How to Handle Joint Leakage in GRC Exterior Walls? Repair Solutions and Practical Standards

GRC facade joints are high-risk areas for leakage, mainly caused by sealant aging, improper construction, and thermal expansion/contraction deformation. Leakage not only affects the building's appearance but also erodes the internal structure, so scientific repair solutions must be adopted promptly to thoroughly resolve leakage problems. Drawing on years of leakage repair experience, Qinglong explains the core treatment methods and practical key points.

I. Diagnosis and Investigation of the Core Causes of Joint Leakage

Accurate diagnosis of the cause is the prerequisite for repair and requires a comprehensive investigation. Sealant problems: sealant aging and cracking, improper selection (e.g., insufficient movement capability), or incomplete filling during construction allow rainwater penetration. In the Sanya Yingbin Yihao project, Qinglong found that many leaks resulted from aged and failed sealant. Substrate treatment problems: incomplete cleaning of joint surfaces, with dust and oil residue present, prevents the sealant from bonding firmly, resulting in gaps. Structural deformation problems: thermal expansion/contraction of GRC components or building settlement causes joint cracking, and hyperbolic component joints in particular are prone to leakage due to deformation. Construction technique problems: insufficient joint width allowance and non-standard foam backer rod filling compromise the sealing effect.

II. Basic Repair Process and Operations for Joint Leakage

Follow standardized procedures to ensure long-lasting repair results. Cutting and cleaning: cut along the leaking joint to remove the old sealant and foam backer rod, clean surface dust, oil residue, and aged layers, and grind rough surfaces to ensure firm sealant adhesion. Substrate treatment: apply a dedicated primer to enhance adhesion between the sealant and the GRC surface, and proceed to the next step once the primer is surface-dry. Filling the backing material: select closed-cell foam backer rods with a diameter 20% larger than the joint width and fill them evenly into the joint, reserving sealant application depth (approximately 1/2 of the joint width). Sealant application: apply high-modulus silicone weather-resistant sealant evenly into the joint, ensuring complete filling without air bubbles and a smooth finished surface. Qinglong uses specialized application tools to improve sealant application precision.

III. Specialized Repair Solutions for Different Types of Joint Leakage

Customize repair strategies for different joint types. Flat panel splicing joints: repair using "foam backer rod + double-bead sealant"; the outer sealant should protrude 2-3mm above the surface to form a water barrier line and prevent direct rainwater scouring. Internal and external corner joints: prone to cracking due to stress concentration, these require additional metal trim strips combined with sealant for dual protection; the trim strips must be firmly fixed and fit tightly with the sealant. Special-shaped component joints (e.g., hyperbolic panels and hollow-out panels): use a combination of flexible sealing tape + sealant, with the tape adapted to the component profile to ensure full joint coverage. In the hyperbolic component repair at the Guangxi New Media Center, Qinglong resolved complex joint leakage with this solution. Anchor point joints: clean the gaps around anchor points, fill with sealant, then add waterproof cover plates for enhanced protection.

IV. Post-Repair Quality Testing and Preventive Measures

Combine testing and prevention to avoid leakage recurrence. Repair testing: use a water spray test to verify repair results—spray the joint area with a high-pressure water gun for 30 minutes; no water seepage on the inner side qualifies as a pass. Regular inspection: after repair, check the joint sealant condition quarterly and promptly clean surface contaminants to prevent corrosion. Preventive measures: select high-quality sealant with movement capability of ≥±25%, strictly control joint width during construction (reserving 8-12mm), and perform regular maintenance to replace aged sealant. Qinglong provides clients with joint maintenance records for early warning of leakage risks and reduced repair costs.