Case 1

Good Practices

Proper movement joints must be incorporated to prevent overall shrinkage of the frame and to allow expansion of the tiling.

BS EN 26 advises that the movement joints should be provided horizontally at each storey and vertically at approximately 3m centres. The joints should reach right back to the wall surface, be minimum of 6 mm width and should be pointed with an elastomeric sealant.

Cement mortar should not be used due to sealant failure in movement joints. Cement mortar is not flexible and hence not suitable for use in a movement joint. It cannot accommodate any movements of the tiling system and might lead to cracking of adjacent tiles.

The general performance of the common sealants used outdoor are shown in the table below:

Design

Select sealant joint type and mode of application in accordance with BS 6213 or SS 654; including requirements for quality management programme. Adopt the guidelines on the selection of construction sealants in accordance with BS 8221-2, SS 509 or equivalent. For grading of sealant (i.e., pourable or non-sag), refer to ASTM C920-18 (tested), ASTM C639-15 or equivalent. Make provisions for access for regular sealant inspection and avoid placing design features/services across joints that impede access for maintenance.

Construction

Apply sealants in accordance with recommended guidelines in BS 8000-0, BS 6093, SS 654 or equivalent. Perform dynamic peel test and dynamic tensile test on structural sealants in accordance with ISO 28278-2 or equivalent. Carry out non-destructive and destructive inspection procedures of weatherproofing sealant joints in accordance with ASTM C1521-19, BS EN 15651-1 or equivalent. Use a two-cloth method to properly clean and prime.

Sealant

Design

Include capping to protect sealant joint. This is to ensure no chemical reaction to take place at the joint.

Installation

Sealants should be applied to dry, non-greasy surfaces.

Avoid bridging angles, particularly with mastic strip sealants. Apply extra thickness at corners as a precaution.

Material

Sealants must be continuous and of consistent quality.