Highly Glazed Extension – Orangery – Glass Extension

Glass Extensions , Highly glazed Extensions. Over-glazed extensions, Orangeries. Part L1 B compliance report for Building control  £200.00

Building control usually  require additional evidence if the amount of glazing exceeds 25 %  of the extension  floor area

If you want lots of glass , folding doors that open into the garden , a roof window or lantern  –  we can  prove compliance to building regulations L1B, usually without requiring any special measures.

Some people who  want to build extensions using large areas of glazing are being told by their architects that it cannot be done because the total glazed area of an extension cannot exceed 25% of the new floor area.   This is not true.     If  you choose to demonstrate compliance using the Elemental method then this is  limited to 25 %. However the regulations allow alternative methods demonstrating  compliance which can allow much more glass. Good news  indeed!

A weighted  average U value method could be used in theory but in practice the SAP calculation method  always works much better. We use the SAP calculation method to demonstrate compliance and we often find that we can prove that the the plans our customers submit  usually pass with little or no modification.


Special offer Spring 2016 –  £200 .00 for this service 

For a full quote  send plans (plan, elevations sections and a site plan ) for the  proposed extension and the existing details and we will get back to you with a quote.

In about 5 % of cases some  compensating measures are  required and  there could be an additional charge to evaluate these   – possibly a site visit  may be required.  We will let you know in our quotation if this necessary.   Compensating measures can  often be simple such as upgrading the insulation in the main loft  or other measures that you plan to do anyhow as you upgrade your home.

We have have a 100 % success rate in  getting  our customers proposals approved  – we provide a very comprehensive analysis and  produce a report that provides proof of compliance to building control. This leaves you free to design and build your dream extension without constraints about the amount of glass.


Send details  to Martin.gill@etophouse.com  for a quote

tel 01634 799115 for free advice.

Highly glazed extensions

Modern glass extensions are fast becoming the ultimate in glass design and make a very desirable addition to your home  – however these  require additional proof of compliance to part L of the building regulations  – we can get approval with the minimal amount of fuss and often with no change to the design.  We guarantee that the final design proposal will be acceptable to building control  – otherwise we will refund our fee in full .

We have a 100% record in getting highly glazed or over glazed extensions applications approved through Building Regulations. 100% pass and up to 100% glass! We ensure that your dream extension complies  with building regulations Part L.  We supply an extensive report with a letter of recommendation to building control and full supporting calculations.

We  have found over the years that  the methods that we use and the style of reports that we adopt provides comprehensive evidence that the proposed extension is fully compliant with the regulations and  is fully acceptable to building control. We will provide further support and  follow up queries from  building control if necessary  This is hardly ever required –   because we provide a  very comprehensive report, demonstrating that compliance has been achieved in full.

Why not make your dream extension come true  – don’t compromise on the amount of glass!

Call  Martin Gill on 01634 799115 for free  advice


What is an over-glazed extension?

An over- glazed extension is an extension with substantial amounts of glazing – where the amount of glass exceeds 25% of the floor area – these are sometimes referred to as orangeries . In this case the extension or orangery is no longer compliant on an individual element basis. However the extension can pass L1B regulations using one of the alternative methods. In these cases building control ask for SAP calculations to prove compliance.

Over-glazed extensions could include sun-rooms, orangeries, glass rooms etc. Do not confuse this with the definition of a conservatory – a conservatory in L1B is outside the main insulated walls of your dwelling and is separated by outside quality doors and not heated by the main heating system.

What is required?

  • You or the architect sends us your construction plans
  • We send you a quotation
  • …….if you go ahead…
  • we  do all the necessary calculations
  • We we produce  report with full supporting documentation
  • we  provide you with a list of details to be incorporated into the plans
  • The report is a report of recommendation to building control from our fully qualified assessor  (OCDEA)
  • This is sent out as a PDF in 2 parts

l.  The report  typically contains:

  • Cover / Index
  • Letter of recommendation to building control
  • Key results and conclusions
  • A list of extension details
  • At least 2 full SAP calculations
  • U value calculations
  • Any other supporting documentation and calculations.

We are members of the NHER approved scheme and our calculations are fully acceptable to building control. However the final decision  rests with building control . You should always get them to accept the report and basis of compliance  before proceeding.