Driveway grade question

[DOHC427]

Hello,

I’m building a building with a wide door on the gable end.

My property has a slight corner to corner slope to it and there is approximately 18” difference from the far right rear corner (highest spot) to the opposite front left corner (lowest spot). The door is on the lower gable end.

The dirt contractor brought in 8 loads of dirt and built up a level pad and then put form boards around it so it could be re-surveyed to make sure it is in the right spot.

The issue is that I’m concerned that the driveway grade will be too steep.
It is going to have to rise about 20” in 25 feet. Does this sound steep?
What is an ideal driveway grade? My cars are fairly low and I’m concerned that they will have trouble getting into the garage without dragging.

 

[RVDan]

A quick look at my driveway is about 18" over 32 feet and doesn't feel at all steep.

 

[Blazinzuk]

I think 1" per foot = an 8% grade. Sounds steep but not really. Definitely steep enough to warrant functional parking brakes if you park on it.

It is possible to make transitions. Not one grade but less steep for the first several feet and the last several feet.

IMHO ideal driveway grade is slightly sloping away from the shop or garage door.

 

[cvairwerks]

The longer the transition, the better. Short, steeper approaches tend to cause you to bottom out trailers or loaded trucks. I’ve seen short approaches that will cause a trailer to hang up and lift one or more wheels off the ground. This usually results in damaging both the trailer and the driveway.

 

[Ole Slewfoot]

You must live in one of the less hill abled regions.

 

[larry4406]

20" rise = 1.67' rise.

Rise over run is slope, so 1.67/25*100 = 6.7% slope. For perspective, if your driveway were 100' long, it would rise 6.7'.

For minimum overlot drainage, civil engineers want 2% as a minimum.

In new construction, the driveways on my homes have ranged from 3% to 13%.

Conclusion, not steep at all.

Give some thought to your slab's garage door weatherlip detail. I prefer the garage slab to slope down in this region to receive the garage door weatherstrip vs the pan-type depression one sees commonly in residential construction. The slope detail readily allows rolling jacks to slide across the opening and no trip hazard.

 

[NUTTSGT]

How far were you when you took that picture ? Any reason the driveway can't come back that far, it looks farther than 25'.

 

[DOHC427]

20" rise = 1.67' rise.

Rise over run is slope, so 1.67/25*100 = 6.7% slope. For perspective, if your driveway were 100' long, it would rise 6.7'.

For minimum overlot drainage, civil engineers want 2% as a minimum.

In new construction, the driveways on my homes have ranged from 3% to 13%.

Conclusion, not steep at all.

Give some thought to your slab's garage door weatherlip detail. I prefer the garage slab to slope down in this region to receive the garage door weatherstrip vs the pan-type depression one sees commonly in residential construction. The slope detail readily allows rolling jacks to slide across the opening and no trip hazard.

Do you have a photo of the type of weatherlip you are talking about?
Sounds like a good idea.

 

[DOHC427]

How far were you when you took that picture ? Any reason the driveway can't come back that far, it looks farther than 25'.

I have quite a distance available but about 30 feet in front of the building is where a bit of water drains from right to left across my property. This is only when it rains extremely heavily. My original idea was to just do a very slight dip across the concrete.
I could make a gradual slope to the building for 50 feet or more but I would need to put some kind of drain tunnel through it.

 

[DOHC427]

This is my first time to build and I want it right. I will have a classic car or two in the garage and don’t want a problem with scraping the bottoms of the cars.

 

[ConCretin]

My question is this. Is the concrete on the left side of the picture going to be thickened all the way down to the existing grade? That would probably be OK but a little unorthodox. If he plans on bringing the sub grade up to match the rest, he should have done it before he put up forms. No way he'll get adequate compaction working around the formwork.

 

[DOHC427]

Here it is today. They trenched it for 30” deep perimeter and cross beams.

I set a ladder set at 20’ show potential grade.

 

[larry4406]

Do you have a photo of the type of weatherlip you are talking about?
Sounds like a good idea.

Attached is a picture showing the sloped/tapered section of the garage slab at the garage door. My build had stem walls and the garage slab was poured after the structure was up.

Check out this thread for more details.
https://www.garagejournal.com/forum/showthread.php?t=237592

 

[ConCretin]

Here it is today. They trenched it for 30” deep perimeter and cross beams.

I set a ladder set at 20’ show potential grade.

So they are placing the perimeter 'beams' and the slab all at once? Or are they going to place the beams and come back to do the slab? Just curious.

I don't think the grade of your approach will pose any problems.

 

[Monteman]

Are you adding a lift or think you might at any time in the future? I have that problem now where the slope into the garage is slightly too much and some of the lower cars high center when going up the ramps to the top of the lift. I have to use boards and such to get them on there. If you think you'll have a lift then you may want to compensate for that.

 

[Vintage Veloce]

How to calculate breakover clearance.
http://www.vintageveloce.com/2016/05/calculating-driveway-to-garage.html

 

[kbs2244]

Just avoid this

 

[Hilltopmasonry]

Just avoid this

That’s good though since the water runs off and doesn’t ever puddle up


Sent from my iPhone using Tapatalk

 

[rburke65]

I don’t think that would be an excessive incline.

 

[DOHC427]

we put a gentle slope in the approach.
Looks like it will lower the door opening a few inches and make the transition
pretty smooth. I think I like this.

Then we will put a slight slope on the apron and extend the driveway with a flat area and make the slope as gentle as possible.

See anything wrong with this plan? Any suggestions?

 

[mgbbob]

I recently purchased a 4 post hoist and hauled it into the garage on a car hauler. The tounge of the trailer just barely scraped coming in. My driveway is pretty flat. Maybe 4" of fall in 14'. You might want to consider that issue if you plan on backing a trailer into the shop.

 

[mgbbob]

Another option that we used in road construction when tying in driveways is to break the slope a bit in the middle or even a couple of spots. Sort of roll in in. That might help.

 

[Vintage Veloce]

Is the rest of the garage floor level or sloped? If the floor is level, a little bevel at the opening like this is good for when it rains. But beware of the garage door fit: it needs a flat surface and may overlap a little on the inside: the door may be an inch or more wider than the opening.

Edit:
Looking at your picture again, I would add some wood to make that bevel extend around the corner inside the door opening, to allow the garage door to be up to 1.5" wider than the opening, but to still have a flat surface for the bottom of the door. Does this make sense? Don't expect the door's bottom gasket to make up for this.

 

[Vintage Veloce]

Visually, from the ladder shot, the breakover doesn't look too bad... but it depends on your cars. You really only get one chance to do this "right". I wanted cars with less than 4" of clearance to be able to enter and exit my garages. My wife's volvo is that low, if you are thinking Porsches or race cars or exotic cars someday you want even less. So I did the calculation, it's not hard. See my diagram earlier in the thread.
Heck if you need to, just cut out a profile of your lowest car in a piece of plywood and use it as a profile gauge for the breakover. Mark out the wheelbase on the plywood and cut a notch between the marks that is as deep as your lowest car's ground clearance.

 

[LXCam]

The angle and breakover isn't going to be an issue IMO. But I would suggest you reconsider having the run-off go over the concrete even if you create a swale to channel it. It wouldn't cost much to do a couple 4" or 6" lines under the driveway and flow the runoff into a headway on the uphill side.

The reason I suggest this is my front yard flows three acre's across it in heavy rains. I dealt with the mess for many years until I poured a new driveway. At that time I redid all the drainage for the entire property to stop that mess from getting tracked everywhere. I used a couple 6" corrugated flex lines and a headwall and that solved the problem up front.

In the rear in front of what is now my shop I had graded that area to flow around the backside which worked great until my neighbor regraded his lot (intentionally) so that the flow goes right in front of my roll up door. It's a flipping mess after a major storm. One of these days I'll saw cut out a section and install a French drain to stop this which also might be a consideration for you.

 

[kbs2244]

If he has a good local reputation,
he is the voice of experience.

From this far away, it sounds like a good idea.

 

[LifeLongWNYer]

Thanks for that formula, Vintage Veloce. It will come in handy when i start working on my elevations.



.

 

[yeldogt]

I always do the slope in the apron -- water flows away and the outward angle keeps water from splashing on the door. I also do a small curb at the garage slab/ apron joint and have the door come down on the apron. This keeps the edge of the slab inside the heated area. I don't find the lip to be an issue -- keeps leaves and other **** form being blown into the garage.

 

[cj7jeep81]

I think the grade will be fine as well. My trailer deck is a little taller than that, and tried to load a relative's lowered car onto it. 8' ramps were just a little bit too steep to get it up without dragging. 25' would be 1/3 the slope, so would clear no problem.