Can you Extend an Extension Without Knocking Down the Original? Information, help and advice on many architecture, self build and design problems and issues

[digitalmoe]

Hello...this is my first post.

I have a end terrace house which currently has a 3 meter rear extension...I have contacted the local authority and asked them if I would be able to extend it another 3 meters to make it a full 6 meter rear extension...the LA advised I could and this would fall into permitted development if carried out by March (or so) 2019.

What I would like to know is...is it possible to extend an existing extension without demolishing it and starting again? ...I just want to make the the rear extension longer...currently it has a flat roof and I would prefer to have either a pitched roof with skylights with a flat roof with lanterns.

...would it be the case of knocking down the rear wall/windows and just extending on from the current structure? ...any help would be appreciated so I can plan for the build and factor in the costs etc.

Property is in London.

Thank you.

[michaelscad]

if you posted more details perhaps i may be able to help, remember you're
probably only going do this once so think about maximising the project
i've got plans and a project management spreadsheet for period terraced rebuild

[ronan01]

Yes, it is possible to extend like you said but it would be advisable to take professional building contractor's help or an architect. As for building extensions, you will need a party wall agreement if you have a neighbouring wall attached to your property.