What type of collector carrier do I need – roof slope, collector type and surface dimensions
What type of collector support do I need – roof slope, collector type and surface dimensions
When a customer comes in saying they want solar collectors, most of the conversation revolves around the collectors themselves – their performance, surface area, brand. The support is only given attention at the end, almost as if it were just an accessory. And this is exactly the most common source of problems in practice. We have seen cases where the collector was well designed, the hydraulics were correct, but the support was unsuitable for the given roof slope, or the collector was placed at the edge of the roof without the possibility of safe installation. Result: dismantling, new costs, installation delay.
This article is intended for anyone who is considering the choice of support – whether it is installation on a sloped or flat roof, one type of collector or another, a small surface for a family house or a larger system. We will cover here the roof slope, collector dimensions, the method of embedding versus overbuilding, the number of collectors and specific products that will help you choose the right solution.
Why the choice of support is more critical than it seems
A collector support is not just a "console on the roof". It is a structural element that must transfer the load from wind, snow and the collector's own weight to the roof structure or to the load of a flat roof. At the same time, it must be dimensioned for long-term exposure to UV radiation, temperature changes (collectors commonly heat up to 100–180 °C on the surface) and humidity.
In practice, we encounter three basic scenarios of poor support selection:
- Flat roof support used on a sloped roof – the structure does not have the correct anchoring points, and movement occurs in the wind.
- Support dimensioned for a different collector size – the collector either protrudes or is not firmly secured across its entire width.
- Basic support for the first 2 collectors used without expansion – when adding another collector, the customer finds out that the original support does not support modular expansion.
Therefore, it is important to know from the very beginning: what is the slope of your roof, what type of collector you will install and how many collectors you plan now and in the future.
Roof slope – the basic parameter for choosing the type of support
The roof slope is the first thing you need to find out. We distinguish three main categories:
Flat roof and roofs with a slope up to 15°
We consider a flat roof to be one with a slope of 0° to 15°. In practice, these are most often apartment buildings, industrial buildings, and also new single-family homes with flat roofs. On such a base, you cannot simply lay the collectors flat – not only would the energy yield be poor (the optimal slope of the collector is 30–55°), but water and snow would also stand on them.
For a flat roof, you need a support that sets the collectors at the desired slope (typically 30–45°) relative to the horizontal. The support must be either anchored into the roof structure through the eaves, or ballasted (concrete blocks, gravel) to withstand wind load without damaging the waterproofing.
For a flat roof, a key parameter is whether the support allows setting the slope or is fixed at a specific angle. Products such as KS2100 – basic support for the first 2 collectors on a flat roof / slope up to 15° / 1.82 m² are specifically designed for this type of surface and are suitable for collectors with an area of 1.82 m² (type KS 2100). If you have a larger collector or a different size, you must verify compatibility – otherwise, the collector may not be sufficiently supported at the edges.
Moderately sloped roof (15°–35°)
Roofs in this slope are in a "transitional" area. A slope of 15–25° is still relatively mild, but already requires hook anchoring into the rafter structure. On such a roof, you can have a shingle, metal or tile roof – each requires a different type of hook support. Note: at a slope of up to about 25°, it is advantageous to set the collectors at a steeper angle (overbuilding above the roof) to achieve better yield in the winter period.
Steep sloped roof (35°–60°)
On a steep roof, it is an advantage that snow does not accumulate on it and that the roof slope is close to the optimal slope of the collector. Collectors are mounted parallel to the roof – they are embedded into the roofing material. For this type of mounting, it is valid that the support system must be designed as "embedding" (in-roof system), where the collector replaces part of the roofing material and is integrated into the plane of the roof.
Exactly for in-roof mounting is intended support for embedding two collectors. This system allows the basic assembly of two collectors to be anchored directly into the rafter structure so that the collector is at the level of the roof plane, without overhanging and without "bumps" above the roofing material. The advantage is lower resistance to wind load, as well as a better aesthetic result – the collector appears as an integral part of the roof.
Type of collector and its dimensions – why it matters
Mounting systems are usually designed for a specific type and size of collector. This is an aspect that customers often underestimate. In practice, there are dozens of types of flat solar collectors with different widths, heights and weights. A mounting system designed for a 2.0 × 1.0 m collector will not function properly for a 2.3 × 1.1 m collector – either the mounting points will be outside the structurally safe areas of the collector, or the collector will wobble.
Flat collector – area 1.82 m² (type KS 2100)
This collector is very common in the Central European region. With dimensions of approximately 2020 × 910 mm and an area of 1.82 m², it belongs to the category of standard flat collectors for single-family homes. A complete range of mounting systems is available for this type – from basic sets for flat roofs, through expansion mounts, up to in-roof systems.
Mounting kit for collectors on flat roofs up to a slope of 15°, for collector KS 2100F 1.82 m² is an example of a product designed precisely for this size. The kit includes all the necessary metal profiles, screws and fastenings for installation on a flat roof or a roof with a slope of up to 15°. It is therefore not suitable if you have a sloped roof with a steeper slope – a different type of mounting is required in that case.
Larger and smaller collectors
The market offers collectors in sizes of 1.5 m², 2.5 m² or even 3.0 m². The requirements for the mounting system can differ for each of them. The rule applies: always verify for which type and size of collector the mounting system is certified. If you have any doubts, contact the supplier and provide the exact model and dimensions of the collector.
Number of collectors – basic mounting system and modular expansion
One of the most important practical questions is: are you planning for only 2 collectors, or will you add more later? Most mounting systems are designed modularly – the basic set covers 1–2 collectors and additional ones can be added using an expansion.
Basic mounting system for 2 collectors
Most installations for a single-family home start with a pair of collectors. For integration into a sloped roof, the mounting system for integrating two collectors is used – a complete set that includes all components for the initial installation of two collectors integrated into the roof plane. For flat roofs, it is the mounting system for 2 collectors – flat roof, which can be ballasted or anchored into the eaves structure.
Expansion with an additional collector
If you thought ahead during the initial installation, or if the customer comes later and wants to add a third collector to an existing setup, the solution is to expand using a special mounting system. For in-roof systems, the mounting system for integrating an additional collector is intended. This component is mechanically connected to the existing basic mounting system and allows the addition of one more collector without the need to dismantle the original setup.
In practice, we recommend customers always choose a basic mounting system with the possibility of expansion – even if they are installing only 2 collectors now, it is wise to confirm that the manufacturer offers a compatible expansion module. Otherwise, it may happen that in 5 years a compatible part is no longer available and the customer will have to replace the entire mounting system.
Optimal collector area for a single-family home – how to calculate it
The size of the absorber area depends on the purpose of the system and the number of people in the household. Here are the basic reference values we use in practice:
- Domestic hot water heating (2–3 people): 2–3 m² of collector area, i.e. 1–2 collectors of the 1.82 m² format
- Domestic hot water heating (4–5 people): 3.5–5 m² of area, i.e. 2–3 collectors
- Preheating of heating (low-energy house): 5–10 m² and more, i.e. 3–6 collectors
- Swimming pool (covered 40 m²): 15–25 m² of collector area (uncovered pools require less)
From these figures, it follows that for a larger system you will certainly need a modular solution – a basic mounting system for 2 collectors + the appropriate number of expansion mounts. Therefore, it is always worth considering the total area before selecting the mounting set, to ensure that the chosen system allows the installation of all planned collectors.
Material and durability of the mounting system – what matters in practice
Mounting systems are typically made of galvanized steel, aluminum profiles, or a combination of both. Each material has its advantages and limitations.
Aluminum
Aluminum is light, resistant to corrosion and does not require surface protection. It is ideal for environments with high humidity or for roofs where weight is a limiting factor. The disadvantage is the higher price compared to steel and lower strength for the same cross-section. For steep roofs with strong wind loads, a thicker profile may be required.
Galvanized steel
Galvanized steel is significantly stronger and cheaper. Most anchoring elements, hooks and connecting brackets are made of galvanized steel. The disadvantage is the higher weight – for flat roofs this can be a limitation in terms of ceiling load capacity. If the surface is damaged (scratch, abrasion during installation), corrosion can gradually occur, so it is important to ensure the quality of the installation.
Stainless steel
Stainless steel is used mainly for screw joints and anchors in industrial applications or in environments with increased air aggressiveness (near the sea, polluted air). For standard single-family homes, the use of stainless steel at contact points is beneficial in terms of long-term reliability.
Installation requirements according to roof type – specific details
Sloped roof with tiles
On a tiled roof (concrete or fired tiles), carriers are anchored using hooks – either direct or with adjustable height. The hook is inserted under the tile and fastened with a screw into the rafter. Longitudinal rails are then mounted on the hooks, to which the collector or in-roof frame is attached. For safety, the hook must penetrate the rafter by at least 50–60 mm and the wood used must be of good quality (without knots in the anchoring area).
Important: on a tiled roof, you must consider that the tiles at the hook locations will be cut or replaced with special tiles with a groove. If this is not properly handled, water may penetrate under the roofing.
Sheet metal roof (trapezoidal sheet, standing seam)
For sheet metal roofs, there are special clamps that are fastened to the sheet grooves without drilling. This is a major advantage – the waterproofing is not damaged. A drawback is that the load capacity of such an attachment depends on the strength of the sheet metal itself and the spacing of the grooves. Heavier collectors (over 30 kg/pc) require a strength check.
Flat roof with waterproofing
Mounting on a flat roof is the most problematic scenario in terms of waterproofing. The ideal solution is ballasting – the carrier is supported by rubber pads protecting the waterproofing and loaded with concrete slabs or gravel. The weight of the ballast is dimensioned according to the wind load of the location and the building height.
If ballasting is not possible (e.g., due to floor load limitations), anchoring through the eaves or through waterproofing gaskets – sealed penetrations that maintain watertightness even in case of waterproofing failure – is used. More about this procedure can be found in the article How to properly anchor a collector carrier on a roof without damaging the waterproofing in this Knowledge Center.
Collector orientation – south, southeast or southwest
Although orientation does not directly concern the carrier, it directly affects where and how to install the carrier. A flat roof gives you the freedom to orient the carrier as you like – ideally to the south, a deviation of up to 30° to the southeast or southwest reduces output by only 5–10 %, which is acceptable. A sloped roof is less flexible in this respect – you are limited by the orientation of the roof plane.
If your roof plane is oriented to the north or deviates more than 45° from the south, we recommend not to install collectors on a sloped roof, but to consider mounting on the façade – façade mounting kits are available, which we discuss in the article Mounting solar collector attachments on a wall – procedure and most common mistakes.
A detailed comparison of the different types of surfaces can be found in the article Carrier on a flat roof vs. sloped roof vs. wall – comparison of collector mounting systems.
Choosing a carrier depending on the planned number of collectors – overview table
| Number of collectors | Roof type | Recommended carrier | Note |
|---|---|---|---|
| 2 | Sloped roof (in-roof) | Carrier for embedding two collectors | Basic set, expandable |
| 2+1 | Sloped roof (in-roof) | Carrier for embedding two + carrier for additional collector | Modular expansion without dismantling |
| 2 | Flat roof (slope 0–15°) | Carrier for 2 collectors – flat roof / KS2100 basic carrier | Ballast or anchoring must be solved |
| 1 | Flat roof | Mounting kit for KS 2100F 1.82 m² | For one collector with an area of 1.82 m² |
| 3 and more | Any | Basic carrier + required number of expansion modules | Check compatibility before installation |
Mistakes That Are Easy to Avoid
Based on experience from installation practice, we list the most common mistakes when selecting and installing carriers:
- Incorrect carrier for the type of roofing: Hooks for fired tiles do not work on concrete tiles of a different profile – the groove profile must match.
- Insufficient ballast on a flat roof: Normal wind load on the 4th floor above ground can correspond to a load of 60–80 kg on the entire carrier system. An insufficiently loaded carrier can tip over in strong winds.
- Installation without foam sealing strips: A protective gasket must be placed between the collector and the carrier strip; otherwise, contact between metal and the collector frame can occur, which causes squeaking and gradual loosening due to thermal expansion.
- Ignoring expansion: A solar collector heats up and cools down during operation by up to 150 °C. Screws must be tightened to the specified torque, not just "tightly" – otherwise, the collector can deform the strips.
- Installation without checking the load-bearing capacity of rafters: Each collector weighs 25–45 kg, so 4 collectors add 100–180 kg. Old rafters in poor condition may not be able to support this.
For more information on common problems and their solutions, see the article Common Problems with Solar Collector Mounting – Loosening, Corrosion, Leaks at Joints.
Practical Scenarios from Practice
Scenario 1 – Single-family house, sloped roof, 2 collectors: The customer has a house from 2005 with fired tiles and a roof slope of 38°, orientation southwest. They want to heat TÚV for 4 people. Solution: in-roof system with a carrier for 2 collectors KS 2100, the slope is suitable for integration. Area 2 × 1.82 = 3.64 m² is sufficient. We recommended checking the condition of the rafters, as the house is older.
Scenario 2 – Apartment building, flat roof, 6 collectors for a swimming pool: The building manager wants to supply a covered swimming pool (25 m²). Required area is approximately 18–20 m², i.e., 10–11 collectors. The roof is flat, waterproofing from 2015. Solution: a carrier system on a flat roof with ballast, divided into two rows of 5 collectors each. Emphasis on load distribution in terms of floor load-bearing capacity (a structural assessment is mandatory). For the first 2 collectors, a basic carrier for a flat roof was used, and further rows were extended.
Scenario 3 – New construction, flat green roof, slope 3°: The developer wants solar collectors on a green roof layer. Fastening through the waterproofing is not possible. Solution: special elevated carriers with integrated ballast, mounted on protective rubber pads above the vegetation layer. Concrete ballast elements were placed so as not to exceed 150 kg/m² at any one point on the load-bearing slab.
Most Frequently Asked Questions (FAQ)
Can I use the same carrier for different types of collectors?
Not always. Carriers are dimensioned for specific dimensions and weights of collectors. If you want to use a different collector than the one the carrier was designed for, you must verify that the mounting points are at the same spacing and that the carrier can support the weight of the new collector. Some systems have adjustable mounting clamps that cover multiple dimensions – this should be stated by the manufacturer in the documentation.
What slope is ideal for collectors under Slovak conditions?
For year-round TÚV heating, an optimal slope is 35–45° from the horizontal. For seasonal use (spring – summer – autumn), even 25–35° is sufficient. In winter, when the sun is low on the horizon, steeper slopes of 50–60° are more advantageous. On a flat roof, you can set the desired slope with the carrier independently of the slope of the roof itself – this is one of the advantages of mounting on a flat roof compared to a sloped roof.
Is a building permit required for the installation of collectors and carriers?
On single-family houses in Slovakia, a building notice (not a permit) is usually sufficient if the collectors do not exceed the roofline by more than 0.5 m and if it is not in a heritage zone. In a heritage zone or for a larger installation (e.g., an apartment building), a building permit is required. In each specific case, we recommend consulting with the local building authority.
How many collectors can I connect to one circuit?
This depends on the hydraulic design, not the carrier. From the carrier's perspective, the limiting factor is usually the static load on the roof and the load-bearing capacity of the anchoring elements. From a hydraulic perspective, it is common to connect 2–4 collectors in series or in a parallel-series combination in one circuit. With a larger number of collectors, it is necessary to use multiple circuits. The topic of system expansion is discussed in detail in the article Expanding a Solar System – How to Add Another Collector to an Existing Carrier.
Do I need to call in a structural engineer for the installation of a carrier?
For a standard installation of 2–4 collectors on a single-family house with a standard rafter structure, a structural assessment is usually not mandatory, but we recommend checking the condition of the rafters. For a flat roof of an apartment building, a green roof, or a larger number of collectors (more than 6–8 units), a structural assessment is strongly recommended and in many cases required by the insurance company.
What if my roof is neither flat nor steep – it has a slope of 18°, what now?
A slope of 18° is a "gray zone." Technically, it is a roof with a slope below 20°, where carrier systems for flat roofs (up to 15°) can still be used with modifications. However, at a slope of 18°, it is more advantageous to use an on-roof system for sloped roofs, where hooks are anchored into the rafters and the collectors are attached to the strips. The energy yield at this slope will be good if the roof orientation is at least close to south. In this case, we recommend consultation – contact us with the parameters of your roof.
Conclusion – How to Proceed with Carrier Selection
Selecting the correct carrier for solar collectors is not complicated if you proceed systematically. Find out the slope of the roof, the type of roofing, the orientation of the roof, and the planned number of collectors. Based on these four parameters, you can narrow down the selection to a few suitable products. Check the compatibility with a specific type of collector and make sure that the selected carrier system is modularly expandable if you plan to add more collectors in the future.
For sloped roofs with tiles or metal roofing with a greater slope, choose an in-roof system – carrier for embedding two collectors is a proven solution for the first pair, with the possibility of expansion using carrier for embedding an additional collector. For flat roofs and roofs with a slope of up to 15°, it is worth considering carrier for 2 collectors on a flat roof or KS2100 basic carrier with appropriate mounting kits.
The entire category of available carriers and mounting systems can be found clearly on the page collector mounting. If you have an atypical roof or cannot fit your situation into any of the standard scenarios, describe your case to us – slope of the roof, type of roofing, planned number and type of collectors – and we will suggest a specific solution.
Do you have a question about this topic?
Having trouble deciding or dealing with a specific situation in your home? Write to us – we are happy to help.