leaks
Building may suffer from several types of water penetration, (for walls see section on Damp). A leaking roof will either be caused by 1) The failure of the roof covering, for example, missing slates, tiles etc., or 2) with problems where roofs change direction, forming a valley (see roof construction) or, where roofs meet a wall e.g. around chimneys. In these latter cases the problem may be with the lead flashing. Failure of flashing may be due to:- abrasion, i.e. from pieces of loose slate scoring the surface: fatigue: where too little allowance has been made for expansion/contraction causing the lead to crack.: or, creep, where the lead has stretched under its own weight again causing it to part company. It should be noted that lead is also susceptible to corrosion due to lichen on roofs and contact with lime in cements and mortars. Rainwater goods are also naturally susceptible to leaks, for example where elements, such as cast iron gutters have corroded. (Siker, 2018)