The four criteria for assessing class importance apply to blockhouses as follows:
- Period (currency): Restricted. The tradition of building blockhouses lasted for just over 250 years, starting in 1398, most being built between 1539 and 1545, and the last in 1651.
- Rarity: Very rare. A total of 27 sites are known; although the sites of some unknown examples may be identified there is likely to be little remaining of such monuments.
- Diversity (form): Medium. The classification proposed above illustrates the diversity of this class of monument.
- Period (representativity): Medium. Blockhouses were one of a wide range of classes of similar date; there are however relatively few devoted to defence and this class is important in reflecting a major change in defensive techniques.
Assigning scores to these criteria following the system set out in the Monument Evaluation Manual, blockhouses yield a Class Importance Value of 28 out of a maximum possible score of 64, reflecting the rarity but basic homogenity of the class.