Garage - Exterior Drainage

[stein]

Update: added photos

Photos show the garage from the front sloping from the road. Driveway material/condition. Sides of garage and general grade of property. There isn't much slope from where the garage is to further back on the property. This property is lowland and backs up to a watershed.









Hi all, I have a detached 2 car heated garage that I treat as a shop. I've only owned the property since November, and learned the hard way during some late winter rain storms and the spring thaw that the yards drainage situation kind of *****. I ended up with a few inches of water in the garage, but fortunately didn't have too much "nice" stuff stored in there yet. I want to prevent this from happening again. I know there are potentially many solutions, but looking for the most optimal solution that doesn't break the bank.

During the worst of the water coming in, it appeared most of the water comes in through the main garage door. That particular driveway slopes from the road to the garage. Though I've noticed this summer that another source of water is from the sides leaking in between the slab and bottom plate. A potential third source is water backed up into the garage floor drain.

In short, the grade of the yard is not ideal for this garage and it would have been better for the garage to at least be blocked up to prevent the water seeping in from the sides.

I'd like to avoid raising the garage and instead do the following:
- Add gutters to the garage to mitigate water coming in from the sides
- Add drain tile around the garage in a horseshoe shape (opening of horseshoe toward back of garage)
- Add some shallow ditches on either side of the driveway

I'm interested in other peoples thoughts and if these sound like they might potentially work. I'd love to also finish the driveway (it's currently dirt/rock/asphalt) and include a trench drain before the garage door, but that is a project for the future.

Thanks in advance

 

[kbs2244]

Foe sure gutters with downspouts run 10 feet , down hill, away from garage.

The driveway is a bigger problem.
Does it have any slope to the side as well as down to the door?

If you can grade it to the side into a swale (a wide shallow ditch) leading further down hill, past the garage, it would be ideal.

A trench drain going into the swale would be the finishing touch.

 

[meboatermike]

Where does the garage floor drain drain too? Is that drain clear and can you keep it open so it does not back up?

I know you don't want to raise the garage but a row or two of blocks would gain you 8-16 inches that you could use to both raise the floor and slope the drive from outside the garage door towards away from the garage. That could potentially go a long ways to getting the garage up away from your water I would think.

 

[Higgins]

Is the driveway Cement or Gravel?

Would it be possible to regrade the gravel and slope it either left or right side of the driveway. If cement or asphalt, you could cut out ~20 ft of the driveway and slope it to the middle, then slope it either Left or Right away from the driveway.

 

[Glory]

All your ideas are good and should be done. Make sure the drain tile is socked and that the trench stone is burrito wrapped with the geotech fabric (marifi).

For the driveway, just saw cut a thin section and tie one of these to your French drain outlet pipe. https://www.ndspro.com/products/drainage/channel-and-trench-drains.html
Locate it immediately outside garage slab, parallel against the slab on the garage door opening side.

Oh - make sure your drain tile actually daylights... even if you have to trench a long ways. It will be worth it.

 

[DGersic]

The gutters and the drain tile have to drain to somewhere. Do you have a destination for all that water?

I’d be checking out that floor drain. Where does it go?



Sent from my iPad using The Garage Journal mobile app

 

[Bretny]

Wheres the pictures?

Most water issues can be helped with just proper grading. As a last resort add things like pipes. Pipes fill with dirt and can be clogged or colapse. Try to catch and redirect water as far away from the garage as possible. Dont try to catch all the water 4in from the slab and expect it to catch it all.

I helped a friend with watet getting in his garage. Most of the water was redirected with a simple swale that moved water down to the road.

 

[Innovate1]

Shallow swales can be quite effective. You didn't mention if you have anywhere lower to discharge water to. Once owned a property that was the original house on land that was developed with other houses. A garage was build behind the house and below street level and very low relative to the ground around it. Some of the neighbor lots had built up the back yards so they were higher. Driveway sloped down to the garage. Adjacent houses had sidewalks and curbs so water followed curb to our drive and ran down the drive. We put in curb and sidewalk so water continued down street. Then small swale around garage including across gravel drive. Required us to clear out the swales from time to time as they would tend to fill with sediment. Would have been MUCH better if the garage was even a few inches higher but we were able to keep the water out. Didn't have any lower spot to discharge water to but some neighbors lots were about level and provided path for surface water.

 

[strutaeng]

Yeah, as long as you have adequate slope, your plan sounds good. Do a channel drain on the driveway.

For the other sides install some catch basins. I like catch basins because they can easily be cleaned out. The french drains with socks tend to either get clogged at the socks or get filled with dirt, depending on the soil type you have.

I personally prefer solid pipe over corrugated. Solid pipe has a better flow coefficient and can be snaked out, plus since it is rigid, the slope is constant instead of getting low spots with corrugated. Leave a clean-out to make snaking down the road easier, but you can also snake though a catch basin.

NDS has some nice calculators for sizing pipes.

https://www.ndspro.com/drainage-calculator/

Post some pictures.

 

[strutaeng]

https://www.ndspro.com/tools-and-calculators

This one is the most helpful. You can see a huge difference corrugated vs smooth:

https://www.ndspro.com/drainage-pipe-calculator

 

[theoldwizard1]

In short, the grade of the yard is not ideal for this garage and it would have been better for the garage to at least be blocked up to prevent the water seeping in from the sides.

I'd like to avoid raising the garage and instead do the following:
- Add gutters to the garage to mitigate water coming in from the sides
- Add drain tile around the garage in a horseshoe shape (opening of horseshoe toward back of garage)
- Add some shallow ditches on either side of the driveway

I have been there ! My French Drain and Dry Well Project

Gutters will help, but probably not enough.

First, you need some where for all that water to go. In my case I had to dig that dry well. It still occasionally overflows (the combination of snow melt and spring rain), but the water will dissipate in a day or so (it used to pond for 3-4 days in a heavy summer rain).

First, if the driveway is pitched toward the garage, you need to cut the driveway and install a channel/trench drain across it. Connect it to french drains (drain tile) buried about 12" deep along each side of the garage. Use the solid kind with a "sock" pulled over it.

Again, where ever you are sending the water had better be able to handle the volume ! Worst case scenario, you will have to dig a sump and install a pump. Back Yard Sump System, How to Install

 

[Bretny]

If i drywell would work most likely you wouldnt need a drywell..unless you have layers of dirt like so. Topsoil, clay, a good draining soil like sand or stone.

Here im on mostly all clay. I rely alot on surface run off to drain areas. Im not at the top of a hill nor the bottom. I use to have an area that collected water and would be there most of the summer breeding mosquitoes. I filled the 75'x300' area with wood chips, some areas are over 2' deep. No standing water this very wet spring and alot less mosquitoes. Im sure the chips act like a sponge and will sink over time but i have not paid anything for the chips, no material fee or delivery charge and there natural.

Do you have a slope to work with and can the ground freeze and you get rain? If yes then a drywell is not a good idea.

 

[rattle_snake]

I'll just throw this out there...
https://www.garagejournal.com/forum/showthread.php?t=371545


Easy enough.

 

[stein]

Thanks kbs2244, I just added photos of the garage to give everyone a better understanding of the situation.

 

[stein]

Thanks everyone for all of the great feedback. I did add photos to my original post to give everyone a better understanding of the situation. After reading yours responses, it seems some of you have encountered similar situations.

 

[kbs2244]

As far as gutters go.
Do the math.

How many S F of roof are you draining compared to the S F of driveway?

 

[strutaeng]

It looks like you have plenty of fall to the rear. It looks like at least 2-3' of fall to the mow-line!

You can put a stake with an inexpensive level on a string line to measure it.

I think your problem is really easy to solve: Put a trench drain across the garage door and run pipe along the side and take it out about 20' beyond the garage. Add cutters and a catch basin at the downspouts and tee into the drain pipe.

The real problem is when sites don't have enough fall to use a gravity drain system. You have to rely on dry well, which don't work in certain types of soils, or sump pumps, which you have to do regular maintenance to keep them running. Gravity systems are much better, as long as you have fall and drain to daylight.