<p>Housing expenditure can reflect two distinct dynamics: affordability constraints that limit resources available for childbearing, and willingness to pay for family-oriented housing that may support childbearing. Prior research relying on property prices primarily captures affordability constraints, while the limited literature using household-level housing expenditure has only begun to address willingness-to-pay considerations. This study examines how rent and mortgage payments relate to fertility in the United Kingdom from 1992 to 2021, and how these associations vary by housing tenure and income. Using longitudinal data from the British Household Panel Survey and Understanding Society, multilevel discrete-time hazard models estimate the likelihood of first, second, and third births. Results show that higher housing costs are positively associated with first, second, and third births among owner-occupied households. Among private and social renters, housing expenditure shows no clear relationship with childbearing. Although fertility follows a clear income gradient, there is no evidence that the housing expenditure–fertility association differs across income quartiles. Interaction tests further indicate stability in these associations across historical periods. Overall, the findings suggest that household-level housing expenditure provides insight into how housing investment and fertility are jointly structured beyond what macro-level affordability indicators reveal.</p>