I recently moved to Hungary and this is my first winter here. I was unable to inspect the roof properly when I bought the house as there was no ladder available to get to the loft. When I did get up there I noticed there were quite a few gaps where the clay tiles don't fit together accurately. This is due to the roof timbers not being straight. It seems to keep the rain out but we have been getting fine powdery snow which blows in through the gaps. Should I fill the gaps with mortar or is there a better solution to the problem? It is quite a big roof so I don't want to strip and re-tile it.