A large landfill for incinerated organic waste is under construction at Ragn-Sell’s waste handling and deposition plant Högbytorp, northwest of Stockholm. Here, older stabilized ash forms the base of additional waste to be filled over it. The two will be separated by a clay liner for delaying and minimizing inflow and percolation of the older waste fill. The design principle and construction of the liner are described in the paper. The clay liner is made of expanding clay with relatively high water content and a large span of particle size. The construction technique was originally planned for the forthcoming “near-surface” repository for low-level radioactive waste in Lithuania with the aim of providing very good tightness of liners at low cost.