How much will a home extension cost me? | homify

How much will a home extension cost me?

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The Cube, Winchester Modern houses by Adam Knibb Architects Modern
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We all know that we love our family home, and don't really want to move away. Yet, at some point, we realize our home is too small, perhaps because we've had children, or our children have grown. Or, maybe your rooms aren't enough anymore, as you need an office or space for a new hobby. In all of these cases, extending the home is a good alternative to moving. But, what does an extension cost? We have put together a guide to help you plan it out. 

1. The simple extension on the main floor

Ground Floor Extension, Drury Rd Classic style houses by London Building Renovation Classic
London Building Renovation

Ground Floor Extension, Drury Rd

London Building Renovation

A house extension costs, per square foot, anywhere from 80 to 200 dollars. A lot depends on where you want the extension and what's involved. While determining prices in the country is simple, and often cheaper, cities can be harder to plan for, with red tape you'll need to maneuver around. It's also worth noting that it's more expensive to add to an existing house that is high-end-- as the extension needs to flow with the rest of the home. 

2. Second-story extension

You can make the same rough calculation for extensions that add a floor, plus 50 percent. You need to decide whether you're looking for a relatively simple extension, or one that includes adding new plumbing, a kitchen, or other higher-cost items. If its just a simple bedroom you want to add onto your second floor: no problem. But, if you need to dismantle existing walls, change load-bearing walls, or make other structural changes, it is going to cost you. 

3. Extension with kitchen or bathroom

Bright, clean, contemporary Modern style kitchen by homify Modern

Bright, clean, contemporary


For extensions that provide for a new kitchen or bathroom there are further costs. If you want your new bathroom to cost $20 000, for instance, you can only add simple tiles and fixtures, because of the cost of plumbing. For a small and average kitchen you should plan around $40 000, depending on what appliances and other features you want to add. 

4. Extension details

Pebbles Modern style bathrooms by Pixers Modern



If you decide to invest in a home extension, you need to have a particularly beautiful design. After all, floors, lighting, and fixtures set the scene and are indispensable in achieving beauty. High-quality counters for kitchens, top notch bath tubs, great sliding doors, and minimalists features are a must. 

5. What happens in difficult conditions?

modern  by ArchitectureLIVE, Modern

Existing 1900s Family Home in Hindhead, Surrey


Unfortunately, not every expansion is easy to complete. Sometimes there are issues that will require extra planning and money:

- Every expansion needs a solid foundation. Depending on the soil type and conditions, this could be a simple issue, or a tough one.

- Is access to the construction site simple or complicated? Particularly in existing buildings with close neighbours, measures have to be taken, so that workers can reach the construction site.

- Will the structural conditions, walls, roof areas, or windows have to be changed? A roof usually has to be re-done every 12 to 20 years, while windows may not need to be upgraded-- but could save you some money on heating costs if you invest in them. 

- Which pipelines and drainage systems must be modified? If you need to replace weeper tiles (drainage pipes), or the interior pipes throughout a floor, you'll incur significant cost. 

6. Location, location, location

The location of our house plays a bigger role than we might think at the moment. If our family house is in a high-quality location, for example in a good part of a big city or in a district with good infrastructure, it is worth investing a bit more in a renovation. If your house is on-par with the rest of the homes around it, it may not be so advantageous to add an extension. It's always better to meet the expectations a buyer has of your neighbourhood. 

7. Materials and construction

The construction of our extension as well as the materials used can be clearly different from each other. Extensions can also be implemented with very different materials. To some degree, you want to match your existing home, but you can incorporate cheaper or more ecologically friendly materials as well. A ready-to-wall installation is just as conceivable as an extension built from the ground-up. This too is a question of money.

8. How do I manage project costs?

Modern Garden Room Modern style conservatory by homify Modern

Modern Garden Room


In order to manage the project in the best possible way within your time line and costs, it makes sense to involve a professional architect from the outset. Because they have experience in design, they bring in people of all the needed trades and advises about potential hidden costs. For example, an architect calls for 3 to 5 quotes from various tradesmen to compare alternative plans and costs. So we as homeowners have cost security before the actual construction starts. To avoid nasty surprises, it makes sense to set up building contracts between craftsmen and builders. 

by FingerHaus GmbH - Bauunternehmen in Frankenberg (Eder) Modern

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