Whether terrace , shed or canopy, double-wall sheets are suitable for countless areas of application around the house and garden. With our instructions, the versatile panels can be laid without any problems.

material and material properties

Ultimately, there are double-wall sheets today in countless variants and materials, but two plastics have prevailed as the most common and widespread materials:

  • polycarbonate
  • Acrylic (“Plexiglass”)

Both plastics have all the material properties that are so important for these panel materials:

  • carrying capacity and resilience
  • High resistance to weather and environmental influences
  • High toughness and impact resistance
  • Easy execution as transparent, translucent building boards


However, it is precisely these properties that make processing a double-wall sheet more difficult and define some essential requirements for a successful processing process:

To cut

Twinwall sheets sing and cut quite well from the exact plastic recipe. However, for a clean cut without fraying, crumbling edges and to avoid cracks, knocks or broken corners, you should make sure that your tool fulfills the following:

  • High speed or number of strokes
  • As vibration-free, uniform cutting movement as possible
  • Well-sharpened tools, ideally with saws with small teeth

The fewer sudden impulses on the panels during cutting, the safer you will get an optimal work result. The following power tools, for example, are well suited and can be found in almost every hobby workshop in one form or another:

  • Hand circle saws
  • table saws
  • plunge saws
  • Cut-off grinder with cutting blade for metal
  • requires saber or jigsaws


As a rule, it is completely unnecessary to drill double-walled plates for assembly. However, for other topics, such as cable bushings, it is quite easy to do. Similar requirements apply here as for cutting. Above all, a high speed and a sharp drill are important. Special plastic drills do not exist, so both metal and wood drills can be used. Wood drills have the advantage that you can use the protruding tip to start easily and precisely at the desired point. All types of drills are well suited. Cordless screwdrivers, on the other hand, should only be used with caution because of the low speed. Pillar drills can be used very well, since tilting or tipping in the drill hole is impossible.

Note: Test a few holes on a test piece in advance to get a feeling for the process in the existing material. If you drill too fast, the edge of the hole can tear. If you drill too slowly, the plastic can become soft. The drill hole runs and looks ugly.

Lay double wall panels correctly

Now that you know the basic processing methods, it’s time to actually lay the double-walled sheets. Generally speaking, the panels are very easy to install and this is one of the reasons why they are so well known and popular. With the following instructions on the main topics relating to construction and assembly, assembly is a breeze:

The substructure

Double-walled sheets are able to span a certain span in a self-supporting manner, i.e. without a substructure. Depending on the panel thickness, material and design of the webs, this dimension can vary and is specified by the manufacturer for each specific panel type. Usual spans are between about 80 and a maximum of up to 120 centimeters. This means that as a substructure for this form of roofing, a single layer of joists with a maximum spacing between the joists of the span already mentioned is sufficient. In the private sector, it is mostly wooden beams that are used as roof rafters or even supporting structures. However, metal profiles can also be easily used for the construction of double-wall sheets. It is only important that there is a surface of about 8 to 10 centimeters wide on the top side, on which the plates can be placed. In addition, fasteners must be able to be screwed into the carrier.

The fortification

In relation to their area, double-wall sheets are extremely light. In terms of substructure, this is an enormous advantage. However, this also means that you not only have to secure the panels on their substructure against slipping and shifting. The wind suction, i.e. the lifting of the panels upwards due to strong winds, must also be compensated for by a suitable fastening. It is common practice to lay the individual panels in such a way that they are always butted over the beams. This is exactly where the joints can then be fixed accordingly. There are two common variants for this:


Many manufacturers offer customized clamping systems for their panels. A lower shell is usually mounted directly on the carrier. Then the double-walled plates are placed and clamped by an upper shell with a screw connection. Tightening torques, dimensions and the necessary bearings are optimally coordinated and included. In addition, detailed assembly instructions ensure that you can hardly use these prefabricated products incorrectly.

terminal strips

Alternatively, you can also fix the double-walled sheets yourself using commercially available standard products. Here, too, it makes sense to push the panels onto the supports and fasten them exactly there.


  • Foam rubber (e.g. as self-adhesive roll goods)
  • Flachprofil Aluminium, ca. 3x50mm
  • Wood screws, approx. 6x80mm


  • Pre-drill the aluminum profile in the center of the longitudinal axis, drilling distances approx. 20 to 30 centimetres, diameter approx. 1 to 2 millimeters larger than the screw diameter
  • Provide the substructure on the upper side with foam rubber strips approx. 2 to 3 centimeters off the middle
  • Lay the boards on the substructure, arrange the joint in the middle over the beam and move the boards about 1 centimeter apart
  • Aluminum profile provided with foam rubber strips on the underside of each edge
  • Lay the aluminum profile with foam rubber on the double-walled panel
  • Guide wood screws through the holes in the aluminum profile and screw into the substructure
  • Limit the tightening torque so that the plates are not compressed
Note: The necessary fixation means that the substructure, panel and attachment ultimately have the same length. Nevertheless, it can happen that the panels protrude or recede slightly over the supports, depending on the temperature and insolation. The reason is the very high thermal expansion of the panels.


Of course, it can happen again and again that boards are not just the right size for the desired application, not only in length but also in width. Double-wall sheets can also be cut lengthwise, i.e. parallel to the webs. However, make sure to shorten the individual elements so that the overhang is evenly distributed on both sides beyond the last bar. So you can lay the plates well and also clamp them. If, on the other hand, the last bar is too far away on one side, press the plate together. As a result, it deforms, even breaks in extreme cases and can no longer be securely fixed.

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