slight slope INTO garage

[sonofagunk]

I am doing work on the house, and it looks like I have a 4" drop over 45' INTO my garage (let's assume we CAN'T change this). This is a less than a 1% drop and into the garage. So basically water will have trouble draining and when it does, it goes in the wrong direction. I am trying to find a better solution.

So I was thinking that I could have a 1% slope AWAY from the garage for the first part of the drive way, a flat part (is this even needed) and then a slope into the garage with a french drain. Will this bump be noticeable and/or annoying?

So option 1 is:
1% away from house for 29 feet, and then 4% towards for 16 feet (7.5 inch drop) where I enter the garage

option 2 is:
1% away for 23.5 feet, 10 feet flat, 11.5 feet towards at 5% (7 inch drop)

option 3 is (ok, I do not think this is an option, but what the heck):
basically I would have a large slope TOWARDS the house in the beginning, and a smaller one AWAY where it meets the house and then have a drain at the middle of the driveway where the water would collect.

Anyone have something better?

Thanks
-sog

 

[Shawn S]

Water causes major damage it sits against, or goes into, buildings. Do not slope any of it at the garage or house. Can you post a diagram of how the buildings sit on the lot?

 

[sonofagunk]

Water causes major damage it sits against, or goes into, buildings. Do not slope any of it at the garage or house. Can you post a diagram of how the buildings sit on the lot?

Yes, I know what water does, but that is what drains are for. I am not sloping towards the house, the slope is already there and nothing can be done about it, the garage is attached.
No diagram, but basically all that is needed is that the height of the sidewalk is 46' 4.7" above ground zero and the garage floor is 46' 0.6" above ground zero. I can't lower the sidewalk, and I am not lifting a house. I am trying to find a way to lessen the water that could flow in (the basement is above the local water level since the house is on a bit of a hill)

BTW, there are houses in my hood that basically have their garages underground. I do not have this, just 4" over 45'

 

[Shawn S]

It's hard to picture exactly what you have. I would recommend a slight slope away from the house, and away from the garage into a french drain, assuming you have somewhere the french drain can take the water. So you would have a dip in the driveway that would hold the french drain and give the water somewhere to go away from the buildings.

 

[Dirtydan69]

Just a little more info. Can we assume you have an asphalt or concrete driveway leading to the garage? That would make changing the slope costly. Why no just install a trough/gutter drain a couple feet out in front of you garage? You would obviously have the trench and add pipe to carry the water around and past the garage.

 

[sonofagunk]

I cant upload images at work, but it is just a basic driveway from the street to an attached garage that is common all over the USA. It is straight, 45' long (22' wide) , and has 4" drop towards the house. Nothing special. Just want to not have 990 sqft of blacktop draining towards the house

 

[sonofagunk]

Just a little more info. Can we assume you have an asphalt or concrete driveway leading to the garage? That would make changing the slope costly. Why no just install a trough/gutter drain a couple feet out in front of you garage? You would obviously have the trench and add pipe to carry the water around and past the garage.

it is straight, but because of other work, it has to be totally torn up and I have a clean site.

45' x 22' x 2" would give me 165 cu ft heading towards the house in a heavy down poor

 

[joes169]

This is exactly what trench drains (better than a French drain for this scenario) are for. The farther you set the drain from the front of the garage, the lower it's going to need to be, meaning more earth work. Also, IMPO, 1% pitch to an exterior drain is the absolute MINIMUM. 1.5% to 2% will work much better for the duration of the driveway's life.

 

[Justind97]

Does the driveway have a slight slope away from the house/garage off to the other side?

Meaning on the width, does it slope the other way?

My first thought when I read the OP was to have a trough drain at the entrance to the garage and have it lead off away from the house. This would catch any water that makes its way towards the garage.

Is there any water coming in now though? How old is the driveway?

 

[Rory Bellows]

If the drive is concrete use mud jacking. Cheap, easy, and done in about 1 hour.

 

[KMdef9]

Pitching the driveway away from the garage will not stop all of the water collecting.

IMO the garage floor needs to be addressed. Either through a drain/pump or re-leveling.

 

[Leaflessshadetree]

At my first house the road/street was higher than the garage. The house and sidewalks were along one side of the driveway and also slightly higher than the garage floor.
When I poured the driveway I made the low spot on one side about 10 ft in front of the garage. Basically the slope(s) in the driveway were triangular.
It worked out fine.

 

[sonofagunk]

basically, it is not this way yet, but it is going to be, and losing a foot off the height of the garage is not an option (4" below already and enough of a pitch to drain away from the house)

As for draining to the side, I was thinking of having it pitched so it drained left to right, but not sure if it is worth it if I still need the trench at the garage now.

I will post some pictures soon. If you look at an old post from me you will see what I am actually doing. Finally pulled the trigger and they are breaking ground as soon as the permits are finalized (and hopefully a variance is not required). But basically I am doing a "basement digout" to give me 18' ceiling in my attached garage, and then dividing it horizontally to give me 2 rooms.

 

[sonofagunk]

Currently the house has a driveway that would come up to about 2' BELOW the top of the garage door. So 5' down, puts me 4" below the side walk. Not as crazy as it sounds because there is a full basement under the rest of the house and just lowering the garage floor to be level with that. For higher end finished on the inside and inside, it will cost around $300/sqft. That is exactly what houses sell for in my town. Currently the entire front first floor of my house is garage and I basically live in the back of the house. My real estate agent says it is a break even project when it comes to resale

Outside will NOT look exactly like this (I think it looks like a monster with a bow tie)

 

[Bluedodge]

If ground hasn't been broken yet, it's an easy fix. Have the contractor bring in some fill so your house is higher than the street. If they claim they can't, build somewhere else.

 

[sonofagunk]

If ground hasn't been broken yet, it's an easy fix. Have the contractor bring in some fill so your house is higher than the street. If they claim they can't, build somewhere else.

No, the rest of the house is already there. Just changing the floor of the garage (and the driveway to match)

 

[GarageGuy89]

It's really hard to follow your explanation. A picture here would be worth a thousand words. No one really wants to go searching through your posts to try and help you out, and it's hard to give you feedback with limited info. I've read through it a couple times and every time I get something different.

Ideally...you would want to slope your driveway 1% min. for concrete, 2% min. for asphalt away from the garage for as far as you can. Period, end of discussion. Only you can decide what is going to work for a grade break, obviously a corvette is going to be more susceptible to a large grade break than if all you drive are trucks.

We also live in a world where curves exist. Any contractor worth his salt can take the edge off the steeper grade breaks in the form of a vertical curve. Something else to keep in mind.

How you collect and convey from there really depends on your ex. setup, which we know nothing about.

Sounds like you are able to raise the garage floor, you just don't want to because you want an 18' ceiling. Going to a 17.5" ceiling just solved your problem...

 

[sonofagunk]

yea, there is a picture 3 comments above your post and there is a post about it being a straight driveway is above that. Just too many comments off topic when all I cared about was slope and if people thought having an up then down slope was reasonable

 

[sonofagunk]

Sounds like you are able to raise the garage floor, you just don't want to because you want an 18' ceiling. Going to a 17.5" ceiling just solved your problem...

thanks for your reply, but the question is about slope, not whether I should have a 7.5" garage or not.

The very first line of my post says "let's assume we CAN'T change this" in regards to changing the height of the garage floor

 

[Lunker]

I think your only option is some kind of trench drain in front of the garage. I would also cut in a sump pump in the garage in case the drain fails.

 

[GarageGuy89]

thanks for your reply, but the question is about slope, not whether I should have a 7.5" garage or not.

The very first line of my post says "let's assume we CAN'T change this" in regards to changing the height of the garage floor

I did get that. All I'm getting at is, can you tell a difference between a 17.5' ceiling and an 18' ceiling?

 

[Joe Reed]

option #3 would be my choice. The driveway would slope down from the garage for a distance to a trough drain, then up from there to the street.

I'd prefer that to having the trough drain right next to the garage door. If you get a REALLY big downpour that overwhelms the trough drain (or if the drain gets clogged with leaves), you've got room for it to puddle at the low point instead of overflowing into the garage.

 

[bczygan]

My solution would be 2 trench drains. One at the midpoint of the drive, to collect all the water falling on the drive from the street to that point.

A second one right at the garage would collect water falling on the rest of the drive.

Both would be of a large enough capacity to handle a 100 year storm for the entire drive.

Better than tearing up the whole drive to redo it. Just 2 trenches.

Bill

 

[Lunker]

My solution would be 2 trench drains. One at the midpoint of the drive, to collect all the water falling on the drive from the street to that point.

A second one right at the garage would collect water falling on the rest of the drive.

Both would be of a large enough capacity to handle a 100 year storm for the entire drive.

Better than tearing up the whole drive to redo it. Just 2 trenches.

Bill

That's a good idea

 

[YeahPete]

Those garages will never keep the water out. Sounds like water from the sidewalks and streets will come pouring in. Don't fight nature. Seal off the garage with concrete and fill dirt, and build another garage somewhere else. I mean think logically where are you going to send all that water? You think you can pump water faster than it rains? Think again. Imagine 6" inches of rain, then measure up that entire area that flows to the garage include roof and gutter. Lets pretend 100'x200'x6" = 10,000 cubic feet of water. Don't get me started on retaining walls which nobody ever builds right either. Don't fight nature. Good luck and Happy Thanksgiving.

 

[Steevo]

I am assuming that the lot continues to slope rearward, allowing drainage to be routed down the side of the house to the rear of the yard.
I had a house with a similar setup, but with much steeper slope from street towards house, and the driveway in front of the garage was sloped enough that I wouldn't jack up a vehicle out there.
That said, the sloping driveway ran directly towards the 3-car garage, with enough surface area to collect a LOT of water in a heavy downpour. The apron in front of the garage doors was at most 3' of slope away from the doors, with a trough drain that met the two slopes at the lowest point. The trough drain was 6" wide x 6" deep, with slotted covers, and ran the full length across the front of the driveway (35'). The trough sloped slightly to the side of the house, directing all of the flow that way, where a buried drain pipe ran to the back of the lot. In the worst of storms, the water would exceed the capacity of the drain pipe, and water would flow on the surface down the side of the yard, which was graded to accommodate this flow with about 3' wide "V" that guided the flow safely out the back.
Even in the heaviest of storms, I never once had water overrun the driveway trough drain by enough to get into the garage, despite only about 4" of rise, and only 3' of driveway apron between the trough and the garage doors.

 

[ford33]

I owned a home like you showed in your drawing. A split level with the garage floor below the sidewalk and street level.

After a couple years, I didn't like the home. Water intrusion in the lower level was a concern and sometimes an issue. In the future, I will never own a home were the lower living area is below grade. Basements excluded.

In the home I mentioned, we had a single 12" diameter round drain with metal grate located in front of the garage door. The concrete in front of the garage door sloped towards the drain. The drain was connected to the street sewer system. All per code with the city when the house was built in the 1960s.

Eventually, the drain system piping became clogged with leaves and dirt and would not drain water adequately. Came home one day after a heavy rain with about 1 inch of standing water in the garage.

Our solution was to have the drain piping cleaned of 40 years of dirt and gunk and then we installed an 18" drain grate cover with smaller openings to prevent leaves from entering the piping. From that point on I had to remove the grate every year to clean out the dirt and rodents which collected at the bottom of the drain pipe. Keeping that drain grate clear was a weekly occurrence. Another reason to not like that style of house.

OP, your solution to install a drain in front of the garage will work. I would not recommend multiple drains as one is sufficient. But provide a means to allow plenty of water flow to either a sewer or drain field. I would not count on a sump pump working with all the dirt and rodents moving through the pump. Finally, provide a method to easily clean out the drain. You will be surprised what falls into a driveway drain. Think, car keys.

Good luck.

 

[apollo11]

My solution would be 2 trench drains. One at the midpoint of the drive, to collect all the water falling on the drive from the street to that point.

A second one right at the garage would collect water falling on the rest of the drive.

Both would be of a large enough capacity to handle a 100 year storm for the entire drive.

Better than tearing up the whole drive to redo it. Just 2 trenches.

Bill

^^^^^ this

 

[joes169]

yea, there is a picture 3 comments above your post and there is a post about it being a straight driveway is above that. Just too many comments off topic when all I cared about was slope and if people thought having an up then down slope was reasonable

On the plus side, all of the opinion (and confusion) you're getting here is free. The downside, is even at that meager price, most (not all, a few posters actually understand what you're trying to do) of it still isn't worth what you're paying for it. You need to discriminate between the good & the useless info yourself, but I assume it's not to hard!

Don't be discouraged though, this kind of thing is done all of the time. Underground parking garages rely solely on this method of water management, and last I checked, they're still building them every day.

As I stated earlier, you need a trench drain outside of the garage (don't even think about draining the water inside to the garage, as I believe someone else may have suggested! ) at a few inches lower than the garage floor. You're going to need to source a a decent modular trench drain that has a sloped bottom and decent capacity for the heaviest of rains. The cheap 4" by 6" drains found at the big box stores aren't adequate for the potential water flow. The nicest ones I've used are a combination of concrete and polymer, have a sloped bottom, and would range from about 6" deep to 9" deep on the outlet side fora driveway your size. Expect to pay about $75-100 per lineal foot for a good trench drain, materials only.

Once you figure out the drain itself, you have to figure out where you're going to dump it. The three most common options I generally see are the city storm sewer (if it's close, and the muni allows the connection), daylight on your own property (like possibly your back yard, if the grade drops off enough?), or an interior sump crock with pump. The crock & pump would be my last choice, as it's the least dependable, takes up valuable floor space, and is the most likely to leave your garage wet one day.

Best of luck.

 

[Platonic Solid]

 

[joes169]

Post 15 has the conceptual image. I'm not sure how the OP can include a picture of the actual situation, as it's not built yet...........

 

[Platonic Solid]

joes169 - A current pic would certainly help visualize the potential.

 

[firebirdparts]

I don't follow you at all, but I would say slope whatever so that water flows away from the garage and doesn't collect anywhere and goes downhill somewhere. does this require a trench drain? maybe. The driveway will have to be configured to get water off the low spot somehow (you pick)

Naturally people have street level above their garage level all the time. you just come down to a low point in the driveway and then back up into the garage.

My advice is never omit the part about "back up into the garage".

If the driveway in question is already finished, then I just didn't pick up on that.

 

[bczygan]

There are formulas you can use to calculate flow rates and capacities so you can size and locate drainage methods.

Commercial properties many times need to maintain water on site in retention ponds when they develop the site. To size them you need to calculate the flow of water across the site before and after hard surfaces of buildings and paving are installed.

If the topography allows, a swale can carry the water away on the surface.

But you do still have to keep the trench drains cleaned out.

Bill

 

[NUTTSGT]

I guess, I'm in the boat of those that don't quite understand what the OP has or wants.

A picture would be nice so we can actually see what he has or what he wants. He attached a drawing but also mentions Outside will NOT look exactly like this.

He also states he has a 4" drop over 45' INTO my garage but that attached drawing is way more than what he says.

Is the intent to make a garage out of the basement ? Anybody else having trouble following the OP ?