Quick answer
Match the product to the crack. Fine non-structural cracks in concrete are sealed by gravity-feeding the low-viscosity epoxy Sikadur-20 Crack Seal into a vee-notched crack (up to 10 mm wide). Broken or spalled concrete is rebuilt with Sikadur-31 CF Slow epoxy mortar. Cracks that open and close with temperature are joints, so they need a flexible sealant such as Sikaflex Construction or Sikacryl-110. Hairline plaster cracks are filled and smoothed with SikaWall-720 E skim coat. Wide, growing or diagonal cracks in beams and columns need a structural engineer.
Common causes
- Shrinkage of plaster and concrete as they dry
- Temperature movement between different materials (brick and concrete, roof and wall)
- Settlement of foundations
- Corroding steel bars pushing the concrete off (spalling)
Step-by-step
- 1
Diagnose the crack
Hairline plaster crack, a fixed concrete crack, a moving joint, or a structural crack? Structural or growing cracks need an engineer before any repair.
- 2
Prepare
Open the crack into a small V, remove dust and loose material, and keep it dry for epoxy products.
- 3
Seal concrete cracks
Gravity-feed Sikadur-20 Crack Seal into the V-notched crack until it is full (maximum crack width 10 mm).
- 4
Rebuild damaged concrete
Apply Sikadur-31 CF Slow (about 1.9 kg/m² per mm of thickness, up to 30 mm per layer) to spalled or broken areas.
- 5
Seal moving joints
Fill joints that move with Sikaflex Construction (polyurethane) or, indoors and for painting over, Sikacryl-110 acrylic sealant.
- 6
Finish plaster cracks
Fill and smooth hairline plaster cracks with SikaWall-720 E (0.5–1.0 mm per coat) before painting.
Always follow the current Sika Pakistan product datasheet for surface preparation, temperatures and curing.
Products for this job
Sikadur-20 Crack SealLow-viscosity epoxy for sealing non-structural concrete cracks.From Rs. 3,995
Sikadur-31 CF SlowThixotropic epoxy repair mortar for hot and tropical conditions.From Rs. 3,400
Sikaflex ConstructionPolyurethane sealant for joints that move.From Rs. 4,000
Sikacryl-110Paintable acrylic sealant for interior gaps and joints.From Rs. 1,100
SikaWall-720 EReady-to-use skim coat to fill hairline cracks before paint.From Rs. 999
SikaGrout-114 PKNon-shrink grout for filling voids and base plates.From Rs. 2,999
Frequently asked questions
What is the best filler for wall cracks?
For hairline cracks in plaster, a skim coat such as SikaWall-720 E. For cracks that keep reopening, a flexible paintable sealant such as Sikacryl-110. For cracks in concrete, an epoxy such as Sikadur-20 Crack Seal.
Can epoxy fix structural cracks?
Epoxy repair products restore concrete and seal cracks, but wide, diagonal or growing cracks in beams, columns and slabs must be assessed by a structural engineer first — the cause has to be fixed, not just the crack.
Deewar ke cracks kaise bharein?
Baal jaise patle cracks ke liye SikaWall-720 E skim coat, baar baar khulne wale cracks ke liye Sikacryl-110 ya Sikaflex sealant, aur concrete ke cracks ke liye Sikadur-20 Crack Seal epoxy istemal karein.