Garage Elevation Choices

[danmor]

Hi!

I'd like to know the pros and cons of different garage slab elevation choices. I have a sloped lot whose average grade is 25%. Plan to make a 1/4 circle drive entering from the top right corner. Proposed garage corners for my 35x28 garage as shown on the sketches. The lot contour sketch has rough contours drawn every two feet with zero at the lower house foundation wall (walk out basement). What elevation would be best for the garage slab and house basement slab? Here's what has come to mind in choosing these locations.

1. The best view location for the house places it's lower wall ~80 from the top/entry of the lot. It could move a few feet up, but no further down (has to be at least 100' from a cliff) and a few feet to the left. Don't want to place it closer than 10' from the property line to allow a short Y turn area between the house and the line when backing out of the garage, so it can't move more to the right.

2. I don't want more than a 2' elevation difference between the garage floor and house. I will have a covered/insulated breezeway connecting the two buildings.

3. There is a view to the bottom so the house can't block the garage/apartment.

4. There also needs to be at least 6' between the house and garage for a house entry porch, not shown in the diagram.

As shown, the garage slab would be 2' above grade on one side, 8' below on the other leaving a 2' drop through the breezeway to the house. As shown the house is grade at the lower side, but I could elevate it a couple feet.

Thanks,
Dan

 

[joe_padavano]

I had a similar concern when I built my shop. I elevated the slab as much as possible to avoid a problem with water coming down the hill.

 

[MetalBuildingFun]

I had a similar concern when I built my shop. I elevated the slab as much as possible to avoid a problem with water coming down the hill.

^^^^^^^^This^^^^^^^

If the concrete guys had done what I asked them to do I wouldn't have the water issues I have with my project. You really need to factor in that rain water coming down and flooding at the back of your building. Also, add in the proper drainage too, it will help to keep your area from flooding.

 

[kbs2244]

This is where an experienced design landscaper earns his money

 

[Vintage Veloce]

Imagine torrential rain.
Look up 100 year storm rainfall for your location.
Calculate all the water that can fall per minute on the lot and any area that runs onto it.
Make sure your drainage can support that without anything being flooded.
Really, that is what is necessary.

 

[Vintage Veloce]

More info here: https://www.wsdot.wa.gov/publications/manuals/fulltext/M23-03/M23-03.04Complete.pdf

 

[danmor]

Thanks for the ideas

 

[Jking24]

Whatever your guestimating add 6"to 12" you can always build the area around it up but if it's to low its a much bigger problem

 

[Joemctag]

Agree with Vintage. Build for a torrential rain and also for, say, four days of slow, steady rain that will saturate deep no matter how your surface is graded.