Re-adhesion of delaminated historic plasters is of paramount importance to ensure their survival. This is typically achieved with injection grouting. Although, by definition, adhesion is thus a fundamental property for grouts, when grouts undergo laboratory testing, often a thorough assessment of fresh properties is performed, as well as evaluation of some hardened properties (such as permeability and compressive strength), but the assessment of adhesion is often overlooked. In addition to this, typically, little or no attention is given to the original materials the grout is meant to stabilise, and how the grout adheres to such specific plaster(s)/support. This paper aims to critically review adhesion testing of grouts, to discuss different methodologies and procedures adopted, including laboratory and site testing, and to discuss how these can inform the choice of materials to implement on site.