Frequently Asked Questions

How much does a vegetation blanket weigh and how much does a roof with vegetation blankets weigh?
A Sempergreen vegetation blanket weighs between 0.5-1.0 lbs per square foot (10 to 20 kg per m²) depending on the moisture content of the blanket. Tthis is without all the roof layers such as substrate, drainage layers etc.

What do vegetation blankets and other Sempervirens products cost?
If you want to receive information about what it costs to install a Sempergreen Vegetative Blanket Roof system, please get in touch by fill in the 'call-me-back form'. We will answer your requests within one business day.

Is it possible to cover any roof with a roof garden (using vegetation blankets)?
If the roof surface is waterproof and roots cannot penetrate it, vegetation blankets can be applied to the roof.

How long can you keep the vegetation blanket rolled up?
That depends on the temperature. Normaly 24 hours is the maximum. If the temperature is 25°C or more we advice you to install the blankets as soon as possible.

How many square metres of vegetation blanket fit on a single pallet?
A single pallet can hold approximately 550 square feet (50 m²).

What is the maximum slope angle for constructing a roof garden?
Vegetation blankets can be applied to slopes of up to 85°. We have developed various systems that are applicable for different construction situations. Each system is suitable for a particular type of roof.

What sort of maintenance does a garden roof with vegetation blankets require?
A garden roof with vegetation blankets is a low-maintenance system. Once or twice per year the roof should be inspected to check whether there are no undesired plants growing, which is unlikely due to the 85-95% coverage the roof offers once installed. Furthermore, drainage has to be checked for blockage because there must not be any still-standing water on the roof.

Does a roof garden with vegetation blankets require fertilization?
If a substantial extensive garden roof substrate (soil mix) was laid under the vegetation blankets, this may not be necessary. In some case however, it may be needed. Our advice is to fertilize one time per year, in the spring if one is looking for lots of blooms and the roof is visual (to be seen by people) vs. functional (mostly on tall roofs that never see visitors).

Can you construct a roof garden with vegetation blankets throughout the year?
Yes, except for when it is freezing. This is because the vegetation blankets cannot be rolled up.

How is the transport organized from the Sempergreen products?

It is possible to organise the transport by yourself, but it is also possible that we organise the transport. We can do that for whole North America. Please contact us for the transport rates.

What is the average delivery time from the blankets?

If we have the products in stock the delivery time would be 1 week.

What to do again birds and other pests?

Normaly this is not a problem. But in some periods birds can do damage. If this is a big group of birds for a longer term it will be a problem. Please contact us if you see that and we will find a solution for this. There are some environmental- and animalfriendly products to keep the birds on distance. (www.pireco.nl)