Applying Polyfilla over caulk

millsy

I had an electrician move a light switch for me. That meant cutting out holes in the plasterboard to fish the cable around to the new location. I had expected him to fill the holes with something like Polyfilla. Whatever he used had a whiter finish than Polyfilla (which is more light grey). So I'm thinking maybe he used caulk. 

The caulk (which I assume it is) is not hardening like Polyfilla does. I was able to sand it to get a smooth finish but it's still a bit squishy if I press on it. Not sure if it's a good idea to leave it there and paint over it. 

Also in one area he didn't use enough filler so I topped it off with Polyfilla. However the Pilyfilla isn't hardening even though it's been applied now for about 1 week. I wonder if there is some kind of chemical reaction between the caulk and the Polyfilla where the caulk is preventing the Polyfilla from hardening. 

I'm wondering if I should just scrape all of the caulk out and apply Polyfilla to the whole lot. 

10-10-20

It sounds like low density/lightweight one-strike filler. It's slightly spongy as it remains flexible after hardening. It's designed to sit in place without sagging once applied in one go, meaning that you're not doing partial fills and can get a reasonable finish.

A better finish would be by using plasterboard joint filler as it cures harder than lightweight filler can dry.