A sealant product picked on price alone can fail within a year or two if its movement capability does not match the joint it is used in -- movement class and elastic recovery, both stated on the technical data sheet, matter more than brand name.
Why this matters
A failed external sealant joint is a common and preventable route for water ingress into a care home building, often showing up later as an internal damp patch or mould report rather than being caught at the joint itself.
What to do
- 1For facade and masonry movement joints, specify a sealant tested to EN 15651-1 with a stated movement class -- for example Sikaflex Construction Purform is rated Class F EXT-INT CC 25 LM, meaning it accommodates plus or minus 25 percent joint movement.
- 2Check elastic recovery as well as movement capability -- a sealant with high movement capability but low elastic recovery (below roughly 70-80 percent) will not fully close back up after each movement cycle and degrades faster in practice than the movement figure alone suggests.
- 3Match the sealant to the substrate and service temperature range stated on its data sheet -- a general-purpose sealant rated for a narrower temperature band than the exposed elevation experiences will fail early regardless of correct installation.
- 4Reseal on a planned cycle rather than waiting for visible failure -- most polyurethane facade sealants are rated for a 20-25 year design life when correctly installed, but this assumes routine visual inspection, not a run-to-failure approach.
Primary source
Sika -- Sikaflex Construction Purform Technical Data Sheet
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