Cromar Universal Wood Worm & Dry Rot Killer - 25 Litres Cromar Universal Dry Rot & Woodworm Killer can be used both to protect construction timbers against attack by woodworm and to give fungal protection. Typical uses are on doors and window frames, floorboards, joist roof timber and sheds etc. It is a clear solution and therefore can be overpainted or varnished when dry. It can also be used to treat dry rot fungal growth on brickwork and masonry. Approximately 6-8m2/litre - requires 2 coats.