FAQs — Frequently Asked Questions
Here are the most common — and uncommon — questions we have been asked about Kaatop:
Can people walk on Kaatop tiles? Once the system is planted and operating, can it support someone walking on it?
The tiles were tested by IPT and withstand foot traffic for maintenance, with a concentrated load of up to 120 kgf/m² at the least favorable point (the center of the tile), meeting the ABNT NBR 15575-5:2013 performance standard.
How do I maintain the plants and harvest them?
The above-ground parts of the plants can be maintained — including pruning, foliar spraying, and harvesting flowers, fruit, and grain — just as they would be in soil or conventional hydroponics. Work on a roof is work at height and is regulated in Brazil by NR35, the Ministry of Labor’s workplace safety regulation. When installed according to the technical guidance, Kaatop withstands foot traffic for maintenance with a maximum concentrated load of 120 kgf/m².
Could the system encourage mosquitoes, including dengue-carrying mosquitoes and other species?
The risk of mosquitoes breeding is ZERO: nowhere in the system can insects reach standing water to lay eggs. The system is closed, with water circulating continuously.
Do planting, maintenance, and harvesting require specialist labor?
Plant care is essentially the same as conventional gardening, except that safety equipment — a lifeline and safety harness — is required. Roof work is work at height and is regulated in Brazil by NR35, the Ministry of Labor’s workplace safety regulation.
Does the system need cleaning or oversight by health authorities?
When the system is planted, the tiles and growing system do not need washing or sanitizing, nor is oversight by health authorities required, because the system does not produce chemical or biological agents that could harm public health.
If you choose to remove the vegetation and use the benefits of a reflective white roof, cleaning dust and stains from leaves and growing medium can improve the system’s thermal performance.
I do not want to spend time tending plants on the roof. Is that possible?
If you do not want frequent maintenance, grow perennial species that do not need pruning. Fertilization is managed by controlling nutrient levels in a water reservoir located in a service area below the roof; this can be monitored online.
If no slab or waterproofed structure is needed, how are the tiles supported and fastened? If I replace an entire roof, what holds the hydroponic tiles in place?
The support can be built as for a conventional roof. The tiles are screwed to a wooden or metal frame, as conventional insulated sandwich panels are. Side and front joints overlap. Supports must be no more than 500 mm apart (three supports per tile).
Can Kaatop be used on a wall as a vertical garden? How are the planting openings used vertically, and how large are they?
Kaatop can take seedlings grown in size 11 pots. The planting openings are 8 cm in diameter. For smaller pots or seeds, fill the openings with rockwool cubes.
How can the nutrient solution’s electrical conductivity and pH be maintained when rain falls on the roof? Will rain dilute the hydroponic solution?
Planting in these tiles really is easier than it may seem. The product is designed to keep rainwater separate from hydroponic water. Almost no rainwater enters the internal circulation system, so rain does not significantly change the nutrient solution’s quality.
Can rainwater be collected in a cistern from a roof covered with Kaatop?
Hydroponic water and rainwater are collected separately, so they do not mix. A gutter is required to collect and recirculate the hydroponic water inside the system. You can add another gutter to collect the rainwater that runs cleanly over the system’s outer cover tile.
Can Kaatop absorb stormwater runoff like a conventional green roof?
Yes, but it absorbs only 10 liters/m². To keep the system lightweight and save water, the growing medium is enclosed between the tiles in a sandwich structure, so it absorbs little rainwater. Rainwater can instead be collected and stored in a cistern by installing a second gutter to keep it separate from the hydroponic or fertigation water.
Do you recommend covering the entire roof or just part of it?
We recommend covering the entire roof for the best thermal performance. The system can also be used in strips or according to a specific architectural or landscape design.
Another option is to install the hydroponic panels like photovoltaic solar panels, on an inclined support frame positioned for the best sunlight exposure.
How should I compare Kaatop’s cost with that of a conventional green roof?
Kaatop combines three construction components in one product: (1) a watertight roof covering, (2) thermal insulation, and (3) a green roof. To calculate the cost of a traditional green roof, include (1) a supporting slab or roof, (2) root-resistant waterproofing, (3) drainage, (4) a filter, and (5) growing medium.
What growing medium should I use in a Kaatop tile? Can I use ordinary soil, or is a special hydroponic material needed?
Kaatop can be planted with any type of growing medium, provided you consider the properties of that material and the needs of the species you want to grow:
1. Conventional prepared soils and growing media, organic compost, and potting soil for containers and planters. Because these materials are loose, place a little coconut fiber or a similar material at the ends of the tile channels to prevent soil from washing out after filling (maximum soil volume: 10 liters per tile). You can also add a little water-absorbing landscaping gel to improve water retention and reduce irrigation needs. Conventional media provide a more stable, resilient system that depends less on strict irrigation control. Fertilization can still be done with liquid products applied to the irrigation channels. This is suitable for extensive green roofs with hardy, low-maintenance plants.
2. Inert hydroponic materials such as rockwool or PU foams. In this case the system works as a true hydroponic system and needs proper irrigation control (for continuous-film systems, irrigation can run for 15 minutes every hour during daylight) and nutrient management. This can produce impressive growth and harvests.
How do I plant? How do I prepare the planting openings and place seedlings or seeds in a Kaatop tile?
Planting with seedlings from pots, containers, or bags: For bagged seedlings, standard trays of 12 to 15 seedlings, or size 7 pots, wrap the seedling’s own growing medium in a little coconut fiber or another fibrous material to support the roots, then place each seedling in a planting opening (there are 20 planting positions per tile).
Planting with tray seedlings or seeds: When using small tray-grown seedlings with little growing medium, or sowing seeds directly in the Kaatop tile’s planting openings, use a more structured material such as rockwool or another medium to protect and hold the roots. Alternatively, fill the irrigation channels completely and close the outlet with a fibrous material to prevent erosion. Together with the irrigation system, this keeps seeds and seedlings stable and moist during the critical rooting stage.
How are nutrients supplied? Must I use a conventional chemical hydroponic system, or can I use organic inputs?
Nutrients can be supplied through the irrigation water, a method called fertigation. You can use a highly controlled conventional hydroponic system or liquid organic biofertilizers for simpler crop management.
What is the difference between the complete Kaatop sandwich and the half-sandwich option?
We offer two Kaatop configurations:
1. Complete Kaatop sandwich: a watertight assembly with two metal tiles and an EPS irrigation circuit panel. It is screwed directly to a wooden or metal structure at slopes from 6° to 90° (vertical).
2. Kaatop half-sandwich: a retrofit option for existing metal roofs and cladding. It includes one metal outer cover tile with planting openings and an EPS irrigation circuit panel. It does not include the base tile, so it can be screwed over the metal tiles already on site, with or without an adapter to match the existing tile profile.
Are the tiles factory painted? Is the finish powder coated?
Yes. The standard Kaatop assembly has a reflective white powder-coated finish on its outer faces. Other colors are available; contact us to check options and prices.