Within the castle grounds, two other historic buildings still stand – the bath-house and ice house – both of which are late 17th or early 18th century listed structures. The Grade II-listed flint-built bath-house is located over a spring that feeds into the River Darent. The bath-house was allegedly used as target practice by troops stationed at Lullingstone during the Second World War, but since losing its roof has undergone significant deterioration. The bath-house was also reputed to have been used regularly by Queen Anne, who resided at Lullingstone for some time, in an attempt to treat her purpurea (a kidney problem).
The bath-house remains an impressive structure, but has been unstable and at risk for further collapse for some time. A condition survey was commissioned early on in 2019 and confirmed this risk, which was greatly increased when a storm brought down the adjacent tree and further destabilised the structure. Emergency works to stabilise the bank and foundations took place late in 2021 to prevent the imminent risk of the structure partially or wholly collapsing into the river. These will be followed in spring 2022 by further conservation work, including redirecting the spring into the cistern, supporting or rebuilding parts of the cistern and southern walls, and protecting the wall-head with turf.