I put down a layer of self levelling compound but have since measured and realised my floors are out of level. To rectify this I need to bring the floor level up. Some of this can be done using a modified bonded screed (over 15mm), and some will need additional self-leveller (under 15mm). My question is how do I ensure the new screed and self leveller bonds with my existing self leveller that is already laid down? I don’t have the kind of money to hire a proper scabbler which I’m guessing would be the correct thing to do? I have sanded it down but I’m not convinced this has made a difference. I do have an SDS max breaker at my disposal so one option is to try and dig out the existing leveller, but I’m trying to find a solution that doesn’t need me to do that as it will be a lot of work! Any advice?