Types of loft conversion
There are four main types of loft conversion:
Velux (rooflight) conversion โ The simplest and lowest cost option. No structural changes to the roofline; existing roof timbers are reinforced and roof windows are installed. Only suitable if the roof pitch is steep enough (typically 40ยฐ+) and the head height is sufficient.
Dormer conversion โ A vertical extension to the rear roofslope creates a box-like structure with full-height headroom. The most popular type in Wales, suitable for most property types. Provides more usable space than a Velux conversion.
Hip-to-gable conversion โ Used on properties with hipped roof ends. The hipped end is replaced with a vertical gable wall, extending the usable floor area. Often combined with a rear dormer.
Mansard conversion โ A major structural alteration that replaces the rear roofslope with a near-vertical wall and shallow-pitched roof. Provides the most space but is the most expensive and requires planning permission.
Loft conversion costs in Wales 2026
Wales loft conversion prices are typically 10โ20% below London and Southeast England equivalents.
| Type | Typical cost range |
|---|---|
| Velux/rooflight conversion | ยฃ18,000โ32,000 |
| Standard dormer (rear) | ยฃ28,000โ50,000 |
| L-shaped dormer | ยฃ35,000โ60,000 |
| Hip-to-gable | ยฃ32,000โ55,000 |
| Mansard | ยฃ45,000โ75,000 |
These costs include structural works, insulation, a staircase, electrics, plastering, and a basic finish. They exclude:
- Architect or structural engineer fees (typically ยฃ1,500โ4,000)
- Party wall agreements (ยฃ700โ1,500 per neighbour)
- Building regulations approval (ยฃ500โ900 for Cardiff, Newport, Swansea)
- Internal fixtures, bathroom suite, and decoration
Cardiff and Newport sit at the higher end of the Wales range. Valleys towns (Merthyr, Pontypridd, Rhondda) are typically at the lower end.
What affects the price?
Staircase access โ A new fixed staircase is always required for a habitable room conversion. Its location within the existing floorplan can be a significant constraint, sometimes requiring an existing bedroom or landing to be reconfigured.
Head height โ The minimum usable head height in Wales under Building Regulations is 2.0m (over at least 50% of the floor area). Properties with lower ridge heights may need structural modifications.
Structural condition โ Older properties with non-standard roof timbers (cut roof vs trussed rafter) affect conversion complexity and cost. Trussed rafter roofs (common in post-1960s homes) require more structural work than cut roofs.
En-suite bathroom โ A wet room or en-suite in the conversion adds ยฃ4,000โ8,000 depending on specification.
Fire safety and escape โ Building Regulations require a protected escape route in a house with a new habitable storey. This often means upgrading fire doors and detection throughout the property.
Planning permission in Wales
Most loft conversions in Wales are Permitted Development โ meaning no planning application is needed. However, this does not apply if:
- The property is a flat or maisonette
- The property is in a conservation area or is listed
- The conversion changes the height of the ridge
- The front roofslope is affected
A Mansard conversion always requires planning permission. Hip-to-gable conversions sometimes do, depending on the local planning authority.
Building Regulations approval (separate from planning permission) is always required for loft conversions. This covers structural, fire safety, insulation, and staircase requirements.
Party wall agreements are required if the structural work is within or on the party wall โ relevant for terraced and semi-detached properties.