Graduation of Dirk Jansen

Land subsidence related damage to residential real estate and cost effective adaptation strategies

• Professor of graduation: Prof. dr. ir. M. Kok

• Supervisors: Dr. T.S. van den Bremer (TU Delft), Dr. Z.J. Taylor (TU Delft & RED&BLUE), Dr. S. Phlippen (ABN AMRO)

Land subsidence poses significant damage risks to residential real estate, including pile rot, differential settlements, pluvial flood risk, and dewatering risk amounting tens of thousands of euros. In the Netherlands, the number of affected houses has surpassed one million and is estimated to reach two million, accounting for a quarter of all houses in the country. Without an action perspective homeowners are left to their own devices which this research shows can lead to postponing action until risks materialize. To mitigate these risks, multiple adaptation strategies are available. This thesis focuses on determining the cost-effectiveness of two general pathways for residential real estate constructed with either a wooden pile foundation or a shallow foundation: renovating existing houses or replacing them entirely. The study also investigates whether incorporating additional measures aimed at improving overall benefits such as increasing the amount of living space or transitioning towards a more sustainable house with energy label A, is cost-effective. Through a comprehensive analysis, this research provides valuable insights into economically viable approaches for addressing land subsidence-related risks in residential real estate in relation to the location specific characteristics. It proves additional measures are required to make either renovation or replacement a cost-effective adaption strategy. Two options are shown to be cost-effective. Firstly, renovation including additional investments to increase square meters of living space and transitioning to an energy performance A-label. Secondly, replacement including densification by building back more square meters of living space, increasing the amount of houses or a combination of the two. Both require large investments resembling around 75% to 150% of the current housing price respectively. Increasing the amount of square meters even further improves the result however this increasingly affects the character of the neighbourhood and its social composition. With these results, this thesis hence provides an action perspective to homeowners and stakeholders including policy makers and financial institutions.