While the role of women as designers and/or patrons of architecture in eighteenth-century Britain and Ireland is increasingly recognised, their role in the making of architecture remains contested. This article sheds light on the subject by drawing not just on the extensive secondary literature, but also on records of livery companies and other primary sources in London and Dublin. It begins with the building site, focusing on female apprenticeship. Here substantial evidence is provided showing that girls bound to bricklayers, carpenters and plasterers as apprentices — the so-called ’lost labourers’ of recent scholarship, recorded in guild registers and court minutes — did not in fact acquire craft skills or work as on-site operatives in those trades. The article then turns to those areas of the building process to which women did make a substantial contribution: first the practical realm, including brickmaking, lime-burning and the cleaning and preparation of carved and moulded work for painters and decorators; then the organisational realm of business, including property development, house-building and estate management. Taken together, these stories from the margins of architectural and labour histories make clear the distinction between competence in skills and competence in business, giving a more accurate picture of the multifarious nature of female participation in the construction industry in the Georgian era.