Compatibility Is the Whole Thing

A sealant that will not bond to one of the substrates, a coating incompatible with what is already there, or a membrane patched with a different chemistry — each of those is a competent-looking repair that fails at the interface within a year or two. Compatibility is invisible and it decides the outcome.

Manufacturers warrant their material performing as specified, under conditions they define, installed as they instruct. That is a reasonable thing to warrant and it is not the same as a warranty that your building will stay dry. Envelope failures overwhelmingly occur at transitions — roof to wall, wall to window, wall to slab edge, balcony to door — and transitions are exactly where one manufacturer's responsibility ends and another's has not begun.

So specifying by product leaves the most failure-prone parts of the building unassigned. The alternative is to treat the envelope as one continuous system and to detail every transition deliberately, verifying material compatibility rather than assuming it. Two competent products meeting at an undetailed joint is the most common failure we are called to look at, and both products performed exactly as warranted.

1. 01Identify existing materials before specifying a repair.
2. 02Use compatible products, verified rather than assumed.
3. 03Test adhesion where the existing material is unknown.
4. 04Detail transitions between systems deliberately.

Find out what is already there before specifying what goes on top. Where nobody knows, an adhesion test costs very little and prevents a repair that debonds within a year.

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