Browse Forums Landscape & Garden Design 1 Nov 21, 2013 7:22 am Hi all, I'm mostly across this but I need to confirm a few things to get finished. Just quickly, it's a small (600mm) funtional retaining wall about 4.5 meters long, using 200mm x 75mm treated pine sleepers that will sit three high. After browsing Bunnings the other night, my questions on drainage: 1. What diameter pipe do I need and what does it have a bearing on ? I was looking at 50mm socked Ag pipe. 2. At the inside base of my wall, does the ag pipe lay on the surface (ie clay) or does it sit on the screenings? Not sure of the theory of how this works. Obviously there will need to be screenings on the top of the pipe for it to work. 3. There's no chance that the ag pipe will be connected to storm water, so I'm going to just run the pipe out through the bottom of the wall (through the bottom sleeper). Apart from aestetics, is there any problem with this in terms of wall drainage function? 4. So, no geofabric necessary? Just the socked ag pipe and screenings will do the job? Any help appreciated. Cheers, HC Re: Retaining wall drainage questions 3Nov 21, 2013 8:57 am Would be flowing towards the retaining wall. The back yard slopes downwards from the back fence towards the front fence. The retaining wall runs parallel to the back fence. Re: Retaining wall drainage questions 4Nov 21, 2013 12:41 pm Using geo fabric as an extra measure to keep the screenings cleaner for longer is always a good idea IMO. When I built my back yard wall I too did not want to lay the ag pipe straight onto the clay behind the wall so what I did was roll out my length of geo along the wall with the edge of the geo sitting tight against the base of the wall. I then placed the ag pipe on the geo along the back of the wall and then placed my sreenings on top and filled to the required amount. This method results in the ag pipe not sitting on/in wet clay forever. Given you want to bring the water through your wall. What happens to the water once it appears at the front of the wall? Need to ensure the water does not cause a secondary issue for yourself. Is there another drain etc the water can get to?? Re: Retaining wall drainage questions 5Nov 21, 2013 4:47 pm Cheers. So is getting a socked Ag pipe the same as using the geofabric or is this something different? Re: Retaining wall drainage questions 6Nov 21, 2013 5:02 pm I always used to use geofabric.......But in the civil engineering industry there is a move away from using it as a filter, because it works too well and gets clogged. Now I just use plain slotted pipe(no sock) and plenty of screenings. There is a detail of a sleeper retaining wall here: http://www.anewhouse.com.au/2013/06/ret ... l-details/ The Harder You Try - the Luckier You Get ! Web site http://www.anewhouse.com.au Informative, Amusing, and Opinionated Blog - Over 600 posts on all aspects of building a new house. Re: Retaining wall drainage questions 7Nov 22, 2013 2:52 pm Here is a pic of how I built my main retaining wall, 800mm high x 34m long. Note: The inverted toe in the footing is there as a mowing strip. http://i459.photobucket.com/albums/qq311/EB_Photos_2009/WallV20v1.jpg Re: Retaining wall drainage questions 8Nov 22, 2013 3:01 pm Awesome thanks guys. We're almost getting close to fining the answer points 1 & 2! Basically I'm still unclear as to whether I need to put Ag pipe on clay or Ag pipe on geofabric on clay Ag pipe on screenings Ag pipe on geofabric on screenings .. or the same options again, but socked Ag pipe in stead of geofabric (assuming the socked and the geofabric do the same thing) And whether or not I need bigger that 50mm pipe. Thanks for the info/diagrams on the on the wall. I've got that covered. It's just the drainage I want to clear up in my head. HC Re: Retaining wall drainage questions 9Nov 23, 2013 5:36 pm As per my diagram. Ag pipe on geo on clay. 100 mm diameter Re: Retaining wall drainage questions 11Nov 24, 2013 12:26 am 100mm won't clog as easy. Also allows for water to be drained quicker without effecting the retaining wall. Re: Retaining wall drainage questions 13Dec 03, 2013 2:24 pm Hi mate, I recently built a retailing wall at my place. You need to put the geo fabric behind the wall in a "U" shape, with the slotted ag pipe at the bottom. This must sit lower than the base of the wall (the bottom sleeper I mean, not the post). Then fill the U with drainage gravel (I used recycled concrete gravel). Here are some pictures that show what I mean, along with my wall: http://imgur.com/a/B3VUR Not sure what council area you are in. Some LGA's allow zero lot retaining walls. This usually occurs in greenfield developments but not often in established areas. You… 1 5648 4 8750 Thank you again Simeon.. I will call my certifier for that. Have a good day 4 1330 |