Glazed Extensions; All you need to know

Glazed Extensions; All you need to know

Hilsdon Holmes can help take some of the stress out of building your dream extension.

What is L1B?

Approved Document L1B (amended 2013) provides guidance on complying with the requirements of Regulation L1 dealing with the conservation of fuel and power. It is one of four Part L Approved Documents and deals specifically with work to existing dwellings.

I’m building an extension, does this apply to me?

If you are building an extension and your plans exceed the area of glazing allowed under L1B 2013 then you will be asked for a letter that demonstrates compliance. So if you want lots of light and have plans for lots of glazing then this will more than likely apply to you…

Why do I need this?

If you have plans for glazing of more than 25% of the new floor area then you will need to compensate by upgrading some of the other elements of the build to get through compliance, we will make this as simple as possible by giving you a few options to look at.

What will you need from me to carry out the calculation?

Construction details and drawings of the whole building, both existing elements that will and won’t be upgraded, along with new elements.

What happens in the assessment?

We will carry out a calculation using the information you have provided us and our software, by, comparing the existing dwelling elements with the proposed dwelling elements.

What happens after the assessment?

Once we have finished the assessment we will write a letter for you to give to your building control officer along with the supporting SAP documents that will demonstrate compliance.


If you would like to discuss your plans with us please call today on 01579 382202 or by email:

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