Building a roof terrace: structure, permit and approach

Building a roof terrace starts with two questions: can the roof carry the weight, and do you need a permit? On the flat roof of an extension, garage or upstairs flat a lot is often possible, but a roof terrace is more than decking on the roof. It needs a safe balustrade, a good roof covering underneath and access, for example through a roof extension or dormer. In Amsterdam we built a roof terrace with a timber roof extension. Below you can read how it works.

Is my roof suitable for a roof terrace?

A flat roof is usually designed for snow and maintenance, not for a terrace with furniture and people. A structural engineer assesses whether the joists or the concrete deck can carry the extra load. Sometimes strengthening is needed, or a structure that transfers the weight to the walls.

Look at the roof covering too. A terrace on an old bitumen or gravel roof is asking for leaks. It is often wise to renew the roof covering first.

• Have the load capacity assessed by a structural engineer
• Roof covering in good condition, or renew it first
• Enough fall for drainage
• Safe access to the roof

Do you need a permit for a roof terrace?

Often yes. A roof terrace with a balustrade usually requires a permit, because the appearance changes and it creates a view into the neighbours' property. Whether it can be permit-free in your situation depends on factors such as the location, the height and the municipality's environment plan.

Also consider neighbour law: within two metres of the boundary you are generally not allowed to create a view onto the neighbours' property without their consent. Always check with the municipality or via the Omgevingsloket. Read more in permits for a renovation and roof extension permit.

How is a roof terrace built up?

A supporting structure goes on top of the roof covering, for example adjustable paving supports or timber joists on rubber blocks, so the roof covering is not damaged. The floor goes on top: timber or composite decking boards, or tiles.

A balustrade goes all around. Under the building regulations, a guarding at a height difference must generally be at least 1 metre high, and higher at greater heights. Glass, timber or a brick upstand help set the atmosphere.

• Paving supports or joists that protect the roof covering
• A floor of timber, composite or tiles
• A balustrade at least 1 metre high
• Keep drainage clear and accessible

Can you combine a roof terrace with a roof extension?

Yes. In the centre of Amsterdam we built a timber roof extension on a flat roof, with timber cladding and a frame with a door, plus timber decking next to it as a roof terrace. At first there was a bare gravel roof. The old roof covering was removed, then the timber frame was built and the decking laid. You can see the project at the roof terrace with roof extension.

A roof extension gives extra space and at the same time dry, easy access to the terrace. Read more about this combination under roof extension and roof terrace.

What does building a roof terrace cost?

The costs depend on the size, the structure, the floor, the balustrade and the access. A simple terrace on a strong flat roof is something quite different from a terrace with strengthening, a new roof covering and a roof extension. You will find rough ranges at what does a roof terrace cost.

We like to start with a visit, so we can look at the structure and the possibilities together. After that you receive a tailored quote.

Frequently asked questions