Any old adhesive residues should be removed by mechanical
methods such as scraping, shot blasting and grinding etc.
Certain underlayments such as STOPGAP 1200 PRO are able
to cope with firmly adhered and hard adhesive residues
that are not water soluble. However, for all another smoothing
compounds at least 75% of the floor area should be exposed,
followed in most instances by the application of neat STOPGAP
P131 PRIMER, allowed to dry and then the application of the
appropriate STOPGAP smoothing underlayment. Please refer to
Technical Service for product selection.
Note:
1. If in doubt remove all traces of adhesive residues back to a clean,
sound micro-textured dust free substrate.
this is a direct quote from a sub-floor prep guide.