House Extension 101

house extension services


For many families across Western Massachusetts, home extensions are decisions that typically come into play after a few years of living in the house as it was designed and constructed initially.

Whether the result of family additions such as children or extended family members, the desire for more living and entertainment space, or a strategic decision to increase the home's resale value, house extension projects are something we manage multiple times a month. With plenty of experience under our belt, we've been involved with home extension projects that range from small family homes where space is a concern to sprawling mansions with all the space in the world.

No matter the scope or size of your house extension project, there are a few key things to keep in mind that will help ensure its success. In this article, we'll dive into those things and also outline some of the different types of house extensions available as well as their costs. First and foremost, it's important to partner with a qualified home extension specialist or wood framing contractor who has experience managing projects like yours. Not all construction companies are created equal, and some will have more experience than others when it comes to house extensions specifically.

Once you've found the right partner, the next step is to develop a clear vision for your project. What are your goals? What needs does your family have that aren't currently being met by your home? Answering these questions will help you and your construction partner determine the best way to approach your project. From there, it's time to start getting into the nitty-gritty details. What type of house extension are you looking to build? There are a few different types available, including attic conversions, two-story additions, and even entire new wings. Depending on your space constraints, budget, and other factors, you may want to opt for one type of house extension over another.

Once you've decided on the specific type of house extension that is right for you, it's time to start thinking about costs. House extension projects can be expensive, and the cost will vary depending on the type of extension you're looking to build as well as the size and scope of the project. Attic conversions are typically the most affordable type of house extension, followed by two-story additions. If you're looking to add an entire new wing to your home, however, you can expect to pay significantly more. Overall, the key to successful house extension projects is partnering with an experienced home construction company and staying organized throughout the process. With these steps in mind, you're sure to have a home extension project that exceeds your expectations!

With the basics covered, let's dive into the costs and get a better understanding of how each type of extension affects the budget.

Depending on how much existing space you use, the room's intended function, and where you want to add on, there are several expenses connected with adding an extension to your home. In general, you'll spend roughly $200 per square foot on your extension. Complex extensions can increase the cost per square foot, while simple ones may reduce it.


Cost Breakup by Extension Size


house extension budget


200 - 300 Square Feet

The average cost of adding a 200-300 foot extension to your home can vary between $40,000 and $60,000. This figure too can vary depending on the design, materials used, and so forth, but this sized extension is more than big enough to accommodate a master bedroom, dining area, living room, kitchen, and even task-specific spaces such as a laundry room or a pantry. Other things to consider in the price include factors like plumbing and water, electricity, heating and cooling, ventilation, etc.


400 - 500 Square Feet

The good thing about considering extensions of this size is that space and permits notwithstanding, you can consider a two-story addition with the additional space divided equally between each new floor. In terms of the cost, adding an extension of this size can cost between $60,000 and $90,000. This includes everything required for the project including site leveling, foundation work, framing for walls and ceilings, plumbing and wiring for utilities like water and electricity, etc. While on the higher side in terms of price, more space opens up a whole host of possibilities that range from sub-letting for rental income to dedicated spaces for living, working, and playing.


600 - 800 Square Feet

As a frame of reference, extensions of this size are considered 'small-apartment' sized in crowded cities like New York and San Francisco! So, the price for such an extension can cost anything between $80,000 and $120,000. This kind of space is enough to accommodate two or more bedrooms, a kitchen, a living room, a bathroom, and so on. You could also use this extra space to add value to your home by including a home office, home gym, or any other functional space.


1000 Square Feet and More

Finally, you have the most expensive extension of all – one that is as big as 1,000 square feet or more! As expected, this extension will cost upwards of $150,000. These extensions are perfect for large families and can include multiple bedrooms and bathrooms, a home office, or an entertainment space like a home theater. In addition to the cost of construction, there are other expenses that you should consider when planning your extension. These include permit fees, site preparation and cleanup costs, design fees, materials and supply costs, and more.

While house extensions can be an expensive endeavor, they ultimately allow homeowners to add valuable space and functionality that they would otherwise not have access to. If you're ready to start planning your home extension project, be sure to work with an experienced contractor and stay organized throughout the process! With these tips in mind, you're sure to have a house extension that exceeds your expectations.


Cost Breakup by Extension Type


The simplest approach to calculate the actual cost of any development is to use a price per meter. However, when speaking with contractors, designers, or architects, they might also give you an indicative costing based on the type of house extension you're interested in.

Let's take a look at the different kinds below.


Rear Extension vs Side Extension

The average cost of adding a side or rear extension depends on the size, type, and quality of the materials used. For example, a single-story rear extension may cost around $80 - $100 per square foot, while one that is double-story can go as high as $150 per square foot.


Detached vs Attached Extension

A detached extension will usually cost more because it requires the excavation of an entirely new foundation. In addition, a detached extension also means that you will have to incur the costs of connecting utilities like water and electricity to the main house.

On the other hand, an attached extension is easier (and cheaper) to construct because it piggybacks on the existing foundation and utilities of the main house.

Popular House Extension Types and Costs

Now that you know how the costs are calculated, let's take a look at some of the most popular house extension types along with their average costs.

  • Single-Story Rear Extension – $80 - $100 per square foot

  • Double-Story Rear Extension – $120 - $150 per square foot

  • Side Extension (Attached) – $30 - $50 per square foot

  • Basement Extension – $60 - $100 per square foot

  • Sunroom or Conservatory – Between $15,000 and $70,000

  • Home Office Extension – Around $20,000

  • Home Gym Extension – Around $15,000

  • Home Theater Extension – Between $15,000 and $25,000

  • Attic Extension - Between $40,000 and $50,000

  • Bedroom Extension - Given how widely designed and spacious bedrooms can be, prices for extensions can range wildly between $35,000 and $100,000

  • Family Room Extension - Between $40,000 and $60,000, more so if special features and fittings are required.

  • Kitchen & Pantry Extension - Generally between $20,000 and $50,000, but as before, can vary tremendously depending on the required, design, features, and fittings.

  • Bathroom Extension - Usually the most complicated extension after the kitchen given the need for plumbing, water, power, and so forth, bathroom extensions can also range from $20,000 to $50,000 on average.


House Extension Project Stages


So now that the basic costs are covered, you would have hopefully gotten an understanding of what the tentative financial outlay is likely to be. Assuming you're still keen on having an extension built, let's look at what the various stages of a house extension project are.


1. Permits and Site Preparation

Before any construction work can begin, you'll need to apply for the appropriate permits and get your site ready. This includes leveling or compacting the ground, removing any trees that may stand in the way of the extension, laying down a foundation if needed, grading the area to allow proper drainage, and so on. The cost of this stage will depend on the size and scope of your project, as well as the condition of your site.


2. Framing

After the foundation is set, it's time to start wood framing the walls and ceiling of your new extension. This includes erecting support beams, installing joists and studs, and so on. The cost of this stage will depend on the size of your extension, as well as the type of framing materials you use.


3. Finishes

The final stage of construction is to add all the finishes to your new space. This includes installing drywall, painting, adding flooring, installing cabinets and countertops, and so on. The cost of this stage will depend on the type of finishes you select.


4. Furnishings

The last step in completing your new house extension is to add any furnishings you need. This includes buying or renting furniture, window treatments, lighting fixtures, and so on. The cost of this stage will depend on the furnishings you choose, as well as any additional installation or setup costs.

Whether you're adding a home office, entertainment room, guest suite, or any other space to your home, house extensions can be an incredibly valuable addition that allows you to make the most of your property. With the right planning and budgeting, you can create a beautiful and functional space that perfectly fits your needs.


Frequently Asked Questions


Is a permit needed for a house extension?

In most cases, yes. You will need to apply for the appropriate permit(s) before beginning any construction work on your extension. The cost of the permit(s) will depend on the scope of your project, as well as your location.

How long does it take to build a house extension?

The timeline for completing a house extension will vary depending on the size and scope of your project. Generally speaking, most extensions can be completed within 2-4 months.

What is the average cost of a house extension?

The average cost of a house extension will depend on the type and size of your project. However, most extensions fall somewhere between $15,000 and $100,000.

How can I reduce the costs of my house extension project?

There are a few different strategies you can use to reduce the costs of your house extension project. These include minimizing the size and scope of your project, using cheaper construction materials, working with a budget-friendly contractor, and more.

Are there any tax benefits associated with a house extension?

Yes, in some cases there may be. To learn more about the potential tax benefits associated with house extensions, speak to a financial advisor or tax professional.

What are some tips for maintaining and improving my house extension over time?

Some key tips for maintaining and improving your house extension over time include regularly inspecting the space for any damage or wear, using high-quality construction materials and finishes, hiring a reputable contractor for routine maintenance work, and more.

Whether you're adding a home office, entertainment room, guest suite, or any other space to your home, house extensions can be an incredibly valuable addition that allows you to make the most of your property. With the right planning and budgeting, you can create a beautiful and functional space that perfectly fits your needs.

Do I need to hire an architect for a house extension?

While you are not required to hire an architect for a house extension, it is generally recommended. An architect can help you design a space that meets your needs and budget, as well as navigate the permitting process.

What finishes should I use for my house extension?

This will depend on your personal preferences and budget. Some popular home extension finishes include wallpapering, painting, installing tile or hardwood flooring, adding custom cabinetry, and more.

Are there any tips for decorating a house extension?

Yes! One of the best ways to decorate a house extension is to keep the design simple and streamlined. Choose furniture that fits the space, add plenty of plants or other greenery, and opt for muted colors or neutral tones. You can also consider incorporating natural materials such as wood, stone, or marble into your design.

Whether you're looking to increase the value of your home or simply create more usable space, a house extension can be a great solution. With careful planning and execution, you can create a beautiful and functional new space that perfectly fits your needs.

If you have any questions about house extensions, please feel free to contact us. Our team of experts would be happy to help