I've got a coupl of hair-line (well almost) cracks in the external rendr of my house. It's a red brick house. In one location on the inside of the house directly opposit on of the cracks is some dampness. Could I 'scrape' out the cracks and then re-fill with something to seal? It looks like that render is a sand and cenment render with some lime in it. What is my best course of action without costing me hundreds if not thousands of pounds?