ᐅ Are perimeter insulation boards in the ground area typically glued or fixed with mechanical fasteners (such as anchors or plugs)?

We have an extension. The construction company installed long perimeter insulation boards (approximately 2700 by 1000 mm (106 by 39 inches)) vertically on the exterior basement wall below ground level and fastened them with just one anchor at the top. In some places, they foam-sealed the joints.

Is this common practice? The remaining exterior basement walls (existing building) still need insulation. For these, smaller boards with a stepped tongue-and-groove profile would likely be considered. These boards are usually installed horizontally. Should these boards (for example, Perimeter B-3000 EPS 035 PW with dimensions 1250 by 625 mm (49 by 25 inches)) be glued? The wall will receive a new bituminous coating beforehand.

Nowadays, instead of doweling, adhesive is used, and if the gaps are too large, expanding foam is applied. Of course, only to a certain extent, but please show a picture.

Adhesion is applied if the substrate allows it. If unsure, first glue, then perform a pull-off test, and if necessary, additionally use anchors.

Fully covering the surface or only spotwise (just enough to support the main part). The insulation material itself does not prevent water from passing through. That should be the job of the thick waterproof coating (in my case WeberSuperflex 10 2k).

I have studied this topic very thoroughly.

Manufacturers specify a full-surface adhesive application depending on the load situation (e.g., groundwater). However, in practice, this is handled very differently. Since building sites often do not follow the manufacturer’s guidelines exactly, you can find all kinds of variations. Generally, these do not cause any problems.

You can also fix the perimeter insulation using only mechanical fasteners, without adhesive or bitumen. The soil pressure presses it into place firmly enough that water will never flow behind it, as long as there is no standing water or groundwater present.

Personally, I recommend spot-adhesive application in addition to mechanical fasteners. This way, you are on the safe side, and the extra effort is absolutely reasonable.

There are many other areas in construction where mistakes are actually made. How the perimeter insulation is fixed is, to put it mildly, quite unimportant.

netzplan schrieb:

Full-surface or only spot application (just enough to support the main structure). The insulation itself does not prevent water penetration. That’s the job of the thick waterproof coating (in my case WeberSuperflex 10 2k).

For this purpose, new constructions usually have a “white tank” (waterproof concrete structure), which is at least 20cm (8 inches) thick and absolutely watertight as well as vapor-tight. The bitumen coating is just an extra safety measure in case there were any mistakes during the concrete work.