Adding a house extension: The rules, costs, and ideas | homify
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Adding a house extension: The rules, costs, and ideas

Johannes van Graan Johannes van Graan
House Beswick Modern houses by Hugo Hamity Architects Modern
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Adding an extension to an existing house can be tricky and costly. But don’t fret if you don’t have any understanding about the rules and regulations (such as Planning Permission, what type of extension would be best to introduce more natural lighting / practical legroom, or how much house plans cost in South Africa) – homify has got you covered!

Thus, today we take a look at some vital factors to consider before you phone up an Architect to help you with your dream home / extension. This is not only to inspire you in case you want to extend your house upwards, but also to ensure you gain an understanding of the cost of drawing up house plans in South Africa, the proper planning technique and discipline that pertain to building extensions, etc.

1. A house extension project: Extending it upwards

A house extension doesn’t just mean adding an additional room on the side of the main structure. For example, you can also go up and create or add to the second storey. 

Of course this would mean you’ll require the appropriate building plans of both your existing home and your planned extension (whether you live in the city of Cape Town, Pretoria, or anywhere else in South Africa). 

If your house’s roof is sufficient, you might even be able to convert it into an attic room, something which is not that common in South Africa. Or else you could add a separate free-standing structure (i.e. a garden cottage) that links to your main house.

Remember that just because your local authority isn’t bothered by style or design (if you live in a free-standing home in an open neighbourhood as opposed to a security complex), this is still an essential element to ensure your extension looks good. The materials of your extension need to match or complement your existing house’s (such as brick, concrete, wood, etc.). And if it’s plastered and painted, matching the paint colour is advised.

2. Planning Permission in South Africa

The law states that homeowners in South Africa must have their plans for any new building or renovation project for their property approved by the relevant local authorities. This also includes smaller building projects such as adding a new wall around your property or building a swimming pool. 

So, remember to liaise with the planning department of your local municipality to enquire about Planning Permission before you proceed with anything. The best way to do this is by appointing a qualified architect or draughtsperson to draw up and submit the building plans to the local municipal planning department.

And bear in mind that there’s also a fee attached to this process. Therefore, for smaller home extensions, a draughtsperson would be the more cost-effective option. 

3. Proper planning before starting an extension

Modern houses by REIS Modern

Lots of homeowners undertaking an extension project plan for future add-ons, which makes it much easier for adding on more rooms or converting space in the future. A typical example would be building a lintel at a point where a future door is to be placed, and then enclosing the door area with straight joints. This makes it easier to knock out the brickwork later on. And the fact that the bricks aren’t bonded beneath the lintel is not a problem, for the lintel will support those above.

But it’s still very important that you ensure your extension is correctly executed, with the proper foundations (unless you are extending your house upwards) and where brick or block walls meet (these must be bonded or joined properly to avoid cracking the structure).  

4. How much does an extension cost?

How much you will pay for a house extension will depend on what you want. Of course it’ll be cheaper to go with smaller and less complex projects, and opt for more cost-effective finishes and materials. Therefore, the costs of any two kitchen extensions, two-storey builds, or single-storey add-ons will never be the same. 

Don’t forget about location: drawing up building plans in the City of Cape Town or Johannesburg, for example, will likely result in higher costs for your extension project than one in a smaller town.

Another important element to consider with a house extension is the demolition work (and the associated costs) required. With demolition, the services of several professionals will be required such as carpenters, painters, plasterboard experts, etc. And depending on the type of room you are demolishing / adding, other experts like electricians, plumbers and tilers might also need to become involved. Never forget to account for these costs in your project’s budget. 

homify hint: How much do house plans cost in South Africa? Well, before starting on a house extension project, consult with professionals (such as an architect and land surveyor) to ensure your project is properly planned. Fees usually range anywhere from 4%—12% of the construction cost. Bear in mind that the professional’s fees will depend on the size of the company, expertise, qualifications and level of service they provide. As a rule of thumb, a structural engineer’s fee could be about R150 / m².

5. Different types and designs of house extensions

Of course you should also have a clear idea of what you want to achieve with your house extension, whether it’s adding more legroom, increasing your home’s natural lighting levels, etc. Some of the more popular ideas are:

• Building a core house and adding extensions later on according to existing plans

• Transforming a garage into additional living space

• Building an attic or converting an existing one into a habitable space (like a guest bedroom)

• Constructing rooms in a roof with no attic

• Adding or converting a cellar, which could be used for anything from storing wine to functioning as a games’ room for children

• Adding a conservatory, sunroom or pool room (especially by using lots of glazing to allow for maximum sunshine indoors). 


Why do people extend their houses?

The most popular reasons why homeowners opt to extend their houses upwards (or sideways) are:

• To include additional space in their homes

• Due to family members moving in (i.e. helping grandparents with live-in care)

• To boost the property’s value

• So that they won’t need to move away from their neighbourhood

• To avoid the stress that comes with moving house.

The pros of adding a house extension

Room for creativity: If you have an idea of what you want to achieve with your home extension (and you have the appropriate budget), you can eagerly chat with an Architect in South Africa to help you draw up house plans.

More space immediately: If limited legroom is your only issue, then there is no reason why extending your house upwards or sideways can’t gift you with that new guest bedroom (or art studio, or conservatory… ) you’re dreaming of. 

Added value: The rule of thumb states that the more square footage your property has, the higher it’s valued. Thus, building a home extension now and then selling your home later on could mean you earn back what you spent on your extension – perhaps even more. 

Up next: Top 20 modern kitchen designs in South Africa


So, what will YOUR house extension be used for?
Modern houses by Casas inHAUS Modern

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