Filling in a chased hole after electrician only did half the job

[Rod Hunter]

Hi. Please help me keep whatever hair I have left!

An electrician left half the wall unfilled and I've been trying to fill it. I've used Wickes pre-mixed plaster and pollyfilla, but the electrician put some kind of concrete-type filler in some places, which won't smooth down. Every time I fill over it and sand it back, I'm back to square one, only I'd swear his filler is getting rougher and more pot-marked all the time. What am I doing wrong please?

RH

 

[Ian]

The grey filler just looks like deep filler, rather than concrete - it's used to fill the deep channels and dry in a reasonable timeframe. I'd sand it back using a powered sander of some sort using 80 grit (especially the bit in that last photo), then use a fine finishing filler on it - something like this. Just be sure you fix that poorly filled part in the last photo first, your pollyfilla should be fine for that (but let it dry).

Gyproc Easifiller Finish Filler

Extra fine surface filler for skimming over large areas.Quickly covers large areas of light surface damage.Easy to apply and spread.Needs minimal sanding.

www.toolstation.com

You'll need to use a decent, clean filler tool. Then once this has dried, use some 240 grit sandpaper to get a good finish (maybe some even finer, if you want).