Mortar skinning occurs when the thin-set is left exposed to the air for too long, causing the surface to dry out and lose its tackiness. This dry layer acts as a barrier that prevents the tile from embedding into the mortar bed. Even if the tile appears to be stuck initially, the bond is superficial and essentially non-existent. Over time, the lack of a proper chemical and mechanical bond will lead to loose tiles, hollow sounds when walked upon, or complete detachment from the subfloor. To prevent this, installers are advised to spread only as much mortar as can be covered by tiles within the open time specified by the mortar manufacturer. Environmental factors like heat, low humidity, or drafts can shorten the open time significantly. If mortar does skin over, it should be scraped off and replaced with fresh material rather than trying to dampen or re-work the dry layer, as re-tempering will not restore the original chemical properties of the bond.
Key considerations
- mortar skinning
- tile bond failure
- thinset dry time
- thinset
- adhesive
- mortar