Loft Conversions in Eastleigh: Costs, Planning, and What to Expect
Most Eastleigh homes can have a loft conversion under permitted development rights. Here's what it costs, what's involved, and what adds the most value.
Loft conversions are one of the most popular home improvements in Eastleigh — they add space without extending your footprint and often fall within permitted development rights. Here is what you need to know.
Do you need planning permission?
Many loft conversions in Eastleigh fall under permitted development rights, which means you do not need to apply for full planning permission. Permitted development allows loft conversions that:
- Do not exceed 40 cubic metres (terraced houses) or 50 cubic metres (detached/semi-detached)
- Do not extend beyond the existing roof slope at the front
- Do not project more than 150mm beyond the existing roof slope at the rear
- Do not increase the overall height of the building
If your property is in a conservation area or is listed, different rules apply — check with the local authority before proceeding.
Even if permitted development applies, you will still need Building Regulations approval, and the work must be signed off on completion.
Types of loft conversion
Velux / rooflight conversion: The simplest and cheapest option — Velux windows are added to the existing roof slope without altering the roof structure. Works best where there is already enough headroom.
Dormer conversion: A box-shaped extension to the roof, creating vertical walls and additional floor space. The most common type in Eastleigh's semi-detached and terraced streets. Can be added to the rear under permitted development in most cases.
Hip-to-gable conversion: Replaces the sloping hip of the roof with a vertical gable end, typically used on semi-detached or detached properties. Creates significant extra space.
Mansard conversion: Alters the pitch of the roof significantly to create near-vertical walls. The most extensive type — often requires planning permission.
Typical costs in Eastleigh (2026)
- Velux conversion: £15,000–£25,000
- Rear dormer: £25,000–£45,000
- Hip-to-gable: £35,000–£55,000
- L-shaped dormer: £40,000–£60,000
These are indicative figures. Prices vary significantly based on the size of the conversion, the specification, and the contractor. Always get at least three written quotes.
Party wall agreement
If your home is semi-detached or terraced and the loft conversion involves work on or near the party wall, you will need to serve a Party Wall Notice on your neighbour(s) at least two months before work begins. Your builder or a party wall surveyor can advise.
How much value does a loft conversion add?
A loft conversion with an en-suite bedroom is estimated to add 15–25% to the value of a house. In Eastleigh, given the typical semi-detached stock and proximity to Southampton's employment market, a well-executed dormer conversion can add meaningful value.
Finding builders in Eastleigh
Look for members of the Federation of Master Builders (FMB) — they vet members and provide a dispute resolution service. Checkatrade and TrustATrader also list local builders with verified reviews. Ask specifically for loft conversion experience and references from recent local projects.
Information correct as of May 2026. Planning and building regulations change — always verify with your local authority before commencing work.