Hi I’m building a 2′ cmu retaining wall with rock and mortar face. For drainage I’m using a 3″ perforated pipe, crushed gravel, and landscape fabric my question is are weep holes necessary? BTW I live in SoCal so not too wet although it will have grass above
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If the wall is mostly water-tight (vs being, eg, stacked landscape blocks with no mortar) then you need drainage of some sort. You can get away with weep holes (ideally backed by gravel and landscape cloth) or you can use a perforated drain line (which actually drains somewhere), so long as it sits near the base of the wall. No need for both.
I guess where my dilemma is that my perf pipe will have to sit 6" above the footing so that it can exit the wall above ground. At that position will it be too high to do any good? Thanks for responding
Not entirely kosher, but in California, with a 2 foot wall you'll probably be fine.
Of course it can exit at that height.
Exit 6" above the footing? Of course it will. If it didn't, you'd have your footing exposed on the face side of your retaining wall. There is nothing un "kosher" about drain tile existing at that elevation because if you any finished grade at all on the face side of your wall, then it has to exit near that height. The whole point of your using drain tile and gravel behind the wall is to relieve hydrostatic pressure against your wall. You have very little, if any, building up at 6" above your footing.
BTW I believe the IRC 404.4 doesn not require design work for wall 24" and under. That means that the IRC is not worried about retaining walls of this height from a structural perspective. However, It is generally a good idea to observe a safety factor of 1.5 in your footing width and run drain board all along the back of your wall before you install your drain tile and gravel. It's kind of a belt and suspenders approach on the drain tile, but it is a sure way to maintain a capillary break between your masonry and backfill. In turn your masonry will probably look better over time (reduce chance of efflorenscence) and last longer.