The High Life: A Guide to London Roof Terraces

Planning Permission: The Two Big Hurdles

A common misconception is: "It's my flat roof, I can stand on it." This is incorrect. Converting an existing flat roof into a terrace constitutes a "Material Change of Use." You absolutely need Full Planning Permission.

Planning officers will scrutinize two main things:

1. Overlooking (The 1.7m Screen)

The council protects your neighbours' privacy aggressively. If you can stand on your roof and look down into their garden or bedroom, the application will be refused.

To mitigate this, we usually have to design **Privacy Screens**. These are typically 1.7 meters high and usually made of obscured glass (sandblasted) or timber louvres angled upwards. This prevents you from looking down, but still allows light to pass through. It can turn your terrace into a bit of a "box," but it is often the price of permission.

2. Noise

If your terrace is near a neighbour's bedroom window, the council may worry about party noise. They might restrict the size of the terrace (pulling it away from the edge) or add conditions about no amplified music.

Balustrades: The 1100mm Rule

Safety is non-negotiable. Building Regulations (Part K) state that for any drop of more than 600mm, you must have a barrier.

• Height: The handrail must be at least 1100mm (1.1m) above the finished deck level. This is higher than most people expect.
• The 100mm Sphere: There can be no gaps anywhere that a 100mm sphere (a baby's head) could pass through.
• Climbability: You cannot have horizontal bars (like a ladder). The design must be unclimbable. Glass or vertical railings are the standard choices.

Structure and Weight

A flat roof designed to keep rain out is not necessarily designed to hold a party of 20 people. Most timber flat roofs usually need reinforcing to become "load-bearing floors."

Fire Safety: The Post-Grenfell Shift

Since the Grenfell tragedy, regulations regarding combustible materials on balconies have tightened dramatically (Regulation 7). If your building is over 11 meters tall (roughly 4 storeys), you **cannot use timber decking**. You must use Class A fire-rated materials.

Even on lower buildings, we strongly advise against timber. It rots, it gets slippery, and it is a fire risk. The modern standard is:

• Aluminium Decking: Powder-coated, non-slip, non-combustible, and cool to the touch.
• Porcelain Pavers: 20mm thick tiles that sit on plastic pedestals. They look like stone but are lighter and fireproof.
• Composite Decking: Warning—many composites are plastic-based and burn. Only use Class B fire-rated composite if permitted.

Waterproofing: EPDM vs GRP

The biggest fear is leaks. Because you are covering the roof with decking, fixing a leak is a nightmare (you have to lift the whole deck).

We recommend **EPDM (Rubber)**. It is a single sheet of synthetic rubber glued to the deck. It has no joints to fail and is flexible, moving with the building. It lasts 50+ years.

**GRP (Fibreglass)** is also popular, but it is rigid. If the timber deck moves or cracks, the GRP can crack too. It is better suited to small, rigid concrete balconies.

Felt is the budget option. Avoid it for terraces. It becomes brittle in the sun and has multiple seams that are prone to failure.

Access: The Pod vs The Hatch

How do you get up there?

The Glazed Pod (The Dream)

A sliding glass box that feels like walking up into the sky. It brings huge light into the stairwell. However, it adds height and bulk to the roofline, which planners hate. It is difficult to get approved in Conservation Areas.

The Hydraulic Hatch (The Stealth Option)

A low-profile glass rectangle that opens on gas struts (like a car boot) or partially slides. When closed, it is barely visible from the street. This is your best bet for planning approval.

Summary: A Room Without a Ceiling

A roof terrace flat is the ultimate London asset. It adds 20-30% to the value of a top-floor apartment.

But do not cut corners on the "boring" stuff. The waterproofing detail at the door threshold (the upstand) is critical. The structural calculations are critical. The handrail fixings are critical. Enjoy the view, but build it on a solid foundation.