Old holes in concrete wall, how to fill up?

[Craftboy]

I had my bedroom wallpapered some time ago. The painter who did it filled in old holes above the window where the roller blind and curtain rods used to be. Now I was going to put up the roller blind again after the job was done, but ran into problems. There are lots of old holes behind the new wallpaper, and I can't get the plug to hold properly.

I therefore need to fill the cavity as best as possible without tearing off any wallpaper. I have drilled two holes about 2 cm apart but the wall is so porous and drilled out that there is nothing at all to attach to (see picture). In the 2cm gap between the holes, it is completely empty.

I'm considering removing the gap between the holes and then trying to fill in as best as I can. I guess I need some kind of filler, and with a "syringe" to reach as much as possible. Do you have any tips on material or alternative methods?

 

[Mikael_E1]

I would personally use either anchor compound and a proper plug or alternatively construction silicone and plug. I don't think the idea of making a larger hole solves your problem, but only worsens it.

 

[Craftboy]

I just thought it would be easier to access and fill in if I have a larger hole?

 

[Mikael_E1]

Anchor adhesive and construction silicone are sold in tubes, so there shouldn't be any problems. Just insert the plug before it hardens, otherwise it might be a bit difficult

 

[Mats]

Anchoring adhesive sounds good to me too. Just make sure to get the holes reasonably clean first (a straw and a little gentle blowing works, if you blow too hard you'll have to wash your face afterward)