Step-by-Step Guide to Installing Ventilated Wooden Facade

When deciding to crown our building with a wooden facade, several key decisions need to be made that will impact the durability of the constructed facade walls. I believe the most important decision is the choice of the frame system and its attachment to the wall. The frame will be spaced from the wall by the thickness of the insulation and the thickness of the ventilation void. Simultaneously, it will bear the weight of the facade boards, each square meter of which weighs around 13kg (in the case of Siberian larch with a thickness of 20mm). Therefore, it’s crucial for the frame to be stable and resistant to distortions over the years because any deviation will affect the facade boards, potentially leading to their complete warping, screw tearing, or cracks around the screws/nails.

In practice, two methods dominate the attachment of the frame to the building’s wall. The first involves screwing through spacer screws directly through the insulation layer and anchoring into the building’s wall. Typically, the insulation layer is 15cm-20cm thick, and an additional 2cm expansion joint gives us an average of 19.5cm through which the screw must pass before anchoring into the wall for about 7cm. Hence, the length of potential screws would be over 26cm. There is a risk that with such a length, the screws will be prone to tearing under the weight of the boards because the entire weight of the boards and the second level of the frame will act on the screws beyond their edge. Moreover, the screw is not supported in any way in the insulation layer. Therefore, we recommend such solutions only for insulation up to 15cm thick using spacer screws with the best possible parameters.

A decidedly cheaper and more practical alternative is the installation of spacer brackets in the form of aluminum angles. On one hand, this solution guarantees stable support of the frame, even with above-average loads and thick insulation, and on the other hand, it allows for leveling the first layer of the grid, which is significantly more troublesome when using spacer screws.

The next step is to choose the material for external wall insulation. We must decide whether to insulate the building with wool or polystyrene. I will leave the discussion on this topic and summarize the differences for another blog post. However, I will compare based on the decision regarding the wooden frame mounting system. If, despite everything, we decide to use spacer screws, the choice of insulation type will not matter much. On the other hand, if we choose spacer brackets according to the suggestion of experienced Wood of Fire installers, rock wool will be a decidedly better solution. The reason is quite prosaic. We use screws after mounting the insulation, and it’s best to screw the brackets to the wall before laying the wool/polystyrene, as otherwise, we would have to cut out rectangles of the bracket base size, which would be troublesome and contribute to the creation of many thermal bridges. Rock wool can easily pass through the aluminum parts of the bracket, which are 3mm thick. Simply place the wool sheet in the designated spot, the brackets will indent on the wool, allowing for cuts in the wool at these points, and then transfer the wool through the brackets. After laying, the wool will snugly fit against the brackets on both sides and provide thermal insulation. A similar attempt with polystyrene will fail because the polystyrene sheet may break at the cut and certainly won’t snugly fit against the brackets on both sides, increasing the pressure to create thermal bridges. After transferring the wool through the brackets, we additionally anchor it to the walls.

Usually, the brackets protrude 2cm-4cm beyond the outline of the insulation. We attach a vertical batten to the brackets. The vertical batten usually has a cross-section of 30×60 or 45×70 to avoid increasing the building volume too much and to allow for the use of shorter brackets; we embed the vertical battens partially into the wool. The batten protrudes beyond the outline of the wool by 2cm-4cm, thus creating vertical air circulation. We generally recommend making the frame with wooden battens because they are better insulators, do not conduct cold like aluminum, and are simply cheaper than aluminum frames.

Next, we attach a vapor-permeable membrane in the form of a film to the vertical battens. The next step is to install horizontal battens, which should be impregnated and, in the case of boards without tongues, should be in a color similar to the board color. It’s best to use Siberian larch battens with a cross-section of 28×45. It’s important to pay close attention to the horizontal battens and choose the best possible protection for them because, after the facade board, they are the most exposed element of the facade to external factors. We space the vertical and horizontal battens in a grid every 50cm-70cm, depending on the specific layout of the wall.

The final step is to screw the Shou Sugi Ban facade boards to the constructed wooden frame. We can use nails or screws. However, it’s important to remember to use two screws/nails per board width on each horizontal batten, directly through the board.

It’s definitely best if all facade work is carried out by a qualified team of installers. In addition, when choosing the option of material delivery and comprehensive execution of works from SSZ for the entire range of work and materials, a 5-year warranty is provided, which is an additional advantage compared to conducting work independently.

As Wood of Fire, we are both producers of charred Shou Sugi Ban boards and specialists in the installation of ventilated wooden facades, allowing us to provide comprehensive service to our clients and offer the most practical and proven solutions in the field of wooden facade execution.

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