The gable window was leaking when it had rained on the brick wall. we could see the old steel intel had rusted and expanded causing gaps. The cavity felt tray behind must have failed otherwise water would not of entered above the window. we removed bricks and the rusty steel lintel we could then see the bitumen felt had failed as we thought. we fitted a new cavity tray, lintel and relayed the bricks inserting drip cassettes to allow water to leave the cavity.