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pcballgame 03-28-2009 08:12 AM

Adding drainage to existing retaining wall?
Hi all. I live in the North Shore Massachusetts area. My property has a cinder fill block retaining wall probably over 130 feet long with heights sloping from 1 ft up to 6 feet high on the other end. This wall was built back in the 1950's and it is the original wall. Due to having no proper drainage system, the wall is beginning to crack due to freezing and thawing over the winter time. I know this is caused by lack of proper draining system. Can anyone recommend what I would need to do to make a proper drainage system for this wall? I am a DIY and one day the wall will need to be replaced. Landscapers have quoted over $50k to remove and install a new wall system and the stairwell that is attached to it will also have to be replaced. It will take us a long time to come up with the funds but we would like to install a proper drainage system for the time being while we are saving for this future project and to avoid an early wall failure while we are saving. Any ideas on drainage greatly appreciated and thanks in advance. BTW, I saw something on TV about digging a hole every 4 to 8 feet with a fence post digger and dropping in PVC pipes (with holes ?) in the hole and stub the other end of the pipe out of the wall. May require drilling weep holes in front of the wall. Also backfilling the post hole with stones. I could not seem to find any information on such drainage system and what size pipe is needed for each post holes as well as what goes on top of the pipe when it stubs out of the ground. Thanks again.

Dugger52 04-13-2009 07:15 PM

You haven't got any answers because this is not an easy questions. The system you reference would work. I'd use three or four inch perfotrated pipe but I'm a little perplexed on how you tie the weep hole into the pipe.

Having said that the issue is the pressure behind the wall. No knowing how the wall is built or tied back into the bank makes this s little more difficult.

I think I'd get a couple of lengths of 2" or 1.5" diammeter schedule 80 PVC. I'd drill holes that were oversized by 1/4" where the problems were right at the base. Mkae sure these are 3' or so apart. Now you need to be careful because the whole thing could come down on you head and kill you. I'd take a 24" section of the pipe and angle at the end so it coiuld be used like a giant spoon to scoop the dirt out of the hole and do same. Take a section of the schedule 80 that is 2" longer than the wall is thick and insert it into the hole for drainage making it flush on the front. Try a few and see how it works.

pcballgame 04-13-2009 09:19 PM

I just want to say thanks to the person who gave the only feedback. I was also able to dig up information from This Old House web site. Here is the URL:,00.html I have also been keeping an eye on the television station to see if they show a rerun of what I saw in the past as I said in my last post and to date no avail. Soon I will start working on the drainage project.

Thanks :thumbsup:

Dugger52 04-14-2009 05:15 AM

I debated whether or not to do what was on the link or something similar. The difference is that you have a block wall that is showing damage and there wall was solid poured. In a perfect world you'd dig out behind the wall and lay perforated pipe in a gravel bed wrapped in geo-tex material and run it to day light. With a cracked CBS wall I'd perform the basics as I've outlined and see if that did the trick. If you get digging around behind the wall you could bring the entire thing down.

Do you know where the water is coming from? i would try to deal with that too, if possible.

LawnGuyLandSparky 04-14-2009 01:11 PM

I have to believe that if a 6' high, 130' wide cinderblock wall built in the 1950's lasted this long, it already has a proper drainage system, and the damage you're seeing now is just because a cinderblock retaining wall isn't going to last forever.

jomama45 04-14-2009 03:29 PM

It definately cant hurt to try drilling bleeders thru the wall. As stated before, run 1.5" pvc thru the hole & drill holes in the pvc in the conter. I think it's just as important to drain the water that is inside the block cavitys. Also, drill the holes as low to the ground as possible. You may luck out & find that there may be some drainage stone behind the wall.

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