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Colorcoat Connection® FAQ’s – Side and end laps

26 July 2007 No Comment

Is there any best practice advice you can give me on how to best seal built- up side lap joints? 

Side lap joints are formed where the profiled edge of one sheet overlaps the edge of the adjacent sheet. Liner sheets are normally 0.4 mm or 0.7mm thick. The joint is sealed either using a sealant bead, which is placed inside the overlap joint, or an external tape, which is placed over the joint line on the cavity side of the liner sheet. The joint can be reinforced with stitcher screws or rivets, which is a requirement for most firewall constructions. Side lap joints account for approximately 75% of joint length in the cladding. There is approximately 1 metre of joint for every square metre of cladding; depending on the sheet cover width. For this reason, effective sealing of this joint provides the basis of an air-tight cladding system.Any edge damage to the sheet profile will affect the tightness of the overlap joint and the performance of unsealed joints will be poor and have a high degree of variability. The use of a good quality sealant tape (such as Polyband or T-foil) or an internal sealant bead will produce a good quality air-tight joint.  

Similarly, is there any best practice advice you can give me on how to seal built- up end lap joints?

End lap joints are formed where the profiled end of one sheet overlaps the end of the adjacent sheet. The minimum recommended overlap is 60 mm. Liner sheets are normally 0.4 mm or 0.7mm thick. The joint is sealed using a sealant bead, which is placed inside the overlap joint, or using an external tape, which is placed over the joint line on the cavity side of the liner sheet. The joint is reinforced with stitcher screws or rivets. Stitcher screws should be fitted in every valley to provide compression of the sealant bead. The use of a good quality sealant bead will produce a good quality air-tight joint. If the sheet is secured only in alternate valleys, the unsecured valleys can open slightly, stressing the sealant bead and compromising the performance and longevity of the joint. An external sealant tape can provide an air-tight joint, but is difficult to secure accurately around the profiles, which can lead to workmanship issues and reduced performance. Poorly laid tape can also trap internal condensation, resulting in potential corrosion of the liner sheet. (We recommend that you consult the relevant cladding system manufacturers for the recommended size and grade of sealant beads). For more information please contact the Colorcoat Connection® helpline.

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