchens. Don’t discount using Ikea or Howdens and finishing it all with nice bespoke worktops. Flooring is another area that can mount up so shop around and make sure you have looked at quality as well as price. We can use our experience to guide you through options.

Process & Timeline

• Stage 1

  Preparation and Brief

  Day 1. First meeting with the architect, who will carry out a survey of the site

• Stage 2

  Concept Design

  Approx 4-6 weeks from initial meeting and survey

• Stage 3

  Design, Development and Planning

  Planning can take 2-6 months depending on the local authority

• Stage 4

  Technical Design

  Approx. 10-12 weeks to complete the drawings and coordinate with other consultants

• Stage 5

  Construction

  Varies greatly but a simple single storey extension will typically take 12-14 weeks to build

Snagging & Warranties

At the end of the project it is always a good idea to walk the project with the builder and note any points of snagging that need to be rectified before they leave. This could be as simple as a mis-aligned socket to a damaged door or window. Many issues will have been resolved on site during the build. If you have a contract in place then you will have an agreed period of time for the builder to rectify any snags. It is also good practice to get any warranties from the builder for windows, doors, new boilers, etc. DMA can assist with the sanggin process should we be required.

Paperwork

Both your planning approval and building control approval are legal documents and should be kept safe. Also all certificates from the builder need to be kept and some need to be shown to building control for the final certificate to be released. For example; commissioning certificates for a new gas boiler, electrical safety certificates, mechanical extract fan test results, fire alarm test and installation certificates if they have been upgraded.

Building Insurance

As the homeowner, it is your responsibility to inform your insurance company that work is taking place. They will want to know if you are going to remain living in your home during construction or if the house will be vacant. They will also need a rough idea of how long the work will take. It is worth contacting them again at the end of the construction phase to tell them the work is complete.