Can Planters Sit Directly On An Insulated Roof Terrace Layer?

While the answer to this often-asked question isn’t a categorical no, we wouldn’t normally advise placing any planter directly on top of an insulated roof layer as this can cause problems.

To begin with, all flat roofs have a slight fall to allow for drainage. As the insulated roof layer is of constant thickness this pitch is continued, so a planter and base placed directly on top of it won’t stand perpendicularly. Without any means of levelling the planter, this misalignment will be very noticeable when compared alongside other vertical surfaces.

On the subject of drainage, planters need to allow for this to promote good plant health, but placing a planter with an integral base or a planter wall system with enlarged footplattes directly onto the membrane may inhibit drainage. It also increases the risk of roots growing out through the drainage holes and penetrating the membrane, causing damage that will affect its waterproofing and insulating properties, and eventually require replacement.

There is also an increased risk that the membrane will be damaged by the sharp corners of a planter or planter wall during installation. Over time, the combined weight of the planter and its contents can cause membrane damage. As the planter cannot be fixed down securely without penetrating the insulated roof layer, lateral movement can also be a cause of damage to the membrane.

So what is the solution?

Terrace System Installation on Insulated Roof Layer

Full terrace system

Incorporating planters and planter walls into a Raaft full terrace system guarantees fast and easy installation and a trouble-free future for your roof garden or terrace.

The full terrace system uses lightweight, dimensionally stable aluminium joists to create a level, stable platform for planters, decking and tile surfaces. These are mounted on height-adjustable pedestals that allow the whole platform to be elevated to threshold level, spread the weight loadings evenly over a much larger area, and provide ample space between the deck and the roof layer for drainage.

Floor Structure Panels – a significant feature of the Raaft system – integrate easily into the terrace system and provide stable, permeable platforms for planters.

The Raaft terrace system can also be supplied with all components meeting Class A fire rating requirements for high-rise residential buildings, and to withstand uplift in locations that are exposed to higher winds.

What makes Raaft Planters Unique?

If Planters are not bolted down, they move and become misaligned. This relates to platers with enlarged footplates but requires no fixings. The panels will move and warp over time with the weight of the soil, because of this, and also due to hardier roots getting under the footplate and lifting the structure. Raaft Planter system solves this issue as they are bolted to Floor Structure Panels.

Roof Terrace Projects

For examples of how well the Raaft full terrace system works when installed over an insulated roof layer, take a look at our Tailors Corner and 116 Old Street case studies.