Residential Extensions
Specialists in overglazed extension calculations
New Build, Conversions and Extensions

When building a residential extension, if the area of glazing exceeds 25% of the new floor area you will be required to show compliance with Part L1B of the Building Regulations 


At E & S Bristol we have provided calculations for building control approval on a wide variety of residential extensions including basement excavations, pool houses, orangeries and conservatories open to the dwelling.

  • Irrespective of the amount of glazing,  E & S Bristol will you propose a workable solution in line with your design

  • As part of our service we will provide U-Value calculations for all new thermal elements

  • We will make recommendations to reduce the CO2 emissions associated with the extension and if required the existing dwelling  

  • We will provide notional and proposed SAP calculations along with a summary letter for building control explaining how requirements have been met

Get in Touch

We are just a phone call away!

Give us a call and we can give free impartial advice or a quote to complete your
Part L1B Extension Calculations


Call: Marcus on 07517 339990 or Graham on 07517 339991


Complete our contact form here