I have a bay window with PVC double glazing. I have covered where the frame meets the ragged edges of the surrounding wall with PVC architrave mouldings (US spelling moldings), which I stuck to the surrounding walls using ~ 1 cm wide double-sided tape designed for the purpose (comes in a flat spiral, very sticky and disintegrates easily if you try to unstick it again).
The tape works fine for the mouldings at the top of the window frames. However, it's mostly intended for sticking to flat surfaces and the vertical mouldings have come free from the walls along long sections because they lie across the V-shaped join where wall meets frame (one side of the V is the vertical of the PVC frame, the other is the wall, and the moulding goes across the V to cover the messy joint at the point of the V). So the moulding and the sticky tape only touch the V at exactly two points -- i.e. if you look at the whole length of the moulding, they touch the wall/PVC along two very thin vertical lines rather than the whole back surface of the moulding.
I tried laying several strips of tape over each other to build up an angle to meet the wall/PVC.
I tried clamping the PVC moulding in place for a day or two after sticking (which I found tricky to achieve in itself...).
The old plastic in the same location that I replaced also used a very similar type of tape. Unfortunately that has gone to the dump (silly me) so I can't check the details...
What's a sensible way to firmly attach the vertical mouldings to cover the wall/PVC V-joint?