Possible to put new roof on older extension??

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Am buying a 1930s terrace that has a brick single story rear extension with a flat roof. Guessing it was done a couple of decades ago. I’ve not had a surveyor/builder in yet, but am hoping it’s possible to replace the roof to one with a shallow slope and roof lights, and put the dining area / part of the kitchen in there. Ie basically upgrade the existing rather than having to knock down and build new. Anyone have any experience of doing this / possible costs / whether it’s not even a thing?? Thanks

I've not done this but you will need at least building regulation approval, so plans drawn up for you. If there is a new drainage connection you may need planning permission but again definitely building reg approval. So if putting part of the kitchen in there you might not want to move a sink.

Building reg people might like a higher roof but you'll need to consider insulation as modern standards are higher.

You may need raise or make smaller the upstairs windows to get the correct pitch

Thanks both. Next door has a similar extension but with a pitched roof that fits under existing windows, so would be looking replace with similar.