How much does a house extension cost in the United States?

ARTICLE Stephanie Matheson

Costs for same-level house extensions in the United States start from approximately $25,000*, but can easily exceed $150,000* - it all depends on the project. Adding a room or extending your living area on the ground floor are affordable ways of creating more space. Here are some key points to consider that will help you keep your renovation costs in check.

How much should I budget for on a house extension?

Ground floor extensions are typically more affordable than converting a loft or excavating basement space. Renovation costs for a same level extensions are usually between $25,000*-$75,000; depending on your materials, labour and project management. As a rough guideline, earmark around $25,000* for a one-bedroom addition to your home. Smaller renovations may work out slightly more expensive per square metre than larger renovations, as many of the overheads (such as permits) stay the same. It’s best to get a fixed price from your renovation consultant before the project starts to ensure your renovation comes in on budget. If your budget is tight, focus on the things you really need and start a list of possible ‘wants’ to add to your home further down the track.
Early estimates from your chosen building provider are usually a guideline based on a series of assumptions. Even when you get the actual quote, plan in a contingency budget of at least 20% for unforeseen problems and extras. This will help you cover expenses such as having to repair leaks or taking care of structural problems without jeopardising your renovation project.
Your builders will work from architectural plans and, to carry them out, you will likely require a minimum of a residential permit, a building permit and demolition permit - however, it’s best to speak with your local Remodeling Consulatant to find out more about any regulations specific to your state. Once the drawings for your project have been accepted, changes become very hard to implement.
Concept Drawings of a renovation are very useful. They show you what your finished renovation will look like. While they may be a little more expensive than line drawings, they help save money in the long run as the likelihood of having to change or alter your plans further down the track is reduced.

Cost of a one-bedroom extension

From $25,000

How can I create indoor-outdoor flow?

An open-plan layout with good indoor-outdoor flow is a great way of creating the perception of more space. One of the most common alterations is the creation of one large living/dining/kitchen space. Opening up walls is usually a straightforward process, however, load-bearing walls may need to be strengthened which would incur additional costs. Any electrical or plumbing points within the wall would also have an impact on the overall cost. If you are looking to simply remove a non-load-bearing wall between two rooms, you may be able to get this taken out and tidied within one day.
Sliding doors are a practical option for most room layouts and scenarios, and offer easy outdoor access from living rooms and bedrooms. They don’t open up completely, as would bi-fold or French doors, but they do allow for controlled ventilation as they can be opened fully or partially. The two standard types of sliding doors are top hung or bottom rolling systems. Top hung doors allow the bottom sill to be completely flush, however, they often require increased lintel support and installation generally takes longer, which means additional costs. Bottom rolling systems are ideal for larger, heavier glass panels.
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How can I insulate my home?

Insulation is a must these days, as it helps create a space that is less prone to condensation and easier to heat. Most heat is lost through the roof (about 42%), so that should be a top priority for your extension. About 24% of heat is lost through the walls, and 20% through the floor. If you’re using a frame construction system, insulation material should be placed within the wall framing. If your existing home is not insulated, consider if your renovation project is a good time to address this issue.
Depending on the design and style of your extension, one of the easiest and most cost-effective ways to install heating is adding an electric heat pump. It’s important to get a unit that is correctly sized for your space so that you don’t waste energy and money. Using passive solar energy can be a major money saver and help keep your home healthy and comfortable. Ask your Remodeling Consutlant at the outset of your project for options that maximise the use of direct sunlight. For example, large eaves may help let the low winter sun into your home while keeping the sun out in summer.

Do I need to install new siding during a house extension?

In most cases, when you are extending your home you will be able to keep all the original siding on your house and simply add the same style of siding to your addition so it blends in perfectly. 
The right kind of siding will keep your home weathertight and good looking for years to come. Brick or stone has long been the siding of choice in the United States. Engineered wood may be a suitable and budget-friendly alternative. 
If you do need to replace your siding, take a look at our house re-cladding case studies for pricing and options for the different materials available. 

Cost add siding

From $10 per square foot

How to save money on the interior finish when doing a house extension

Getting your new room’s walls, ceiling and flooring finished is the final step of your renovation project. If your budget is tight, focus on a basic but quality finish. You can always add custom touches and upgrade any trim and mouldings along with decorative hardware later on. When it comes to flooring, synthetic carpet or wooden laminates will be your most affordable options.
For further inspiration, check out these home extensions carried out by Refresh Renovations.

Get in touch with Refresh to discuss your house extension project

If you would like to discuss options and ideas for your house extension project, please use the enquiry form on this page to provide us with your contact details. We will get in touch with you at a time that suits you to discuss your project. If you would like to provide us with more information about your project, we have a more comprehensive enquiry form on our "Get in touch" page too.
The costs within this article are rough estimates and are subject to change. For a quote accurate to your specific project, please consult your local Remodeling Consultant.
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