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Replacing conservatory with extension.

We live in a terraced house. The previous owners added a uPVC lean-to glass conservatory to the kitchen dinning area. This was before building regs stipulated that there had to be a wall between the house and conservatory. The whole room is open plan. The neighbours have the same setup on each side.

We are considering replacing the conservatory with an extension. Building regs says that window/door area should not be greater than 25% of the floor area. Does this apply to just the extension area or the entire open plan room that would be created. i.e. including the original room.

To complicate maters the main drain goes underneath the back to the conservator (Inspection hatch to floor), will this need to be moved? There is no space either side of the house. How much would this add to the project?

You can see the layout here:



2 Answers from MyBuilder Extension Builders

The building regs apply to a conservatory not an extension and are to avoid too much heat loss, if you have a proper extension built there are no restrictions on it being open plan or the door sizes (subject to planning)

I would be more concerned that your conservatory will be on shallow footings unsuitable for your extension

the drain should not be an issue as you can have a triple sealed internal manhole


Answered 15th Jan 2015

With an extension it can be a 'stand alone' and have a large area of glazing. The walls floor roof and glazing need to meet the required u values.
It can be an extension whereby the glazing is permitted to 25% of the floor area plus area of glazing being removed / built over
Where in uk are you ?

Regards. Ian


Answered 5th Feb 2015

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