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Drainage Dry Stack Retaining Rock Wall

Posted by GardenShananigans Pacific Northwest (My Page) on
Thu, Mar 28, 13 at 23:43

I have built two long, dry stack retaining rock walls (about 200 feet in length total) about three feet tall each. These are half man basalt rocks back-filled with drain rock (not brick, cast concrete stone or any other impermeable material, and no mortar) Each wall seems to drain rainwater fine through the rocks. Both walls remain perfectly stable as built after two wet winters.

I am now planning a third wall. I am planning on building this one the same way as the other two, but I wanted to see if anyone out there has more experience with dry stack. I am contemplating using landscape fabric or a french drain behind the base on this one.

I have read a TON on dry stack and there seem to be different schools of thought on how to ensure proper drainage. It appears from my reading that there are a few right ways to ensure drainage (one being the method I have used) and many other ways that lead to an unstable wall.

Anyone out there do this more than me and can tell me if I gain anything by adding fabric or drain pipe?

Follow-Up Postings:

RE: Drainage Dry Stack Retaining Rock Wall

If you have no fabric then you have nothing to prevent soil/fines from clogging up your clean aggregate. When we do a wall, we lay in the fabric behind, run 4" pipe along the bottom, backfill with 3/4" clean stone, and wrap the fabric over the top so you have a big ol' gravel burrito behind the wall.

RE: Drainage Dry Stack Retaining Rock Wall

While ancient walls have been built like yours and still stand, Marcinde's method makes it easier to guarantee that you won't have problems. Your wall looks like it has decent batter, but it cannot be determined from the picture if it's consistent throughout. I think this is one of the most important components of dry-stack retaining wall stability. Keeping batter sufficient throughout will help wall longevity. With greater batter comes greater stability and, personally, I like the look of it as long as it's uniform. You could easily create a wooden triangle with a level attached to gauge the batter uniformly.

RE: Drainage Dry Stack Retaining Rock Wall

Thanks for the input guys.

Marcinde: Your method makes a lot of sense. That was pretty much what I am thinking about doing. Do you use dry stack rocks or concrete blocks?

Yardvaark: I like your idea of the triangle. I actually have more batter than it appears in the photo in most places, but the triangle would improve the uniformity.

RE: Drainage Dry Stack Retaining Rock Wall

GS - it's cheap insurance we put behind ANY type of wall - stacked stone, CMU or poured concrete, timber, or segmental wall blocks.

RE: Drainage Dry Stack Retaining Rock Wall

No advice. Just wanted to admire :)

RE: Drainage Dry Stack Retaining Rock Wall

Thanks all. I am going with the drain pipe and fabric on this one!

Marcide makes a very good point: It is a lot cheaper and a lot less work to put the fabric and pipe in now than to have to rebuild the wall later.

Wish me luck!

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