Building

Expert advice on structural work, home extensions, renovations and understanding building regulations.

Green Light For Two-Storey Extensions

7th August 2020

Until now, building an extension has required planning permission. However, homeowners hankering to extend their home can now go ahead without getting permission, thanks to new government rules. The easing on legislation is designed to address the housing and care crisis by allowing for extended families to easily live together, and to boost the building and trade industries, which have been left vulnerable by the pandemic.

Exceptions to the rule

If you are planning on extending upwards – wait until after August 31^st, when you can add two extra floors. If you’re living in London, however, it isn’t that simple; the new easing of legislation only applies if you live in a detached home built between 1948 and 2018. Victorian homes, terraces and top floor flats are, therefore, not able to enjoy the new freedom to build.

The bigger picture

Not everyone is celebrating this change in legislation. The practicalities of adding two whole floors – removing the roof and potentially doubling the height of a home – are far more complex than simply adding a loft extension. It takes a skilled architect and experienced builder to undertake such a job, with considerable disruption and at a much higher cost than doing a conversion.

Home transformations that don’t need planning permission

While extending up without permission seems to be a fairly radical concept, this is not the only home transformation that you can do without permission:

Kitchen extensions up to four metres at the back of a detached home or three metres behind a semi or terrace, providing it doesn’t take up more than half of the outside space and uses materials in keeping with the original building.
Two-storey rear extensions of less than three metres, provided that they leave seven metres of garden.
Side return extensions that don’t exceed four metres in height and aren’t more than half of the height of the original house.
Single-storey side extensions of detached homes, provided they are in keeping with the original building.
Loft extensions smaller than 40 cubic metres in terraced homes and 50 cubic metres in terraced or semi-detached homes.
Single-storey outbuildings – some restrictions apply based on the size of your plot.
Front porches are permitted providing they are no bigger than three square metres and are more than two metres from your boundary.

If you want to make the most of your home, speak to an experienced builder. They will have a good idea of what you need planning for, and will be able to offer guidance based on their extensive experience. If you decide not to work with a local architect, it is best to contact your local authority to ascertain that your works are permissible.

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Find clear, practical answers to common building questions, helping homeowners understand everyday issues, know what checks they can carry out safely, and when it is best to contact a qualified professional.

Do I need planning permission for a home extension?

Plenty of extensions don't need planning permission - they fall under Permitted Development. Whether yours qualifies depends on the size, location, and type of build. Single-storey rear extensions up to four metres on a detached house often get the green light, but side extensions, two-storey builds, and properties in conservation areas usually do need permission. Always check with your local planning authority before you start - building without the right approvals can mean being made to undo it all.
What is involved in building a conservatory?

You're looking at groundworks and foundations, the frame and glazing, the roof, and then the internal fit-out - flooring, heating, electrics. Most conservatories under a certain size fall under Permitted Development, but they still need to comply with Building Regulations, especially if you want to use the space as a proper room year-round. On the roof: solid or tiled options make a huge difference to usability - traditional polycarbonate can be unbearably hot in summer and freezing in winter. Most projects take two to six weeks.
Do I need a structural engineer for my home renovation?

Not for everything - but if structural changes are involved, yes. Removing a load-bearing wall, putting in a steel beam, touching the roof structure, or adding a sizeable extension all need a structural engineer to design the solution and produce the calculations for Building Regulations approval. A builder might tell you whether a wall is load-bearing, but only a structural engineer can specify the right beam and carry professional liability for that advice.
Do I need planning permission to install patio doors?

Usually not, if you're replacing an existing door or window in the same opening - that typically falls under Permitted Development. But if you're making the opening larger or creating a new one in an external wall, you may need planning permission or Building Regulations approval. Conservation areas, listed buildings, and properties with an Article 4 Direction have tighter rules, so check before assuming. Any structural work to the opening, like fitting a new lintel, needs Building Regs sign-off regardless.
Does my extension need Building Regulations approval even without planning permission?

Almost always, yes. Planning permission and Building Regulations are two separate things. Extensions need to meet regulations covering structural integrity, fire safety, insulation, ventilation, and drainage - regardless of whether you needed planning approval. Your local authority's building control team can confirm exactly what's required. And don't skip it - missing Building Regs sign-off can cause real headaches when you come to sell.
How long does a typical home extension take?

A small single-storey extension usually takes eight to twelve weeks from groundworks to completion. Add several months if planning permission is needed before work can even begin. Bigger builds - two-storey additions or anything needing significant structural work - can take four to six months or more. Get a realistic timeline from your builder upfront, and factor in a buffer for the unexpected.

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