How shall I cover these cracks in the oak wallplate before putting the slates back? Any accidental water would sit on the oak, creep down the cracks in it and by the brick chimney and rot it. The cement render on the wall originally came to above the top of the oak, there was a line of bricks along there – but the lime mortar had changed to powder so there was no protection against damp – which would have stayed in there and had no air to dry it out. Maybe I should put a roof batten on top of the oak and then a plastic vent? And fill the gaps with wood glue? Or paint the top of the oak? and what about the gap between the oak and the chimney brick – silicon mastic? Suggestions please….