1979 flat, very loose areas of original screed exposing paper slip layer

This is work that as been done by DIY methods if you require my expertise they will need more information ne photos Regards Chris

Hi James, I wouldn’t recommend pouring self-levelling compound directly over the exposed paper slip layer or over loose and crumbling screed. From your description, it sounds like the original floor may have been constructed as an unbonded screed system, with a separating layer between the screed and structural concrete. The first step would be to assess the condition of the remaining screed. Any loose, cracked or unstable areas need to be properly investigated, as applying SLC over them could lead to further cracking or failure. Depending on the condition of the floor, the best solution may be to remove the defective screed and reinstate it using a suitable screed system before applying a compatible levelling compound. I would also recommend checking the floor construction, permissible loading and any acoustic requirements, particularly as this is a first-floor flat. Given the age of the property, any unidentified materials should be assessed before further disturbance, including an appropriate asbestos survey where necessary. A site inspection would be the best way to determine whether a local repair is possible or whether a more extensive replacement is required. Hope this helps!