Drainage around building

[kberjian]

Morning,

I am building a 50x60 shop and it is cut into the side of a gentle hill (about 3' difference in height over 50'). I have eaves on the building that will bring the water off the high side down around to the low point but I am concerned about the water from the top of the hill coming down against the shop. I am thinking of installing a perforated pipe along the high side, continuing on the ends of the shop, and draining downhill past the building. The soil around it is very hard natural clay, I was going to run a 4" per pipe surrounded by wash rock about 10" deep, then with a geofabric on top to keep out sediment, then covered by rock on top. Thoughts?

 

[Bondo]

but I am concerned about the water from the top of the hill coming down against the shop.

Ayuh,.... Just cut a swale above the buildin' to divert the water around it,....

 

[Cougar]

With landscaping you could channel the water around the building.

 

[larry_g]

I did as Bondo suggested. At the top of your cut, taper back the slope so that the water coming down the hill hits the swale and moves off in one direction or the other. I still have the french drain as you diagrammed above, just use the swale to divert most of the surface water before it gets to the cut. You can see some of the work in my build below.

lg
no neat sig line

 

[kberjian]

Appreciate the feedback.

 

[rburke65]

I just had my excavator guy come back and do that very thing. He cut in a swale to divert the water from my concrete drive there by directing it to beyond my shop. Can't believe the water that it redirects. Much better and there is nothing to clog or maintain. It's another tool to keep me dry. Plus there isn't any material to but....well maybe grass seed.....

 

[steveo1o9]

Yup cut in a swale to divert all runoff around your building. A french drain is not meant to collect surface runoff, especially on a slope, but rather collect and divert ground water.

 

[kbs2244]

The swale is the way to go.
Whatever you, do not ever direct water toward a building.

 

[beakie]

swale yes

but add perf pipe around perimeter about 1' below surface, 6" of clean 3/4stone with landscaping fabric over it and soil over that.

also ensure your slab is a well above grade on top side, the ground will settle downhill towards shop over time effextively raising grade a bit.

my shop has just the swale, orginal "grade" has risen a few inches since grass growing and now slab is just @ grade and I get water in shop in spring (bought this property, not my design)

I expect to put perf pipe eventually to rememdy this situation.

 

[theoldwizard1]

This is typically called a French drain. If you are just in the planning stages, I would plan on doing it ! Your trench needs to be about 2'-3' deep.

The geofabric needs to be laid in the trench FIRST, with plenty of surplus hanging out. 3/4" - 1" crushed/broken stone/concrete can be used. You also want a sock over the pipe. Lay some of the stone on the trench first so that you can adjust the pitch of the pipe. Carefully cover with the other stone making sure not to break the pipe to a depth of about 6". Fold in the remain geofabric and cover with decorative stone.

I am not saying that swales or other landscaping will not work, but this is your last line of defense.

 

[ard]

I dont like the hillside sloping TO the structure with only the width of the trench- Id want 4 to 6 FEET sloping AWAY from the building before then rising to the current grade. Period.

Id ALSO cut a healthy swale on the top of the cut, say 6 feet from where your cut meets the natural contour.

See how that works. Should be 2-3 hours with a cat. Cost will be far less then fabric, rock, yada yada

You can always go back and trench for a drain at the 'bottom' of that 4-6feet clearance.

 

[kberjian]

So current plan is to install 4" rigid perf pipe around the perimeter of the shop about 8" deep covered in 3/4"wash rock similar to the picture I had above. I am also thinking I will tie the down spouts into this pipe system too? Thoughts? I had down spouts on all 4 corners so they would be hard piped in. Rough overview of the shop is below. The pipe would be buried under the concrete apron in front of the doors.

I will also be changing the grade above the shop to be more slopped away from it.

 

[CNGsaves]

^ ^ ^ That's going to be a nice 50'x60' shop OP !!

Keep the pics coming as we GJer's just LOVE new builds.

+1 for the inverted V swale at top of shop to divert water around.

Those posts are little unusual with the treatment on bottom . . what are they ??

 

[ard]

. I am also thinking I will tie the down spouts into this pipe system too? Thoughts? I had down spouts on all 4 corners so they would be hard piped in.

I would have a separate run of solid pipe to drain the downspouts.

You dont want all the roof water to be directed into the perf pipe and fill up the trenches with water, every storm.

 

[Firebrick43]

I would have a separate run of solid pipe to drain the downspouts.

You dont want all the roof water to be directed into the perf pipe and fill up the trenches with water, every storm.

+1 on both accounts.

Two pipes, on perforated, one solid. They cand join 25 feet or so past the building. And a swale 6' out.

 

[kberjian]

I would have a separate run of solid pipe to drain the downspouts.

You dont want all the roof water to be directed into the perf pipe and fill up the trenches with water, every storm.

Good call on the separate solid pipe for the downspout tie in. Was an oversight.

 

[yeldogt]

I have the exact situation. We cut a swale back from the building on the high side. I have footing/ foundation construction and a french drain on the inside under the slab and one along the outside footer -- Pipe is cheap when you are building new.

The french drains and the downspouts are on separate pipes to the street -- culvert. I also put drains in the swale -- mostly to keep any water off the driveway in heavy rain.


I would not direct water at the building with the hope the pipes will take it all .. and clog and you will have water in the building

 

[theoldwizard1]

So current plan is to install 4" rigid perf pipe around the perimeter of the shop about 8" deep covered in 3/4"wash rock similar to the picture I had above. I am also thinking I will tie the down spouts into this pipe system too? Thoughts?

I would go a full 12" deep and then line that trench with geotextile/landscape cloth so that no silt can some up. Place a couple inches of the rock in the trench. This will make it easier to adjust the pitch for proper runoff. Add rock until it just covers the pipe. fold the landscape cloth in and then add the rest of the rock.

No problem hooking in the downspouts.

 

[MagKarl]

I would cut that high side bank back a lot more if I were you. Slope it away from the building and wide enough for a tractor to do the work. I'd spend your time and money on grading work, not on drains that may fill with silt and leave you with a muddy moat around your new building.

If you want to pipe your downspouts out, use separate solid pipe.

 

[yeldogt]

If the pip is 6" -- You should be good with a common pipe as long as the downspouts line in away from the building. I would not do it with 4" -- they clog to easy. You don't want a back up in a heavy rain

 

[ard]

If the pip is 6" -- You should be good with a common pipe as long as the downspouts line in away from the building. I would not do it with 4" -- they clog to easy. You don't want a back up in a heavy rain

Really? You'd run the gutters down into 6 inch PERFORATED pipe to drain the roof??? Every single sprinkle or shower you will be injecting water into the earth around the structure.

One pipe to drain roof, separate pipe to drain rock. Ideally there will be no water in rock if graded properly.