I'm really torn about whether to use filter cloth for my foundation perimeter French drain. My geotechnical engineer says not to use it because he has determined that our surface soil is silty, and claims he can tell this just by looking at it. However, I've heard from various neighbors and even a home inspector that we have clay soil! He suggests using CALTRANS Class II Permeable drain rock instead, which he believes will work fine without a filter cloth. I'm a total newbie in this area and would love to hear your thoughts. Is it typical for a geotechnical engineer to assess soil visually? Also, does it seem accurate that I can skip the filter cloth? Any insight would be greatly appreciated!
2 Answers
I totally get your frustration! It seems like for every expert, there’s a conflicting opinion out there. Some people have had success without filter cloth, especially if the right materials are used. But you’re right to question the visual assessment of the soil—it's not typical for an engineer to rely solely on that. Maybe consider getting a soil test done for peace of mind? At least that way, you'll know exactly what you’re working with!
This whole filter cloth debate can definitely be confusing! From what I've read, some folks swear by using it to prevent soil clogging the drain, but other experts argue that if you use the right type of graded drain rock, like what your engineer recommends, it can work just fine without filter cloth. It sounds like your engineer has good reasoning since the drain rock is designed to filter out particles, but it's always a good idea to get a second opinion from another local expert if you're unsure. Trust your instincts, and make sure you’re comfortable with the final decision!
Thanks for the reassurance! I really appreciate it, I might just seek another opinion to make sure I'm doing this right.
Yeah, a soil test sounds like a smart move. Thanks for the advice! I really want to make sure I get this right.