I suspected woodworm infestation in the timber of a double garage roof but had no idea of the quantity of product needed to coat that amount of wood. Fortunately I chose Permagard which, in a 1 litre concentrate, could be diluted with water to 25 litres and applied it with a spray. In less than 2 hours we had protected equipment in the garage and applied 2 coats to all the timber, a process that I had originally thought would take a couple of days. There is just a little Permagard left over in case of further problems. This has been a very satisfying experience.