Garage Conversions: Turning Cold Storage into Living Space

Converting a garage into habitable accommodation is one of the most cost-effective ways to expand your home. Here's what you need to address to meet the standards and obtain a final sign off certificate.

🧱Foundations & Floor Upgrades

Garage floors are usually thin concrete slabs with poor insulation. To comply with Part L (Thermal Performance), you’ll need:
• A damp-proof membrane (DPM) to prevent rising moisture
• Rigid insulation (typically 75–100mm PIR board)
• A new screed or floating chipboard floor finish

In some cases, the existing slab may need strengthening if it’s cracked or too thin to support walls and loads.

🔥 Walls, Insulation & Fire Separation

External garage walls are often single-skin brickwork—cold, damp, and thermally inadequate. Solutions include:
• Adding insulated studwork (timber frame with PIR or mineral wool) and vapour control layers
• Installing insulated plasterboard directly onto walls in tight spaces

If the garage adjoins the main house, the wall between them must provide 30 minutes of fire resistance under Part B. This often means upgrading with fire-rated plasterboard and ensuring all penetrations (pipes, wires) are properly sealed.

🪟 Windows, Doors & Ventilation

Replacing the garage door with a window or wall infill requires careful detailing:
• Use cavity wall construction or insulated studwork to avoid cold bridging
• Fit double-glazed, low-E windows that meet Part L U-values
• Ensure adequate background and purge ventilation, especially if adding a bathroom or utility room

Any new external door must meet Part M (Accessibility) requirements for width and threshold heights.

🚽 Services & Drainage

Adding a bathroom, WC, or utility room to a garage conversion introduces further complexity:
• New soil pipes may need trenching across driveways or gardens
• Existing foul drainage must be checked for capacity and condition
• Mechanical extract fans are required in wet rooms to meet Part F (Ventilation)

Electrics must be designed for increased load and comply with Part P, with certification from a qualified electrician.

📐 Planning Permission vs Building Regulations

Most garage conversions do not require planning permission, provided you’re not enlarging the building. But you will need Building Regulations approval covering:
• Structure (floors, walls, and roof where altered)
• Fire safety and separation
• Thermal insulation and damp-proofing
• Drainage and ventilation

As with lofts and extensions, obtaining approval through Building Control provides peace of mind for resale and mortgage applications.

💸 Costs & Value Added

Garage conversions are typically cheaper per square metre than extensions, because you’re repurposing existing structure. However, costs vary depending on:
• Floor upgrades and insulation levels
• Whether plumbing and drainage are required
• Quality of finishes (basic study vs full bedroom with en-suite)

On average, expect £1,000–£1,800 per m² in 2025. A well-designed conversion can add significant value to your property—especially when creating an extra bedroom or home office.

🛠️ Final Thoughts

Garage conversions are deceptively simple projects that can quickly become complex without the right advice. At Building Regulations Associates, we prepare the plans, submit to Building Control, and liaise with inspectors—ensuring every detail is compliant, efficient, and tailored to your home.

Let’s turn your cold garage into a warm, functional living space.