When you invest in a garden room, you’re investing in a structure that should be safe, durable and built to last.
At Bexley Garden Rooms, we use a combination of A1 fire rated cement board and OSB (Oriented Strand Board) — each chosen for the specific strengths it brings to the build.
This approach ensures your garden room meets the highest standards of safety, compliance and structural performance, especially for buildings between 15–30sqm and within 1 metre of a boundary, where fire safety regulations become more important.
What Is A1 Fire Rated Cement Board?
A1 cement board is a non combustible, fibre reinforced cement panel with the highest possible fire rating under EN 13501 1.
This means it:
- Does not burn
- Does not contribute to fire spread
- Does not release toxic smoke
It’s the safest material available for areas where fire performance is essential.
What Is OSB — and Why Do We Use It?
OSB is a strong, reliable engineered timber board used throughout the construction industry. It offers:
- Excellent structural rigidity
- Great screw holding strength
- Consistent performance
- A cost effective way to add strength to a wall build up
When used externally in our garden rooms, OSB is fully wrapped in a high performance breathable membrane, protecting it from moisture while allowing the structure to breathe. It’s a proven, dependable material — and we continue to use it where it performs best.
Why Fire Rating Matters Near Boundaries
For garden rooms within 1 metre of a boundary and between 15–30sqm internally, UK building regulations require the external walls to be constructed from non combustible materials.
This is to reduce the risk of fire spreading between neighbouring properties.
Using A1 cement board in these areas ensures:
- Full compliance with building control requirements
- No need for additional inspections
- A safer, more resilient structure
- Peace of mind for you and your neighbours
Some companies still rely solely on timber based boards and hope it won’t be questioned. We prefer to build correctly from the start.
Why We Use a Hybrid System
Rather than relying on a single material, we use a hybrid structural approach:
- A1 cement board where fire performance is required
- OSB where its strength and rigidity are most effective
This gives you the best of both worlds:
- A compliant, non combustible outer structure where needed
- A strong, stable internal build up
- A breathable, protected wall system
- Long term durability without unnecessary cost
It’s a thoughtful, engineered solution — not a compromise.
Built for the British Climate
Our wall system is designed to perform year round:
- Cement board provides exceptional stability and fire resistance
- OSB adds structural strength
- A high quality breathable membrane protects the build up from moisture
- The entire system works together to keep your garden room dry, stable and long lasting
This layered approach is one of the reasons our buildings feel solid, quiet and premium.
Perfect for Offices, Gyms, Studios & Multi Use Spaces
Whether your garden room is for work, fitness, creativity or relaxation, our hybrid system ensures:
- A safe, compliant structure
- Excellent acoustic performance
- Strong, stable walls
- A building designed to last decades
It’s the foundation of a truly premium garden room.
Keeping your builds safe, within regulations and giving you peace of mind
We use A1 fire rated cement board not because OSB is unsuitable — OSB is a fantastic structural material — but because certain locations and room sizes require non combustible construction to meet UK building regulations.
By combining both materials in the right places, we deliver a garden room that is:
- Safe
- Compliant
- Strong
- Durable
- Built properly from day one
It’s a smarter way to build — and one of the reasons our garden rooms stand out for quality and longevity. If you are concerned about where you would like your garden room to go and whether it will fall within regulations, get in touch, we are always ready to help.