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bhry 09-22-2010 11:47 PM

Foundation Drainage
I have an old barn that was moved to its present location in the 1960's. It was built in the early 1900's and is about 2,000 sq ft. It is like a bank barn (with a wooden floor), but the lower part is only a crawl space.

The foundation was not built correctly. It was built with concrete blocks, but there is no reinforcement (cement or rebar inside the blocks). The barn actually just rests on the blocks, there is nothing that ties the sill beams (which are large oak beams) to the foundation. It is built into a small is about 3 feet higher on one side than the other. The wall on the downhill side is leaning over rather severely. I believe it is being pushed by the opposite side of the barn, which has all the dirt pushing against it, since it is on the uphill side. The barn itself is not leaning yet. I have installed diagonal braces, set in concrete, pushing back against the leaning wall to prevent it from moving any further.
The gutters are functional, but it is in an area with a high water table. Certain times of the year, the water table is only a foot or less below the surface, and any hole dug will fill up with water. I have dug out the foundation all the way around the barn, down to the footer. It is 4 feet down to the footer on the uphill side and about 2 feet down on the downhill side (the footer has "steps" in it so it is not all at the same level). I pulled out many large pieces of concrete (looked like old sidewalk pieces), some weighting hundreds of pounds, and misc broken concrete blocks and such that were used as back-fill. These were pushing in on the wall and damaged it in some places. I might eventually put a couple concrete piers under the damaged areas, but not right now.
The footer extends under the wall about 18" on the outside and does not extend inside at all. There is no drainage tile. The reason I dug it out is so that I can lay a drainage pipe, but I have some questions about how to do this.
I am planning to lay perforated plastic corrugated pipe on top of the footer. I know some people say to lay it beside the footer, but I don't want to dig my trench out wider and there is no basement here to keep dry (like there would be on a house). The main reason I need drainage here is to reduce the force pushing on the walls when the dirt is full of water, especially in the spring.
The pipe will run out to a daylight drain about 50 feet away.
Should I fill my entire trench in with gravel? Or gravel on the bottom and dirt on top?
The soil here is about one foot of top soil and then heavy clay below that. I don't want the dirt to clog up my drainage pipe, or to get mixed in with my gravel and defeat the purpose. Should I line the edges of my trench with something?
I have heard some people say to wrap the pipe with drainage filter fabric, and others say not to use it because it will clog up and not allow water to pass through. I am thinking about installing a vertical pipe at each corner, tee'd into the drainage pipe, that will come up above the ground that I can use for clean-outs.
I need to finish this soon. I want to do this correctly without breaking the bank. And no, I am not going to build a whole new foundation. It would be near impossible to lift this barn because some of the floor beams are broken (from previous owner parking heavy eqiupment on them), and a lot of the weight sits on concrete block piers underneath the barn.
Thanks for any advice...

concretemasonry 09-23-2010 07:01 AM

For drain tile location, you would be far better off place the drain tilenext to and get the bottom of the tile slightly below the bottom of the footing You can do this as long as the tile is 1" away from the side of the footing for each 1" below the botton (45 degree line from the bottom of the footing and going out.

It is very possible you wall is leaning because the footing has rotated due to the extremely wet soil and drain tile will reduce the moisture under the footing.


Daniel Holzman 09-23-2010 08:44 AM

The topic of proper installation of perimeter drains (sometimes referred to in this forum as French drains) has been EXTENSIVELY discussed over the past couple of years, I suggest you search the forum and read through the threads. You will find that it is essential that the pipe be surrounded by freely draining material (typically crushed stone) up to the surface, and it is almost always recommended that the pipe be encased in filter fabric to prevent migration of fine material into the pipe, which would clog it up. There are numerous other discussion threads regarding appropriate pitch, location of the pipe, protection of the pipe from frost, depth of burial, and performance issues, but you can find all of that on this forum, no need to repeat it here.

rtoni 09-23-2010 10:08 AM


Originally Posted by bhry (Post 505872)
I am thinking about installing a vertical pipe at each corner, tee'd into the drainage pipe, that will come up above the ground that I can use for clean-outs.

fwiw - I did this on every corner of my foundation (crawlspace footings) - same soil conditions. I'm not sure if this is recommended or good practice or overkill etc but it was an easy thing to do. So take heart - if this is a crazy idea at least you're not alone :jester:

One suggestion in the thread below was around using a device to prevent the flow from your hose from exiting back out the cleanout itself, instead of being forced down to the pit where you can remove the silt. Reading that post I started to wonder if maybe a lot of clean outs would actually be a problem in that regard (water backing out any of them when you're trying to flush the whole system). Mine are capped with those removable plastic end caps they sell at the box stores so I'm hoping it's all ok, but in the few years it's been in service, I've never flushed it out. I do get a lot of water moving thru there especially in the late fall (heavy rains) and early spring thaw.

Doing a more thorough search as suggested thru the forum for related info might speak to this point and other issues more clearly. Just tossing in my own experience fwiw...

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