In most cases, converting your attic internally does not require planning permission. If you are simply insulating the space, adding a proper staircase, and finishing the room within the existing roof shape, that work is usually fine on its own. Planning permission tends to come into play when you change the outside of the roof, most often by adding a dormer.
The key thing to understand is the difference between the inside and the outside. Work that stays within the existing roofline is treated very differently from work that alters the roof profile or the appearance of the house from a public road. A modest dormer to the rear of a house is often exempted development, while a dormer to the front, or one facing a public road, generally does need permission. You can read more in our planning permission guide.
There are important exceptions. If your home is a protected structure, or sits in an Architectural Conservation Area, many of the usual exemptions no longer apply and you will normally need permission. See our note on protected structures and ACAs.
If you are not certain, the safe route is a Section 5 declaration from Meath County Council, which formally confirms whether your works are exempt. It is far better to check first than to build and find out later. We can walk you through this as part of our process, and a free assessment is a good place to start. Remember that even when planning is not needed, Building Regulations always apply.