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Loft Conversions | Portsmouth & Hampshire

The smartest way to add bedrooms without extending your footprint. Building Control approved first time.
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Add Bedrooms Without Losing Garden

A loft conversion is often the most cost-effective way to add living space to your home. You're building within your existing footprint – no foundation costs, no loss of garden, and frequently no planning permission required. But loft conversions are technically demanding. They require careful structural engineering, compliance with fire regulations, and coordination with Building Control at multiple stages. Get it wrong, and you'll face costly remedial work or failed inspections. Crown Construction has completed over 200 loft conversions across Hampshire. Our structural engineer partnerships and ISO 9001 processes mean we pass Building Control first time, every time.

Working towards
ISO 9001
Standards

Which Loft Conversion Suits Your Home?

Velux (Roof Light) Conversions

The simplest and most cost-effective option. Roof windows are installed within your existing roofline, providing natural light without altering the roof structure. Ideal for homes with sufficient head height and where external appearance matters (conservation areas, Listed buildings).

Best for: Good head height, budget-conscious, conservation areas
Typical space: 1-2 bedrooms + bathroom
Timeline: 6-8 weeks | Investment: £35,000-£50,000
Planning: Usually not required

Rear Dormer Conversions

The most popular choice. A flat-roofed dormer extends from the rear of your roof, providing significantly more head height and floor space than a Velux conversion. Since it’s at the rear, it’s usually acceptable under Permitted Development.

Best for: Maximum space, growing families, home offices
Typical space: 1-2 large bedrooms + en-suite
Timeline: 8-10 weeks | Investment: £45,000-£65,000
Planning: Usually not required under PD

L-Shaped Dormer Conversions

An extension of the rear dormer that wraps around the side of the roof. This creates the maximum possible loft space – often enough for a master suite with bedroom, en-suite, dressing area, and study nook.

Best for: Large lofts, master suite conversions
Typical space: Master bedroom + en-suite + dressing room
Timeline: 10-12 weeks | Investment: £55,000-£80,000
Planning: May require planning permission

Hip-to-Gable Conversions

Converts a sloped (hipped) roof end into a vertical (gable) wall, dramatically increasing internal space. Commonly combined with a rear dormer. Essential for 1930s semis and detached houses with hipped roofs.

Best for: Hipped roof properties, semis, detached houses
Typical space: 2 bedrooms + bathroom
Timeline: 10-12 weeks | Investment: £55,000-£75,000
Planning: Usually required

Mansard Conversions

The roof is restructured to near-vertical walls with a flat top. This creates maximum head height and floor space but significantly alters the property’s appearance. Common on Victorian terraces.

Best for: Victorian properties, maximum space, complete roof renewal
Typical space: 2 large bedrooms + bathroom
Timeline: 12-14 weeks | Investment: £65,000-£90,000
Planning: Usually required

Building Regulations Made Simple

Every loft conversion must comply with Building Regulations – there’s no permitted development exemption for this. Here’s what’s required:

Structural Stability

• Floor joists must support bedroom use (not just storage)
• Roof structure must remain stable after alterations
• Steel beams often required for load distribution

Fire Safety

• 30-minute fire-resistant doors to all habitable rooms
• Fire-resistant enclosure around staircase
• Smoke alarms on each floor
• Escape windows or protected stairway to final exit

Stairs

• Maximum pitch, minimum headroom, handrail requirements
• Must provide safe escape route

Insulation & Energy

• Roof insulation to current standards (typically 270mm equivalent)
• U-value compliance for walls and roof

Sound Insulation

• Between loft conversion and rooms below
• Between loft rooms (if party wall with neighbours)

Crown’s approach:

  We coordinate all Building Control inspections and submissions. You
don’t need to understand every regulation – we handle compliance and ensure your
conversion meets all requirements.

Why Structural Engineering Matters

Loft conversions always require structural engineering input. Your existing ceiling joists were designed for storage, not bedrooms. Floor loadings must be increased, roof loads redistributed, and often steel beams installed to create open spaces.

Common Structural Requirements

  • New floor joists alongside existing (doubling up)
  • Steel beams to support roof loads around dormers
  • Steel ridge beams for hip-to-gable conversions
  • Padstones and bearing calculations for steelwork

Crown’s approach: We engage structural engineers during the design phase, not after you’ve committed. This means accurate pricing, no surprises, and drawings ready for Building Control from day one.

FAQ Questions

Frequently Asked Questions

Most lofts can be converted, but the key factor is head height. You need a minimum of 2.2m
from the top of the floor joists to the underside of the ridge. Our free loft assessment will
confirm suitability and recommend the best conversion type.

Ready to Convert Your Loft?

Book a free loft assessment. We'll measure your existing space, confirm structural suitability, and recommend the best conversion type for your home and budget.

Book Your Free Assessment
Call 07816 534 601
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