Conservatory Building Regulations - Changing your windows
Building Regulations
Choosing the right company when buying a conservatory or windows and doors, can take the hassle out of organising Building Regulations and Planning Permission.
Building Regulations & Compliance Guide
At KJM Group, we believe in transparency. Understanding the difference between Planning Permission (how it looks) and Building Regulations (how it performs) is vital for protecting your home’s value. This guide covers the essential 2026 standards for roofs, windows, and energy efficiency.
Contents:
1. Why Compliance Matters
Building Regulations are not just "red tape"—they ensure your home is safe, dry, and energy-efficient. Failing to comply (for example, by using an unregistered installer or a cheap cladding system) has serious consequences:
- Insurance Voids: If a non-compliant roof collapses or causes a fire, your home insurance may refuse to pay out.
- Resale Issues: Solicitors will demand a Completion Certificate for any structural work. Without one, you may be forced to pay for an expensive "Regularisation" inspection or indemnity insurance.
- Enforcement Notices: Local councils have the power to force you to demolish illegal work at your own expense.
2. Conservatory Roofs & The "75% Rule"
This is the most critical regulation for 2026. Historically, conservatories were "exempt" from building regulations if they had independent doors and a heating system separate from the house. Crucially, they also required 75% of the roof to be translucent (glass or polycarbonate).
⚠️ The Solid Roof Trap
The moment you install a solid tiled roof, you no longer meet the 75% rule. The structure is legally re-classified as an extension. Therefore, you legally MUST obtain Building Regulations approval for structure and insulation.
Many "clad-over" systems ignore this, leaving you with an illegal structure that traps moisture and creates a fire risk.
➡ READ MORE: The Dangers of Over-Cladding Conservatory Roofs
The Solution: A Certified Warm Roof
To comply with Part L (Thermal Efficiency), the new roof must meet a U-Value of 0.15 W/m²K. At KJM, we remove the entire existing roof structure before installing a brand-new, highly insulated Conservatory Warm Roof system.
3. Windows & Doors (FENSA & Part F)
Since April 2002, all replacement glazing in dwellings must comply with Building Regulations. KJM Group is a FENSA Registered Company, meaning we handle all certification for you.
- ✓Part L (Thermal): Windows must meet specific U-values to reduce heat loss.
- ✓Part N (Safety): Toughened safety glass is mandatory in doors and windows within 800mm of the floor.
- ✓Part F (Ventilation): A crucial update. Most replacement windows must now include Trickle Vents to ensure background ventilation and prevent mould, unless you can prove your home has a mechanical ventilation system.
- ✓Fire Egress: Replacement windows in bedrooms must provide an escape route equivalent to or better than the original window.
4. Solar Panels & Structural Load
In many cases, fixing solar panels to a roof is 'Permitted Development'. However, from a Building Regulations perspective, you must consider Part A (Structure).
Just like a warm roof, solar panels add significant weight. The roof structure must be checked to ensure it can carry the load of the panels plus wind and snow loads. This is particularly important for older properties with lighter roof trusses.
5. Need Detailed Planning Advice?
Remember: Building Regulations are about safety. Planning Permission is about size, appearance, and neighbours. For a detailed breakdown of size limits (3m vs 4m rules) and permitted development rights, please read our dedicated guide:
📝 The KJM Planning Service
Confused about the 3-metre rule, neighbour consultation, or Conservation Areas? Read our blog guide:
Frequently Asked Questions
A FENSA certificate is your proof that your window or door installation complies with building regulations. It is registered with your local council and is essential when selling your home.
Flats do not have Permitted Development rights. You should check with your Local Planning Authority. If you are a leaseholder, you also need permission from the management company or freeholder.
If you are replacing a glass/polycarbonate roof with a solid 'Warm Roof', the new roof must meet a U-Value of 0.15 W/m²K to comply with Part L Building Regulations. Glass roofs have different standards.
📚 Knowledge Hub: Further Reading
Stay informed about the latest standards affecting your home improvement projects:
- The Future Homes Standard 2025 What the new government energy targets mean for your windows and doors.
- The Role of Trickle Vents Guide Why ventilation is now mandatory for replacement windows to prevent mould.
- Definitive Guide to Window Replacement Everything you need to know before upgrading your glazing.
- Conservatory Planning Permission Guide Understand Permitted Development rights, size limits, and conservation areas.
Ensure Your Project is Compliant
Don't risk your home with non-compliant solutions. Trust KJM Group to handle the planning, the build, and the certification.
