Perimeter insulation on the front side of the floor slab

Hello everyone,

I would like to install the perimeter insulation on the front face of our new building without a basement after the base waterproofing has been done by a company.
Only weeks later did I notice that the base waterproofing makes a kind of kink at half height:



Now the question is: how do I best attach the insulation? Should I use 2 cm thicker insulation in the lower area? Should I use foam and apply thicker foam in the lower area?

Best regards

Perhaps first clarify why the bend occurred. Is the wall not flush with the base slab, and therefore a cove or similar was formed there? Normally, it is not possible to create a 2 to 2.5 cm offset with sealing slurry.

Otherwise, the cleanest way would be to first install a layer of 2 cm thick boards made of XPS or EPS with base approval in the upper area, and ensure that they close the projection as flush as possible (preferably also cut them diagonally at the bottom so that they follow the bend angle). Then install on top another layer of boards to the corresponding thickness as you want it in the end, continuously, and make sure that the vertical joints of the lower layer never lie directly under the joints of the upper layer.

That sounds like an easily implementable solution to me as a layperson. Can I use the same adhesive for bonding XPS to XPS that I use for XPS to bitumen?

If the adhesive is approved for both, then yes. However, you will usually need to consult the manufacturer, as it will not be a standard application case. It would certainly be sensible, as for the second layer both the insulation board (above the fold) and bitumen (below the fold) will be present as contact surfaces. Especially if you use XPS for the first layer, you need to see to what extent a ribbed version is available in this thickness. It is definitely advisable to bond the second layer over the entire area and, if possible, also dowel it, but opinions differ as to whether the advantages outweigh the disadvantages (damage to the building protection). What does the area above the plinth look like currently? Is a plinth profile & facade insulation already installed? If yes, also think about the joint sealing/compression tape at the boards at the joint to the profile lower edge. And for the second layer, you should bevel the boards at the bottom. This is sometimes forgotten, but is not good in the long run.