You may or may not need planning consent, depending on whether your home is listed or in a conservation area, and how much of the chimney you want to remove.
As chartered surveyors in London, we see many properties where only part of the chimney breast has been removed, for instance just ther ground floor, or up to the loft.
No matter what your builder says, you will need to have this done in accordance with Building Regulations. When you come to sell, your buyer (often prompted by his building surveyor) should ask to see your certificate of building regulation approval. If you don't have one, you may face losing your sale or opening up your structure to show that it was done properly.
When considering whether a chimney breast removal was done satisfactorily, our chartered surveyors will not only look at how the remaining chimney is supported but also damp prevention, fire regulations and ventilation.
Particular care needs to be taken when the wall is a Party Wall with a neighbour. In this case, some methods of support, for instance Gallows Brackets (see diagram) or corbelling are not considered suitable and the Party Wall Act will need to be followed.
In the photograph, you can see where a chimney breast has been removed up to the loft, and then supported on a small piece of timber. As the timber weakens, usually by wood rot over years, it's collaps will send what remains of the chimney stack crashing into the bedroom below. Thankfully, this unsuspecting home buyer had a House Purchase Survey by one of our team of structural surveyors.
For full advice on the type of survey you should have when removing a chimney breast, contact Woodward Chartered Surveys in London.