ᐅ Thermal bridge caused by fasteners in ETICS?

My question might seem a bit unusual for the experts here, but it doesn’t hurt to ask ;-). Here’s the situation: I want to secure a patio roof to the house wall using long screws. The wall has a 20 cm (8 inches) thick external thermal insulation composite system (ETICS) with polystyrene. The screws would pass through the wood of the patio roof, the facade, and the insulation all the way into the masonry.

My carpenter suggests using standard long screws with plastic wall plugs.

Could these screws create a thermal bridge? I’m less concerned about energy loss, as I don’t think it would be significant, but I want to make sure that no condensation forms inside the masonry.

Extensions attached to an exterior wall with external thermal insulation composite systems (ETICS) can almost only be installed in the way you described. Terrace roofs, awnings, canopies... there will be no condensation issues affecting the masonry in these cases.

You are definitely on the safe side if you build the terrace roof as a free-standing structure in front of the façade, with no direct contact (apart from the connection of the roof to the plaster).

It is not recommended to simply drill through an external thermal insulation composite system (ETICS).

At the drilling points, air pockets will form, allowing moisture to enter or even flow in. This will lead to freeze-thaw damage, and the consequences depend on the specific situation.

If you do drill through an ETICS, insulate the drilled hole with a conduit and allow the screw some movement to accommodate any settling of the attached component.

Imagine the screw is embedded in the insulation material while the balcony still shifts by 1.5cm (0.6 inches). Protect this anchoring accordingly. Make it flexible like a joint! And be meticulous in ensuring a proper moisture seal that will last over time!

It depends on how the component is fastened. The design of the contact point is important. If a suitable plastic anchor is used and installed correctly, there should be no condensation between the screw and the anchor or between the anchor and the screw. The balcony should not deflect by 1.5cm (0.6 inches) if it is constructed properly; this also includes the design and depth of the foundations to prevent such settlements. Otherwise, movements of 15mm (0.6 inches) will not only cause damage to the external thermal insulation composite system (ETICS).

For cases like this, there are also thermally broken brackets designed specifically for installation with ETICS (External Thermal Insulation Composite Systems). Search online for mounting elements -> heavy loads -> UMP aluminum Z. This cylindrical bracket does not conduct heat and is specially made for canopies, awnings, or similar structures. Installation is still possible even after the ETICS has been installed. You need to buy a hole saw and drill through the insulation foam down to the concrete, then the bracket can be fixed to the concrete with a plate at the front for screwing on the awning.

I have used them myself on my stainless steel balcony. I can only recommend them; any other solution would create thermal bridges again.

Regards