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commercial building work

Extending your commercial property

6th May 2021 by Mark Preece

Categories: What's New?

If your business is expanding, you may have outgrown your current premises.  Before you start looking for a new site, it is worth investigating whether you could extend your existing property.  Depending on the site and the nature of your building, you may be able to extend up by adding new floors, down by digging a basement or out, by expanding the footprint of the current building.  As well as complying with planning and building regulations, you must consider any specific legal constraints that might affect your ability to extend.

‘Moving your business will cost you time and money, so it makes sense to get the best out of your existing site if there is room to grow,’ says Mark Preece, head of the commercial property at Laceys. ‘Issues like uncertain boundaries and neighbours’ rights of light can be traps for the unwary, so it pays to get the right legal advice at the outset.’

Check what you own

Before you plan an extension, it is vital to check how much land you own and on what basis.  If you own the freehold, you will generally have more flexibility about making changes. If the property is let as an investment, you must be careful not to interfere with your tenants’ use of it.  Your solicitor will be able to check the terms of your tenants’ leases to see what scope you have for making alterations to any existing buildings and for causing short-term inconvenience to your tenants while works are carried out.  If you have a mortgage, you may also need the lender’s consent for any alterations or additions to the property.

If your property is leasehold, you will probably need consent from your landlord for any alterations.  Many leases have a complete ban on extensions and structural alterations.  Your landlord may agree to your proposals, but you must get consent in the right way.  Getting this wrong could mean losing your lease altogether, so you should make sure your solicitor checks the lease and approaches the landlord for consent on your behalf.  If you want to extend beyond the area already covered by your lease, your landlord may be willing to grant a supplemental lease of additional space. Again, it is important to get this properly documented.

Legal constraints to look out for

Land can be affected by a range of legal issues which could impact on a planned extension.  Some may be set in your title documents and others should be apparent from an inspection of the site.  For example:

  • The property may be subject to restrictive covenants which prohibit or restrict further building on the site or limit the size of any buildings. You might also need the approval of another landowner for any alterations or extension.  In recent years, the courts have taken a hard line on those who deliberately ignore restrictive covenants, awarding damages and in some cases ordering buildings to be taken down.
  • If your proposed extension could block or limit light to the windows of a neighbouring building, you may be able to change the design to avoid problems. If not, you may have to negotiate compensation or get your neighbours to release rights of light.  This is a complex area of law and you should make sure you get specialist advice.
  • It sounds obvious but watch out for your boundaries, as they are not always clear. Land Registry title plans are usually not definitive, so if you are in any doubt, ask your solicitor to check your title documents.  If you extend onto land you do not own, you will be trespassing and could face damages and possibly an injunction.
  • If you are planning to extend upwards or downwards, check whether you own the airspace above and the subsoil below the existing building. The usual rule is that ownership includes as much airspace and subsoil as necessary for the reasonable use of the land, but this may have been limited by specific exclusions when the land was sold or let in the past.
  • Others could already have rights over the area where you plan to extend. Telecoms operators may have rights to keep equipment on the roof; utility companies may have rights to run their services under parts of the site; and neighbours may have rights of way.  If your extension would interfere with any of these, your solicitor will need to negotiate releases or compensation.

How we can help

A successful extension can bring huge benefits in how you use your commercial premises and could help you increase your returns.  Getting a solicitor involved early on will mean you know exactly what you own already and what restrictions you may need to overcome.  This will help you avoid wasting time and costs on unexpected disputes, so you can focus your efforts on putting together a scheme that really works for your business.

If you would like further advice on extending your commercial property please contact Mark Preece in confidence on 01202 557256 or email

This article is for general information only and does not constitute legal or professional advice. Please note that the law may have changed since this article was published.

Mark Preece

Partner — Commercial and Residential Property

Direct dial: 01202 377862


Mark Preece image profile
  • “Mark has acted for our varied property portfolio in Dorset for over 5 years, and has a real understanding of our business and how we operate. He shares our passion for high standards and attention to detail, providing us with invaluable advice and support on all aspects of our developments from initial site acquisition through to completed property sales. Mark and his team continuously add value by being proactive and delivering a fast and expert service."”

    Eddie Fitzsimmons- Managing Director, Lomand Homes Limited

  • “Quick, responsive service. Prepared to recommend a way forward and not sit on the fence.”

    Guy Eccles

  • “Efficient, competent and friendly.”

    Michael Bond

  • “Mark and the team take great care of our commercial property requirements. We have always been delighted with their service.”

    Simon Ward, NSN Propertis Ltd

  • “Straightforward. Everything kept clear and simple.”

    Nicola Maidment

  • “I appreciate the personal service and the feeling that my business is important. I also respond well to a friendly approach.”

    Andrew Taylor

  • “Mark noted the requirements of the sale and worked very hard to achieve an excellent prompt outcome. He phoned me immediately the deal was done!”

    Paul R Barry

  • “Excellent service provided by Mark Preece and his team.”

    Francis & Natalia Erard

  • “Everyone at Lacey's seem to have my best interest at heart and act super efficiently. A pleasure to deal with.”

    John Beauchamp

Mark qualified as a solicitor in 2008 after gaining an LLB (2003) and LLM (2005) at university’s in Birmingham.  He completed his training contract with the North Dorset and South Wiltshire firm now known as Farnfields LLP and joined Horsey Lightly Fynn (HLF) in Bournemouth in 2011.  He became a partner at HLF in 2014 and at merger of HLF and Laceys became a partner in the merged firm in 2015.

Mark is a partner working across our Commercial and Residential property teams acting for a wide variety of clients from property developers, property investors, businesses, first time buyers and those needing advice relating to enfranchisement and residential landlord and tenant dealing with all aspects of property work.

Away from work Mark spends his time with his wife and their three young boys who keep them very busy.

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