Garage slab exit flush with out side grade?

[Gunslinger99]

Hello everyone,

Very new to this forum as this is my first post. From what I have read so far this forum seems to be a great source of information. So I am hoping someone may help me with this issue.

We are getting ready to build a new home, we are still finalizing the plans with the architect but have a problem I can't seem to find a resolution to.

So here is the problem:

Because of the nature of the lot we are doing a full daylight basement. This works out great because it makes a lot more sense to do the suspended slab over the garage rather then fill it in with gravel. And that made the approval process a lot easier. The issue we are having is I'd like to put an automobile lift in the garage under the suspended slab. The ceiling is 9' but the lift is 12'1" so we will need to drop the floor about 3 1/2'. No problem with that. The problem is the wife doesn't like the looks of dropping the garage entry that far down from the rest of the house. So my thought was ok maybe I could split the difference between the outside and inside. Meaning the outside would drop 1' and the inside 2.5', or outside 1.5' and inside 2' or something like that. She's ok with a foot or two drop on the outside but any more then that is a no deal. I would then pour a concrete ramp inside the garage to allow cars to drive down the ramp and into and out of the garage.

Ok, so down to my real question. Does the slab inside the garage have to meet the grade on the outside of the house. I know the slab should be sloped to the outside, but I have also seen garages with a drain in the center and the floor slopes to the drain. So I am almost thinking I could install a drain and this could probably solve my problem???

Hopefully I am making some kind of sense and more importantly I am hoping someone could help me figure out a solution to this 'problem'.

Thanks in advance to any suggestions, recommendations and opinions. And I am sure I will be posting again as we go through this build.
T.

 

[larry4406]

Water is your enemy, gravity is your friend. I would not make the garage intentionally a low point for the sake of a lift. You will regret this on every rain and snow event.

Keep the garage apron slightly higher than grade, and pitch the slab slightly towards the garage door. Changing the ceiling from 9' to 10' for the first floor would seem to help your situation. Step the foundation, making the main level higher than the garage (done all the time), but you wind up adding steps and possibly a stoop at the front door. What is above the garage - a room or dead rafter space?

 

[rasit]

So here is the problem:

The issue we are having is I'd like to put an automobile lift in the garage under the suspended slab. The problem is the wife doesn't like the looks of dropping the garage entry that far down from the rest of the house. She's ok with a foot or two drop on the outside but any more then that is a no deal.

The problem seems clear to me, and I sympathize with you.

Larry gives sound advice about "Water is your enemy, gravity is your friend." If the grade is sloped towards the garage you might consider a trench drain across the front of the door opening. These are open grate, about 4" wide X as long as you need. You may be able to tie your roof drains into this system to carry water away from the structure. If you have to ramp down to a sunken garage, a floor drain system is definitly in order.

 

[noslo04]

A driveway sloping down to the garage is a bad design. I would not even remotely consider doing so.

More details on the house are needed to develop a solution. Is the house a split-level/split-foyer or is it a typical one- or two story house with basement? Is the garage a front-load, meaning the driveway and garage door are at the front of the house? What does the proposed grading look like? Is the house higher than the street?

Larry definitely knows what he is talking about. Generally, the garage floor will be 1.75' lower than the first floor (3 steps), so the grading around the house will work correctly and to keep driveway from being excessively steep. Specify 4 steps (~2.5' garage-to-first floor) and a 10' first floor ceiling height and you will have room for your lift. Be prepared to pay for those 10' ceilings however.

 

[Gunslinger99]

Water is your enemy, gravity is your friend. I would not make the garage intentionally a low point for the sake of a lift. You will regret this on every rain and snow event.

Keep the garage apron slightly higher than grade, and pitch the slab slightly towards the garage door. Changing the ceiling from 9' to 10' for the first floor would seem to help your situation. Step the foundation, making the main level higher than the garage (done all the time), but you wind up adding steps and possibly a stoop at the front door. What is above the garage - a room or dead rafter space?

There a bonus room above the garage. It's not tall enough for living space so we were going to use it for storage. This could possible be changed but the wife has already hooked on the idea of using it for storing Christmas items. So, that may prove difficult to change......

 

[Gunslinger99]

The problem seems clear to me, and I sympathize with you.

Larry gives sound advice about "Water is your enemy, gravity is your friend." If the grade is sloped towards the garage you might consider a trench drain across the front of the door opening. These are open grate, about 4" wide X as long as you need. You may be able to tie your roof drains into this system to carry water away from the structure. If you have to ramp down to a sunken garage, a floor drain system is definitly in order.

Thanks! I had considered the trench drain in front of the garage and am glad you mentioned it too. Helps me realize I am not entirely crazy as my wife tends to hint that I may be. She thinks the idea of a lift is pretty far out there. Tried to explain 'it's just another tool' but to no avail, however she did soften up a little bit about dropping the entrance a foot or two. Of course I haven't mentioned the water drainage issue yet......

 

[Gunslinger99]

A driveway sloping down to the garage is a bad design. I would not even remotely consider doing so.

More details on the house are needed to develop a solution. Is the house a split-level/split-foyer or is it a typical one- or two story house with basement? Is the garage a front-load, meaning the driveway and garage door are at the front of the house? What does the proposed grading look like? Is the house higher than the street?

Larry definitely knows what he is talking about. Generally, the garage floor will be 1.75' lower than the first floor (3 steps), so the grading around the house will work correctly and to keep driveway from being excessively steep. Specify 4 steps (~2.5' garage-to-first floor) and a 10' first floor ceiling height and you will have room for your lift. Be prepared to pay for those 10' ceilings however.

It's a fairly typical ranch/rambler style home. Great room/dining room area is vaulted, 9' ceilings everywhere else including basement. The garage is a front -load but the garage in question is at the rear of the house under the suspended slab. It's a unique lot as the DOT used the dirt to build the freeway many years ago and is flat but drops down about 20' to where we are going to build. Luckily we have almost 2 acres to work with and about 200' of frontage to make a very gradual slopping driveway. It will be a long driveway but the slope shouldn't be bad. But to answer your question the majority of the house will be below street level. The first floor garage slab will be about 10' high from where the grade is now so the driveway will start at about 20' and slope down to about 10'.

I'm not sure if 10' ceilings would solve the problem as the county we are building in has a 32' max height and we are already there. Going to 10' ceilings could be done but would flatten the roof more and we are already at a 6/12 pitch.

 

[Gunslinger99]

What if I kept the outside entry at the same level as the outside grade but built a ramp inside? If I dropped the garage floor 3.5' on the inside how long will this ramp have to be? And would this really be a good idea? Probably take too much level space?

The total size of the garage is 24' wide by 35' deep.

Thanks.

 

[Frogday]

I just went through a similar situation with an addition to my house. I wanted 10' ceilings under the addition for a lift. The best way to do this was to put a ramp inside my garage that drops the floor by about 16". My ceiling in the garage was all at 8' 8". The lower area is forward of the 3rd bay in the garage.

Getting the ramp passed by the inspector wasn't exactly easy. He was trying to get the ramp to conform to handicap ramp codes (1/12 pitch). It wasn't until everything was finally finished that the inspector gave in and passed everything. My rap ended up being about 9' long to drop 16". I would recommend checking the building codes in your area. You may find that going down 3.5' will make for a very long ramp.

The other thing to consider with the ramp is the ground clearance of your car. I'm stacking Corvettes and found that I can drive all but a slightly lowered C5 over the hump without high centering. I'll have to use some boards to help it over the high point.

 

[PassnThru]

I think your situation is begging for a detached garage to be built also. If you are not in a neighborhood with restrictive bylawsand you have the land then you could add a detached garage in the height that you need. Yes - more money but maybe better in the long run than trying to adapt your house design to a lift?

 

[Gunslinger99]

You may be exactly right on that. I just learned that the ceiling height in the garage underneath the suspended slab is going to be about 7.5'. I was unaware of that when I first posted. The basement will have 9' ceilings but the drop from the main floor to the top of the garage slab is 18" then there will be about 4" of concrete topping on top of the 8" precast forms. However I can put the slab for the underneath garage flush with the footings and get back that 4" and there is a way to install the forms so they are flush with the foundation and get back that 8". So still 7.5'. I may need to figure something out. That just seems like it will be too closed in, and have a cave like feeling to it????

I really don't like the idea of dropping down anymore as the door will then drop below finished grade and as others have mentioned rain and melting snow has the potential to become a big problem. But it may be my only solution.

If I decide to drop the floor down a couple of feet and drop the door down a couple of feet as well so the inside garage floor and outside grade are at the same level, is there anything else I can do besides a trench drain to keep the water from flowing into the garage? Maybe a couple of trench drains? I can see how this could become a real problem especially if/when a huge rain storm could fill up the drains faster then they can expel the water.....

hmmmmmmmmmmm.............what to do.............................?