SAP Calculations for Extensions

Many extensions or renovations are light-hungry, utilising large areas of glazing as an integral part of the design. If so, Building Control will require Part L1b SAP Calculations.

Part L1b regulations state that no more than 25% of the new floor area should comprise glazing. If you are worried that your extension, or renovation design does not comply, we can help you to overcome the problem.

How Can Hilsdon Holmes Help with SAP Calculations for Extensions?

We have experienced this particular problem in a number of builds we have consulted on. We advise clients that they should upgrade or over-compensate on other elements – perhaps by showing the solar gains achieved – in order to neutralise the negative impact of large areas of glazing.

If you are upgrading an existing property, and your extension, or renovation is part of a larger project, you may be able to offset problems in one area by providing sustainable efficiencies and upgrades elsewhere. You have options – and we are happy to guide you through them.

SAP regulations also apply to many change-of-use schemes, such as commercial-to residential , or house-to-flat conversions.

We Specialise in Part L1b Calculations

Hilsdon Holmes has the expertise to help you through Part L1b Regulations. We’ve provided bespoke solutions for thousands of build projects throughout the UK. We’re in the business of finding a solution that is right for you – without you having to change your plans.

Planning a build is a complex and often stressful process. We want to help make life easier, so we can deal with your Building Control Officer and take care of your Part L1b SAP Calculation – it’s what we do best!

  • Do you need to know more about Part L1b?
  • Do you need SAP Calculations for new build?
  • Would you like to discuss your extension or renovation project?

Just give us a call on 01579 382202 for further info on SAP Calculations for Extensions, or email us at

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