An architect’s guide to double-storey extensions
If moving home isn’t an affordable option, you might be thinking about building an extension to create the extra space you need. Changes to permitted development laws have made it easier to apply for double storey extensions which gives you the chance to maximise the value of any alterations you make. Our architect’s guide to double-storey extensions covers the basics so you can start to plan your next move.
How much does it cost to build a double storey extension?
Few people have the luxury of not working to a budget, so it helps to have an idea of how much the project will cost before you start. It can be difficult to pin down an exact cost at the start, because fees for architects and contractors will vary, while the materials and specifications of your design will also influence things.
As an estimation, you should expect to pay anywhere from £1,300 to £1,650 per square metre for a basic build. For something in the mid-range, prices vary from £1,650 to £1,900 m², while a top of the range double storey extension can extend from £1,900 to £2,100/m². However, this’ll largely depend on where in the UK you’re located.
You’ll also have to factor in additional costs such as:
Architect fees (approximately 6-12% of construction costs - depending on the level of service provided)
Building control charges (as much as £900 for a 80-100m² extension)
Interior fit out costs
Party wall agreements (which can cost up to £1,000 per neighbour - if under dispute)
Planning application fees (£206 for a double storey extension)
Project management (3-7% of the build cost)
Structural engineer (between £500 and £1,500)
Survey costs (between £500 and £1,500)
Planning Permission
It is more likely than not that you will need to secure planning permission for a double storey extension. If your plan does not meet requirements for permitted development you will have to apply for a household planning permission. You can find the full guidelines needed to achieve permitted development on the Planning Portal.
If a party wall needs to be constructed as part of the build you will need to inform your neighbours and ensure you abide by Party Wall regulations.
How do double storey extensions work with Building Regulations?
No matter what sort of extension work you are carrying out, you need to ensure it complies with current Building Regulations. This involves making an application to the local authority’s building control department or an approved inspector.
This is something that an architect can manage and coordinate on your behalf. Once construction starts the local authority will send a building control officer out to inspect the quality of work to ensure it is up to standard. This guarantees the sustainability and safety of the property so there are no concerns about it being used as a liveable space.
Where can I build a double storey extension?
Where you should build a double storey extension depends on the type of property you live in and the garden space available. Curtilage parking should also be a consideration to ensure that you meet the minimum number of spaces required for the size of your property.
A double storey extension added to the side of your property is ideal if you have a kitchen or bedroom situated there already. As with all extensions, the design of the original house always has to be taken into account, along with the frontage. Working closely with an architect will help you to navigate this part of the design and planning process.
Why should I build a double storey extension instead of a single storey?
The reason most homeowners choose to extend their homes is to add more space. In recent years changes to the law have made it easier for people to add extensions, and with approval times for double storeys now being reduced to 8 weeks (or less) under fast track rules, the process has been simplified.
When deciding between a single or double storey extension, in addition to your personal needs for more space, the value for money should always be at the forefront of your thinking. Don’t forget to consider the money that goes into building the extension versus the potential new value of your home once it has been built.
In the short term, a double storey extension will cost more than a single storey alteration. However, it is still cheaper than moving to a new home and you will also enjoy more value per square foot compared to a single storey extension.
Are you planning a double storey extension?
Building a double storey extension is one of the most cost effective ways to transform your living space and add value to your home. As architects in Cambridge, we can help you plan and build your extension so you can enjoy your home as it grows with you. Get in touch today for a free consultation and we can discuss your ideas in more detail. Call us today on 07984 760 920, email info@tereynarchitects.com or send us a message here and we’ll get back to you.
