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Preparing Green Roofs for Winter

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Careful planning of green roof maintenance is an important aspect of preserving the long-term viability of green terraces. Without rigorous maintenance, a green roof has little chance of remaining in optimal condition, both aesthetically and functionally.

Neglecting maintenance can even lead to irreversible damage to the component layers, and in more severe cases, the failure to fulfill a very important role: protecting and maintaining the waterproofing integrity. For this reason, we emphasize to all our clients the importance of following a strict maintenance plan throughout the year.

In the transitional temperate continental climate, the approach of winter brings the first persistent snow layers. Here are four essential aspects for maintaining a green roof in optimal condition during the winter months.

1. Cleaning drains and gutters

This is important throughout the year. During winter, especially when solid precipitation accumulates in large quantities, and periodic melting of snow and ice tests the waterproofing of the roofing. If the drainage system is ineffective (under-dimensioned, or after installing the green roof, other construction teams left packaging debris on the roof which was blown by the wind into the drainage areas), water will accumulate on the roof and find its way through weak points in the waterproofing, ultimately damaging vegetation that does not tolerate standing water.

To prevent these errors, for new constructions it is recommended that the last team to leave the roof be the green roof installer, minimizing the risk of other construction teams leaving foil, cardboard, or cloth debris on the green areas, which can later be blown or washed into the drains.

To keep the drainage system functioning optimally, all components must be carefully inspected and cleaned. Installing inspection boxes at each drain on the green roof is mandatory, as debris tends to accumulate around these drains, effectively blocking the water flow.

2. Snow removal

As with any roof, accumulated snow should be evenly spread. To prevent point loading on the structure, snow drifts must be redistributed. In areas where heavy snow accumulation is frequent, this should be considered during the design phase. Since there is no specialized literature on this, our recommendations are based on our own experience. When removing excess snow, a protective layer of 15–20 cm should be maintained, protecting the vegetation both mechanically and from extreme weather effects such as frost or sudden temperature changes. The simplest and most effective method is to scoop the snow onto a blanket and pull it to the roof edge or uncovered vegetated areas. Maintaining a 20 cm protective snow layer eliminates the risk of damaging the vegetation.

3. Waterproofing

In the first weeks of winter, the condition of the waterproofing layers can be checked, especially seams, corners, or any vulnerable areas exposed to mechanical stress or severe weather. Additionally, before the first snowfall, the general condition of the green roof should be inspected, including damage from wind, rain, or birds (birds often nest on ultralight roof structures, with hydrophilic mineral wool being a preferred material). Addressing any issues ensures quick recovery in spring and protects the waterproofing from extreme weather exposure.

4. Pruning and weeding

Late autumn or winter is not an ideal period for removing dead or unwanted plants, or trimming the vegetative mat. Besides maintaining a natural appearance, these plants provide additional protection for low-growing plants and dormant shoots until spring arrives.

5. Fertilizer application

With the arrival of autumn, winter-preparation fertilizers should be applied, rich in phosphorus, potassium, magnesium, and micro- and nano-elements. These fertilizers help vegetation withstand winter better and promote an earlier start in spring. The recommended dose is approximately 40 g/m².