Why is a rental damp in winter, and whose job is it to fix?

A household makes moisture constantly, cooking, showers, breathing, drying washing, litres of it a day. In summer, open windows carry it away. In winter, it meets cold surfaces and becomes condensation, damp and eventually mould. Whether that winter is miserable depends on two things: whether the house can shed moisture and hold warmth (hardware), and whether it is run in a way that lets it (habits).

The hardware half, the landlord's

• Extraction that works and vents outside in the kitchen and bathroom.
• Heating in the living room that is affordable enough to actually run, warm air holds moisture without dropping it on the walls.
• Insulation at current minimums, warm surfaces condense less.
• A dry subfloor: drainage doing its job and a ground moisture barrier where required.

The habits half, the household's

• Fans on during and after showers and cooking, lids on pots.
• Washing dried outside or in a vented dryer, not on racks in the lounge.
• A daily airing, even ten minutes of cross-draught in winter resets the indoor moisture load.
• Furniture off cold external walls, and curtains that let glass dry in the morning.

The fair split

Hardware failures are the landlord's to fix, and no amount of tenant virtue compensates for a fan venting into the roof or a swamp under the floor. Habit problems are the household's, and no hardware fully overcomes indoor washing lines and sealed windows. The productive move on both sides is the same: check the hardware first, write down what was found, and put habit requests in writing kindly. A shared record of that sequence is exactly what resolves it, or wins it, later.