It depends on where the dormer goes. A modest dormer to the rear of a house is often exempted development, while a dormer to the front, one facing a public road, or one on the roof plane facing the street generally does need planning permission. The dormer is the part of an attic conversion where planning most commonly comes into the picture.
The reasoning behind this is about how the change affects the streetscape. Councils are more relaxed about alterations that are hidden at the back of a house and cannot be seen from the road. A dormer that changes how the house looks from a public vantage point is treated more carefully, and permission is usually required. The size and design of the dormer also matter, so two projects that sound similar can end up with different outcomes.
Because dormer exemption is genuinely case specific, we do not give a blanket yes or no. If your home is a protected structure or in an Architectural Conservation Area, you should assume permission is needed. Where there is any doubt, a Section 5 declaration from Meath County Council will confirm the position formally.
We build both dormer conversions and mansard conversions, and we can advise which suits your roof and whether a planning application is likely. You can learn more in our planning guide or arrange a free assessment. Whether or not planning is required, the finished dormer must still meet Building Regulations.