Loft conversion in Test Valley: Planning Permission Guide
Everything you need to know about loft conversions in Test Valley — permitted development rules, costs, and which professionals you'll need.
Check if your loft conversion qualifiesLoft conversions in Test Valley at a glance
application fee
weeks typical
Test Valley includes or borders the North Wessex Downs AONB — properties in or near those areas are on Article 1(5) land where permitted-development rights are restricted. Test Valley has 33 conservation areas — extensive heritage coverage restricting external alterations across many streets. 2,099 listed buildings recorded.
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Approval probability, 5 nearest comparables, refusal reasons — for your specific address.
Recent loft conversion decisions in Test Valley
The 5 most recent decided applications. Addresses redacted to postcode area.
Proposed side dormer roof extension to existing loft conversion
Conversion of attic space into habitable accommodation, formation of dormer windows to north and south elevations, replace window with do…
Conversion of attic space into habitable accommodation, formation of dormer windows to north and south elevations, replace window with do…
Application for lawful development certificate for proposed conversion of loft and addition of 3 dormers to south elevation and 4 velux w…
Insertion of a dormer window within the north roof slope
These are borough-wide. See the 5 nearest to your address.
Get my report — £9Permitted Development Rules
Additions etc to the roof of a dwellinghouse
GPDO 2015, Schedule 2, Part 1, Class B
Loft conversions fall under Part 1, Class B of the GPDO. You can add volume to your roof space without planning permission, as long as you stay within the cubic metre limits for your property type.
Key dimension limits
These are the maximum GPDO limits for a detached house with no constraints. Your actual limits depend on your property type, location, and any planning restrictions.
Enter your postcode to see the personalised limits for your loft conversion.
Check my limitsTypical Costs in South East England
Loft conversion costs vary significantly depending on the type — a simple Velux conversion is much cheaper than a dormer or mansard.
Cost per m²
construction rate
Typical total
Based on 15–25 m²
Typically includes
Typically excludes
Dormer loft conversions are at the higher end. Velux/rooflight conversions are cheaper. Mansard conversions can exceed these ranges.
Get a personalised cost estimate based on your actual loft conversion dimensions.
Get my estimateWhich Professionals Do You Need?
Loft conversions involve structural alterations to your roof and floor, so professional input is important for safety and Building Regulations compliance.
You'll need a structural engineer and a party wall surveyor for this project.
Loft conversions involve structural alterations and Building Regulations requirements that benefit from professional design.
Typical fee: £2,000–£5,000 (Plans + Building Regs)
Loft conversions require structural calculations for floor strengthening, roof alterations, and any steelwork.
Typical fee: £800–£2,500
Your semi-detached house shares a boundary with neighbours. Extensions and loft work within 3 metres of a shared wall trigger the Party Wall Act.
Typical fee: £700–£1,500 (per neighbour)
This guidance is based on a typical semi-detached house with no special constraints. Listed buildings, conservation areas, and attached properties may require additional professional input.
Find out exactly which professionals you need for your loft conversion.
Get personalised guidanceConservation Areas & Listed Buildings
In conservation areas, dormers on any roof slope facing a highway are not permitted development. Velux or rooflight conversions may still be possible.
Properties in conservation areas often have reduced permitted development rights. Some project types (like side extensions) lose PD rights entirely. An Article 4 Direction can remove additional PD rights.
Listed buildings (Grade I, II*, or II) have no permitted development rights at all. Any external alteration requires Listed Building Consent in addition to any planning permission. An architect experienced in heritage work is essential.
Check if your property is in a conservation area or has other planning constraints.
Check my propertyFrequently Asked Questions
Just want a quick yes/no for your loft conversion?
Run our free 2-minute check to see whether your project likely qualifies as permitted development in Test Valley. For personalised approval odds and nearby comparables, get the full report above.
Free 2-min check