Repairing Exterior Wall Tile Detachment: Using Alkali Resistant Glass Fiber Mesh + Crack‑Resistant Mortar As A “Transition Layer”

After years of weathering, the old wall surface has become aged and micro‑cracked; the new repair mortar has high shrinkage and a different coefficient of thermal expansion from the old substrate. If they are brought into direct contact, concentrated stress builds up at the interface, causing rapid re‑delamination. The transition layer acts as a "soft connection": the mesh disperses the stress while the crack‑resistant mortar accommodates deformation, allowing the old and new layers to work together.

Base (bonding layer): Apply a primer on the cleaned old tile surface to ensure adhesion.

Middle (reinforcing layer): Trowel on a first coat of crack‑resistant mortar (about 3–5 mm thick), then immediately press the mesh into it. The mesh must be laid flat with overlaps of no less than 50 mm, and fully embedded in the mortar without any voids.

Top (levelling layer): After the base coat stiffens, apply a second coat of crack‑resistant mortar to cover the mesh, resulting in a total transition layer thickness of about 8–10 mm.
This construction provides both tensile strength and flexibility, effectively buffering substrate movement.

① Clean and roughen – Remove loose tiles, grind the old substrate, and eliminate dust and grease.
② Lay and fix the mesh – Cut the mesh to size, spread it over the primed wall, and press it into place with a trowel (for large areas, use small dabs of mortar to tack it).
③ Apply mortar in layers – First trowel a thin coat over the mesh, pressing the mesh into the slurry, then level to the designed thickness with a second coat. Cure properly to avoid early shrinkage cracking. Unlike self‑adhesive tapes, this mesh relies entirely on mortar encapsulation for anchorage, so each layer must be firmly compacted to keep the mesh in the middle of the mortar bed – not on the surface.
 

Ordinary fiberglass mesh becomes brittle and loses tensile strength rapidly in the alkaline environment of cement mortar. A specially coated alkali‑resistant mesh, however, resists the corrosive attack of cement hydration products, providing a service life that matches the building itself. Its uniform grid size (typically 4×4 mm or 5×5 mm) distributes stress across multiple grid cells, making it far more effective against cracking than steel mesh or plant‑fibre alternatives.