I have a two story wooden farm hause built around 1900. The houses foundation is brick on clay soil. The crawl space is low 18-20 inches in most places. If I wanted to remove soil and make the crawl space deeper how far away from the foundation should I stay. I read somewhere for each 1 foot of depth you would need to move away from the foundation the same amount. For example if I wanted a crawl space 3 feet deep I would need to stay away from the fundation by 3 feet. Any feedback would be appreciated. Thank you