New 30 x 40 garage

[blake616]

I am planning to build a new 30' x 40" garage in the spring. Due to the lay of my land, this garage will be built into a hill. I anticipate the back wall and a portion of the east side will need to be a poured concrete wall. The remainder of the garage will be standard 2 x 4 construction. Just wondering if anyone has experience with this type of garage and has any suggestions or advice?

 

[landlord30]

I do not, the first thing that comes to mind is exterior waterproofing and good drainage. Sorry I can't offer more.

***please put your location in your profile so others can better assist you.

Welcome to the board!

 

[matt_i]

Definitely I would waterproof (like a basement) any concrete sidewalls above the slab that sit permanently under grade.

Definitely I would carefully plan stormwater management so that there is a lower spot than the intersection of the concrete wall and the cut hillside. In other words, top soil or sod should go down from the concrete wall for a short ways before going back up to meet the hill. Don't press the wall into river dam service.

 

[aptdweller]

I don't know what the usual building practices are around you, but I will echo the train of paying close attention to the waterproofing.

Were this my build, I would use a geotextile wrapped footing drain (run to daylight) with lots of 3/4 gravel on top, with a 2 part waterproofing layer (bituminous coating with dimple board). Don't forget foam insulation and a capillary break (vapour barrier) under your slab.

For more information that you will ever need:

http://buildingscience.com/documents/digests/bsd-103-understanding-basements

Done right, water will never be an issue for you.

 

[SgtHawkUSMC]

Definitely I would waterproof (like a basement) any concrete sidewalls above the slab that sit permanently under grade.

Definitely I would carefully plan stormwater management so that there is a lower spot than the intersection of the concrete wall and the cut hillside. In other words, top soil or sod should go down from the concrete wall for a short ways before going back up to meet the hill. Don't press the wall into river dam service.

Especially in SE Michigan. We have a VERY high water table and a lot of clay. Can you cut deeper into the hillside so you don't have to have dirt right up against the wall?

 

[Randy in Maine]

In some states you are allowed to use 2" tire chips between the hill and the concrete wall of the garage. I usually suggest about a 3-5' wide layer of tire chips wrapped in a geotextile fabric and with a PVC drain to keep this area well drained and to reduce the nature pressure of the hill trying to push over the garage. The tire chips drain well, weigh a lot less than soil, and do not retain any water.

Check with your state environmental agency to see if that is possible to do where you are located.

 

[ryan77]

I just built one, basically you are digging a basement, use "form a drain" for the footer form, rubberseal the outside wall( I also used dimple drain board over the rubber) throw an extra perforated tile in the bottom and run downhill to daylight, and backfill all the way up with gravel for drainage, and burm a few feet away around the hill to divert rain water from coming down the hill and up against the wall, whatever you do drainage, drainage, drainage, I have a spring in the hill I built into so my drains trickle all the time and everything has been good so far, give the water someplace to go

 

[marksland]

I built the same size garage in very similar conditions, check out my build thread and if you have any questions, feel free to ask.....

 

[bjcouche]

I have some firsthand experience with this as well. My building is a 40x64x14. My back wall is cut into a hill and inside the shop, the concrete wall is 8' high. Because my wall is this high only on 1 side it's basically more like a concrete retaining wall than a basement. A basement wall has floor joists spanning to the other wall, preventing it from caving in. It would be helpful to know just how high of a wall you will be needing. Also, I have a few recommendations because hindsight is 20-20...

Have your site accurately measured with a laser level by someone who knows what they are doing. This will start you with an idea of how tall the wall will be. Then add to that wall 1' to get the wall above grade (you can't have your wood sitting on the wall 1" from the ground) Then add another 8-10" so that you can slope the ground away from the building. You want to slope the ground away from the building a certain distance according to code. Assuming you are building into a hill, the negative slope away from the building will meet the positive slope of the hill. At this point you can place a french drain, but I'd also recommend a shallow ditch around the building. The ditch would force surface water running down the hill, to route in the ditch and around the building, instead of through it, or potentially overloading the foundation drain... As others have said you'll also need a foundation drain.
After teh concrete is poured, have the exterrior sealed with whatever they seal basements with in your area. Then have them install rigid foam on the outside of the concrete before they back fill. The foam is cheap, and if you ever want to heat or cool your shop in the future, now is the time to insulate it from the outside which is way better than the inside.

Finally, make sure your contractor or engineering firm is familiar with this type of construction. For this type of build, I would insist on stamped prints even if the city or county didn't require them. That way there's the possibility that someone with an engineering degree actually looked at the design.

One final thought.... If you don't absolutely HAVE to build into a hill then don't. It will look good but will increase your build cost substantially. Mine more than doubled due to the added concrete.

Brian

 

[chaosracing]

I know someone that did a similar project. Water control and water proofing are a must. Also make sure you check with an engineer. He had to have 6' wide footers poured just to help hold the wall from being pushed by the soil.

You also want to insulate the exterior as well.