New shop drainage problem

[Brian Austin]

Everything has passed inspection on the new shop except a drainage issue between a wall fence and the foundation of the shop. As you can see from the posted pics (hopefully this works, first time), the six foot wall sits on a footing, about 8-12" deep, depending on area. The building foundation footing (monolithic pour in AZ) goes down 24" (weird design with building manufacturer, Tuff-Shed).

The wall footing sits a few inches higher than the foundation so water will drain toward the building. If I cut too far down on the wall side, though, the footing will lose support and the wall will have issues later.

What I was thinking is cutting a deeper channel down the middle, sloping both sides toward the center channel and sloping the channel toward one end of the building, where water would flow into the front yard and street. The whole area will have a minimum of 2" of 3/4 gravel/rocks covering it after all is finished.

What do I line the channel with? Is this even a viable option? I need to pass inspection but the inspector wouldn't tell us what he's looking for (I swear they're making up the rules as we go along). Any other ideas?

Thanks for any input!

[Roger Fitzsimonds]

Hi Brian,

I would cut the trench deep enough so the of the trench is lower than the shop and then put the black drainpipein. Its about 4 in in diameter and they make a sleeve you can put on it so ithe pipe wont fill witjh dirt over time. or you can wrap it in landscape cloth. then cover it with the gravel.

Hope this helps
Roger

[Brian Austin]

While shopping this afternoon, I looked through some books at a bookstore. Found some techniques for drainage issues like this. It may be an option but I'd appreciate hearing from someone who's done this before.

Instead of a center channel, I would leave the slope in place and dig a trench right next to the foundation. Then I would place a 4" drainpipe, sloped to one end of the building and extended beyond it, on a bed of gravel. The idea is that drainpipe "catches" the water and moves it beyond the building.

Is this better than my original plan?

[Jim Becker]

I think you have the right idea, Brian, although I'd probably put the drain as you describe a little farther from the building foundation so you can have a "little slope" there, too. In fact I probably would use some tile or flagstone to line the slope along the building foundation to insure water careening off the property wall was always directed into the drain as it came down the slope. Ideally, this would have been done before the building got built, but no good workshop rasing goes unpunished, especially if a building inspector is involved! :D 'Coulda used a small backhoe then instead of a shovel! (Power tools are sometimes a nice option when it comes to moving dirt!!) It really irks me that a) it didn't come up earlier in the process and b) he will not tell you what he is expecting you to do...specifically.

[Tony Falotico]

Sounds like a good plan, but follow Roger's advise and wrap the stone & pipe with a filter fabric to keep the fines from clogging it up. Hate to see ya have to dig it up in a few years and re-do it.

[Rich Konopka]

I have all of my down spouts connected to the 4" black pipe and it is buried and takes the water away from the house to a huge dry well filled with crushed stone and the pipe is perforated with mesh filter fabric. I had this done when my house was dug by my contractor with a back hoe.


HTH

[Arvin Brown]

What you are looking for is called a "French Drain". To construct one follow the following steps:

1) I would place this drain right down the middle of the space. The finished grade would then need to slope to this area.

2) From the beginning point of the drain dig a trench about 18-24 inches deep and about 8-12 inches wide. Make sure the trench slopes at 1/4" for every foot of length.

3) Install a landscape fabric in the "U" that you created for the trench.

4) Install approx. 1" to 1-1/2" of 3/4" rock.

5) Install a geofabric encased 4" perforated drain pipe (from Home Depot or Lowes). Make sure the holes are at the bottom of the pipe.

6) Fill the remaing portion of the hole with the same 3/4" gravel up to about 2" from the top.

7) Finish filling with a coarse river sand.

8) You can decorate with the river rock and pretend it's a dry stream (I lived in Tucson so I know what this is).

You can reference the attached sketch.

[Jim Becker]

Brian, any chance that space is wide enough that you could use a rental trencher to do the hard digging work?

[Brian Austin]

I'm not digging 18-24" deep again. I did that for the electrical service and it sucks, especially when the electrician gave me less than 24 hours notice that he was coming out.

Besides, if I dig it 18" down, then it's well below the rest of the grade on the downhill side, with nowhere to go.

No, I'm pretty sure a rental trencher won't fit there. It's about four feet at best.

I'll put a 4" perforated drainpipe (wrapped) in a 10" trench, with small gravel in the trench, both below and above the pipe. It will drain toward a 'dry streambed', similar to what I've seen in Tucson as Arvin mentioned.

If it gets too bad in that area, I'll add a rain gutter system to the shop later.

Thanks everyone!

[Rob Russell]

Brian,

Based on some drainage issues we've had around our addition, I wouldn't count on much seeping down through sand. If you have coarse rock, like 3/4" or larger, you'll get some fair drainage down through.

Your idea of the 10" trench, but with sloped sides, should work fine. You need to direct the water to where you want it - don't assume it will just run off. Those periodic gully-whompers you get will dump enough water so the 4" pipe will overfill and you want the slope of the trench to channel the water away from the shop/wall and down to the dry-stream.

[Ken Toupin]

Bryan , use the french drain /// as a construction manager I have been there and done that //// the french drain will give you the results that you want.. Ken T