Yes in thinset Can youTaGNujJo apply overCan it beYou follow? The decision of whether to install a new tile installation over an existing one depends on the project, how much time you have and just how much preparation you want or need.
Surface Preparation is Key
New thinset should not be applied anywhere before the proper prep work of existing layer. This means smoothing and leveling the old thinset. An uneven surface can create problems like the new layer not holding or tiles cracking. A floor grinder can smooth out imperfections and provide an even surface for new thinset application12.
Problems with Layering Thinset
Reapplying new thinset over the old is viable in a technical sense, it just comes with its risks:
Difficulty with Adhesion: since old thinset will be rough and the new one fresh, it is challenging for them to have similar texture which could result against bond strengthening between your tiles over time you install.
Topographic Differential: When new layers are added, the existing areas become a coarser version of what is observed which can lead to trips in extreme cases or appearance-based problems14.thinset (ad)
Surface Imperfections: Other irregularities on the old thinset layer will be carried through to new concrete, making a finish uneven and less robust5.
Applications Best Practices
If you decide to go ahead and layer thinset, follow these best practices:
Ensure optimal bonding by inspecting the old thinset for any cracks, chips or other defects that should be repaired before application of new material.
Use a Primer: If necessary prime for increased adhesion between layers.
Skim Coat — Sometimes adding a skim coat of thinset can help improve the bondability of the new layer26.
Ultimately, the decision to cover old thinset is up to you but be aware of these precautions and risks so that your new tile installation will withstand time without unsightly physical results.