Dry rot is a fungus that feeds on and destroys untreated timbers in buildings. When active, the fungus gives off a distinctive mushroom smell. The dry rot spores (similar to tiny seeds) can be assumed to be almost everywhere. Older building timbers (pre 1930) that may not have been pre-treated to protect against rot, will be particularly at risk from dry rot. Dry rot affects timbers located in damp, humid parts of the building which lack adequate ventilation. The building parts most at risk are sub floor voids, roof spaces (especially under flat roofs) and first floor (or above) timber floors affected by leaking sanitary/plumbing fittings (especially shower trays). Once the dry rot becomes established, it can quickly spread to affect other timbers, not affected by dampness. It can pass over and through walls and typically travels behind internal timbers such as skirting boards and timber panelling. Dry rot is a very serious defect and is both costly and disruptive to remedy. The cause/s of the dampness will first need to be remedied. Then all rot affected and nearby timbers need to be cut out and be burned, prior to their replacement with new pre-treated timbers. Similarly, all affected plasterwork will need to be removed and the walls treated, prior to re-plastering. Where possible, ventilation should be provided or increased (such as floor voids and roof spaces).