How much stone over a footing drain line? – GreenBuildingAdvisor

Just posting this as the only way I can finish answering the OP named “mindgap”. For reasons unknown the thread has evaporated.

In my opinion the amount of stone to place around your drain lines will be driven by a couple of factors not least of which is the cost of the stone and the effort required to place it. I believe you asked if 10″ over the pipe is a good amount. I think that is a bit overboard for your situation, which I recall involves a hill. However, it is your money and your back.

Your soil type and grades both local and adjacent will largely control how much rain makes it down to your footing drains. I cautiously suggest that fifteen to eighteen inches of width adjacent to the footing would be enough to accommodate the fabric for burrito-ing the pipe, the fabric wrapped pipe and the stone to a depth of 4- 6″ over the pipe. There really shouldn’t be a river running through the system. The drain line is there to relieve excess water dropping down from the soil above and any dimple mats if used. This removes pooling against the footing and wall. The burrito wrap around the stone provides the square footage needed to pass water over the long haul as soil fines eventually accumulate against the fabric. The depth of the stone over the pipe could be less than 6″ as the pipe should be flowing faster than any pooling of water. I would go wider over deeper.  Then again, California has shown us some extraordinary rainfall levels. And remember the larger stone will have bigger interstitial spaces and flow faster.

Do not attach your downspouts to the footing drain. Keep those exit points at the surface and directed away from the foundation. Do be mindful of your neighbors and mind any local codes regarding runoff. I moved from a region where quite aggressive run-off mitigation was required. One home near mine practically had a moat around it.