The discovery by official inspectors also included a stained mattress and significant levels of dust in bedrooms at Fernbrae Hospital in Dundee.
Staff were also unable to identify the correct products for cleaning up blood and other bodily fluids at the BMI Healthcare-run site, according to the report into the unannounced visit by Healthcare Improvement Scotland (HIS).
Susan Brimelow, chief inspector of HIS, said the visit had identified a number of significant areas for improvement.
She said: "We had concerns about cleanliness and compliance with standard infection control precautions. In particular, we were not satisfied that there was an adequate system and process in place for the continued monitoring of domestic cleanliness and actions taken to reduce the risk of infection for people using the service."
It is not the first time HIS has raised concern after inspecting Fernbrae, which has 15 beds. In 2012, for the category "quality of the environment" it was given an "adequate" rating, although issues raised in that inspection report have since been dealt with.
The inspectors made their latest surprise visits to Fernbrae in October and November last year. The report of their findings, published yesterday, rated the quality of the environment as "weak" and the management and leadership as "adequate", while care and support, and staffing were described as "good."
It said during the October visit that inspectors were concerned about infection control and listed 14 different issues ranging from damage to the fabric of the building to inappropriate waste disposal.
Two patients were interviewed, and they commented on the attentiveness of the nurses but also said the building was "tired."
Louise Buchan, executive director of the hospital, said they took the recommendations very seriously. She added: "High standards of hospital cleanliness and effective infection control precautions are an important aspect of delivering high quality patient care, and we accept that there were some areas where our normally high standards were not being met. Patient safety and wellbeing is our first priority and we have taken substantive steps to address the concerns raised. We look forward to continuing to work with Healthcare Improvement Scotland to ensure the hospital meets the rigorous standards we, our commissioners, patients, and regulators, require." She said they were pleased patients spoke "positively about care they received".