drainage question

[Bakounine]

If all things go well, I will build a garage this year. There is, however, I few issues I need to deal with prior to doing anything.

The main one is how I am going to drain the garage. I would install Franch drains, but they would be below the level of my drainage trench in front of the property. They would also be below my house drains, so I would not be able to connect the two.

So, my guess is that I would need a sump pump in the garage, connected to the French drain I’d have around it, just like I have for the house. However, that would mean a 6.5' deep sump basin to accomodate the height of the foundation walls below slab level. Does such a basin even exist?

Also, I don’t plan on heating the garage constantly, so how would I be able to make sure the water in the sump basin doesn’t freeze (I’m in Canada, eh.)?

Is there any other poetential solutions? Anyone thinking out of the box?



Just a few extra contextual notes:

- My house is a split level with “dwarf” foundation walls (they are only 5' tall).

- When they build the house, they only dug up about 2', build the foundation and backfilled around the house to create a slope.

- I will build the garage one one side of the house. I have about 30' sloping from the house to the property line on that side.

- The garage will be 24' in width + an additional 2' away from the house. So I basically have only 4' slope from the garage to the property line, meaning I need to dig further in the ground to keep the garage foundation’s footing below freeze level (approx 4') and also ensure proper drainage.

Thoughts?
Thanks

 

[pipehack]

I cannot say that it wouldn't freeze.French drains are great as long as you don't put TOO much water in them. As far as a pit that deep. Yes BUT it will be VERY large in diameter. Be careful what kind of pump you use some cannot handle a lot of head pressure. You might be able to make a pit with a concrete form about 24" in diameter. Find a good cover for it . Maybe have one made from 1/4" plate for safety reasons. Just my .02

 

[kbs2244]

I don't think you have a problem.
As long as you do your gutters and downspouts so they go to the downhill side you should be OK.
Be sure to route any downspouts from the house past the garage.
If you have a sump pump in the house, route it past the garage also.
Perimiter drains and sump pumps are for protecting below ground floors.
Your garage floor will be at ground level.

 

[Bakounine]

Thanks guys.

If you have a sump pump in the house, route it past the garage also.
Perimiter drains and sump pumps are for protecting below ground floors.
Your garage floor will be at ground level.

Unless I am missing something, I would not be able to connect the garage drain to the house sump pump as the garage’s footing would be below the house’s footing. As for the sump pump idea itself, it was more to protect the foundation walls. If water goes under the slab and in the filling material, wouldn’t be pushing against the foundation walls during the freeze/thaw cycle?

I cannot say that it wouldn't freeze.French drains are great as long as you don't put TOO much water in them. As far as a pit that deep. Yes BUT it will be VERY large in diameter. Be careful what kind of pump you use some cannot handle a lot of head pressure. You might be able to make a pit with a concrete form about 24" in diameter. Find a good cover for it . Maybe have one made from 1/4" plate for safety reasons. Just my .02

The concrete pit idea may work, but why would it need to be so large in diameter? I was thinking of using a submersible pump that would kick in when the water reaches 18-24'’ in height in the basin.

BTW, the basin I use in the house does not contain any draining holes in it except from the the 4'’ inlet that is connected to the French drain. The French drain is at footing level and goes all around the perimeter of the house. I was thinking of using the same type for the garage.

 

[Bakounine]

Anyone else?

 

[Bakounine]

What it actually looks like (the trees will need to go down. )

 

[pipehack]

Here (Chicago) the minimum pit diameter is 24". I'm just passing on what our codes are. They are some of the most stringent in the country. The unions have a lot to do with it.

 

[buening]

One thing to keep in mind is where your water table is. Typically this isn't a problem, but there are areas where you can dig 3' down and hit water. A french drain is useless in high water table areas.

Is your garage detached and in the back yard (low land according to the pictures) or is it going where the red VW's are parked?

 

[kbs2244]

You have a fair amount of fill on that lot.
You can see how you house sits higher than the original grade.
If the local codes still allow it, the easy thing would to bring in fill to bring the garage site up to the driveway height.
This will give you a chance to custom design your dirt for good drainage under the slab.
Talk to a concrete guy about what he likes as base.

That black flex gutter drain pipe will need to be lengthened to the far side of the garage.

Do you have to worry about a close neighbour on the left side of the house?
(Left as you look at it from the front.)
If so, then changing the direction of the drains to the back of your house may be the way to avoid problems.