A form of fortified farmhouse, usually fairly roughly built, rectangular and 15th and 16th century in date (Mainly late 16th century and some continued to be built well into the 17th century) and generally confined to the Northern counties, only occasionally with any active defensive features (such as gun ports). The foundations and scant remains of ruins can be very difficult to differentiate from Pele Towers. Bastles were often grouped and are sometimes said placed to be of some strategic value in defending against Scottish raids. Philip Dixon made the point that the term Bastle House probably original most often referred to a higher status rectangular form of 16th century pele tower such as Hepburn Bastle whereas the cruder farmhouses were more often called Pelehouses - but because However, probably to try to avoid confusion with similar names describing different forms the Scottish Royal Commission previous distinction between 'bastle-house' and 'pelehouse' has not been widely adopted and is not now used by RCAHMS. A few very similar type buildings exist in southern Pembrokeshire and have a similar function against pirates, as would some Cornish Bartons. (Barbary pirates from North Africa were active in Southern English waters in the 15th to 17th centuries and often raided inland kidnapping individuals for slavery or later ransom. Irish pirates were active in the Irish Sea from at least the 3rd century onwards).

Bastles do often occur in small groups. In this list I have tried to record all freestanding bastles as seperate sites but pairs of bastles that share a wall (usually the short end wall) are recorded in one record as though they were one extended building. In practice these were probably not extensions of an existing bastle to add more room to the original but a new home built, probably for a family member, in a way that reduced some cost.