- A standard conversion keeps the existing roof shape and uses rooflights.
- A dormer conversion extends the roof to add usable floor area and headroom.
- Planning treatment is different — dormers may fall under a specific exemption from 27 July 2026.
- The right choice depends on headroom, roof shape, layout and how the room will be used.
The two routes in one sentence
A standard attic conversion works within the existing roof profile and brings light in through rooflights. A dormer conversion extends part of the roof outwards, creating a flat-ceilinged area with a vertical window — adding both floor area and standing headroom.
Side-by-side comparison
| Consideration | Standard conversion | Dormer conversion |
|---|---|---|
| External roof profile | Unchanged | Extended on one or more slopes |
| Usable floor area | Limited to the existing volume | Increased where the dormer is added |
| Standing headroom | Only where the ridge is high enough | Full standing height under the dormer |
| Natural light | Rooflights only | Rooflights plus vertical dormer windows |
| Planning | Often within existing exemptions | Subject to the 27 July 2026 conditions or a planning application |
| Structural work | Usually lighter | Heavier — new structural openings in the roof |
| Disruption | Lower — the roof envelope is largely untouched | Higher — a section of the roof is opened during construction |
| Suitability | Best where the ridge is high and the plan is generous | Best where a room requires standing headroom throughout |
When a standard conversion is the right answer
Standard conversions are often the cleanest solution where the existing roof has generous headroom and a straightforward shape, where the intended use is a bedroom with sloped ceilings, a home office or a playroom, and where the exterior of the property is best left unchanged for planning or aesthetic reasons. Rooflights positioned carefully bring enough daylight for most uses.
When a dormer makes sense
A dormer usually comes into consideration where the roof does not offer enough standing headroom over the full room, where a bedroom needs an en-suite and the layout demands more floor area, or where the home has a hipped roof that would otherwise pinch the useable space at the sides. It also opens up wider window views and vertical light that a rooflight cannot match.
Design considerations beyond size
- How the dormer relates to the front elevation of the house.
- How it reads from the street and from neighbouring gardens.
- The material of the cheeks, roof and window — zinc, tile-hung, render, slate or metal.
- The internal ceiling condition — flat, coombed or a combination.
What this means for your project
Neither route is universally better. The design decision follows the survey, once the roof shape, headroom, layout and intended use are understood together. A well-designed standard conversion can outperform a poorly conceived dormer — and vice versa.
What this means for your project
Every home is different. Use this guidance to ask the right questions and to shape your brief — but confirm what applies to your specific property with a home survey and appropriate professional input.
Frequently asked questions
- Which is cheaper?
- A standard conversion usually involves less construction than a dormer, but published price ranges are unreliable — the cost is driven by structure, services, finish and site access, which vary by property. A site survey and a written quotation are the only reliable way to compare.
- Which gives more space?
- A dormer typically gives more usable floor area and standing headroom, particularly in hipped roofs and homes with a low ridge. A standard conversion is limited by the existing roof profile.
- Does a dormer always need planning permission?
- Not always. Certain rear and side dormers may qualify for exemption under the 27 July 2026 update, subject to conditions. Front dormers and works to Protected Structures typically require planning.
- Can I start with a standard conversion and add a dormer later?
- In principle yes, but in practice it is usually more efficient to decide at the beginning. Adding a dormer later means opening the roof and reworking finishes that have already been completed.
Start with a quick check of your attic.
Answer a few simple questions about your home and what you would like to create. We’ll give you an early indication of which conversion route may be worth exploring. A home survey is still required before suitability can be confirmed.
Or call +353 85 150 0853