Advice Needed on Building Retaining Wall Next to Wood-frame Garage

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Old 03-14-13, 08:14 PM
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Advice Needed on Building Retaining Wall Next to Wood-frame Garage

I have a wood-frame on-slab garage built in 1940 in Baton Rouge, Louisiana. In the past a utility right-of-way was built up of dirt and gravel a few feet behind the garage, which resulted in the grade of the right-of-way being about 3 feet above the grade of the garage floor. The edge of the right-of-way slopes down to the bottom of the rear garage wall.

Problem: Whenever it rains, water drains through the garage.

My plan: I plan on building a concrete retaining wall against the exterior rear wall of the garage and fill in the void between it and the right-of-way so that water drains away from the garage.

Questions:
1. Where can I find instructions for building a retaining wall for this purpose?
2. Since the garage is unconditioned, what sort of water barrier do I need to incorporate into the retaining wall to keep moisture coming through to the inside wall of the garage?
 
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Old 03-15-13, 06:12 AM
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Welcome to the forums!

You 'll need to dig down and pour a footer to lay the block on. Usually the back/dirt side of the block is stuccoed and then sealed with foundation tar. It's also a good idea to install a perforated drain tile and gravel to collect any water and pipe it out to daylight.

How do you intend to address the gap between the block and the garage wall?
 
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Old 03-15-13, 07:27 AM
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I don't think you want to consider making a waterproof retaining wall. That complicates construction considerably but you will get most of the benefit you want with a traditional retaining wall and getting the ground above the wall to slope away from your garage.

I have good luck with Keystone brand retaining walls though there are other similar systems on the market. It's a commercial grade, dry stack retaining wall so the blocks are much bigger & heavier than what you'd find at your local home center but then it's also much more durable and structural. Best of all it does not require forming or pouring concrete or mortaring blocks so it's easy to do the work in stages and can be done without equipment if you are up to driving a shovel. Here is the installation manual:
http://www.keystonewalls.com/media/C...stallation.pdf
 
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Old 03-15-13, 04:48 PM
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Thanks for the suggestions! Right now I intend to butt the retaining wall against the garage wall, maybe replacing the existing wood siding with fiber-cement siding where the retaining wall would touch the garage. Also, I plan to install flashing under the first row of siding board directly above the top of the block wall.

Is this a good idea?

Also, should I put a vapor barrier on the garage side of the block? I don't want my garage wall to rot.
 
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Old 03-16-13, 05:38 AM
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Installing plastic between the cement board and the garage framing would be a good idea although I like PD's suggestion of erecting a wall a few feet back from the garage. Might mean more digging but it doesn't modify your structure any.
 
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Old 03-16-13, 11:05 AM
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Unfortunately, I don't have enough room between the garage and the right-of-way to build the wall much farther than maybe a foot or so from the garage. Then I would have to contend with keeping that gap clean of leaves and such.

After reading your suggestions, I'm considering constructing the wall as follows: existing garage wall > fiber-cement siding > plastic vapor barrier > cinder blocks on footing > foundation tar coating > perferated drain tile on gravel > fill-dirt sloping away from garage

Do you see problems with that approach, given existing conditions?
 
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Old 03-16-13, 11:40 AM
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The plastic vapor barrier goes behind the siding. I don't know that you would need siding behind the block. It's usually best to stucco the block prior to applying the foundation tar, that fills all the little voids in the block. The same mortar mix you cement the block together with can be used for the stucco.
 
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Old 03-17-13, 08:43 PM
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Thanks for the tips! This is a great site and your responses really helped!
 
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Old 03-18-13, 12:06 PM
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Concrete blocks instead of cinder blocks would result in a stronger wall. Much heavier and less likely to move.
 
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