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Bad drainage threatens home’s foundation

French drain may be best solution

Q: I live in an 8-year-old home in the Diamond Heights area of San Francisco. When it was built, a lot of excavation was done. The foundation had a lot of rebar, but below it was a lot of gravel. I was told that the gravel was there to improve drainage. During heavy rains, water collects under the house and seeps up through the floor in the front of the house. I can see moisture under the granite entry (discoloration of the stone), and some of the moisture has crept up some 2-by-4s and onto the drywall. Is there any way to create a drainage system? This happens only with really heavy rains. Or do I have to find a way to stop water from getting under the house? A: El Nino strikes again. Every few years, the ocean current warms up, affecting our weather. Normal winters bring moderate amounts of rain to the San Francisco Bay Area, but El Nino winters can mean torrential downpours. We're sure most readers remember when homes have been undermined and slid down the hills of Marin Coun...