Retaining wall to support driveway expansion

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Old 09-30-13, 05:51 PM
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Retaining wall to support driveway expansion

So this is my first post here but I have the feeling that I will probably be around more frequently.

My issue:
My wife and I want to expand our driveway a little bit since it can be a bit troublesome to get in and out of the garage if there is even 1 car in the driveway. Our house is built on a hillside and our driveway traverses across the hill to get up to the elevation of the garage. So what we'd like to do is build a retaining wall to expand part of the driveway so that there is essentially a parking spot that doesn't interfere with the normal comings and goings of our house.

This image is a side view where the driveway is on the left. We want to get the driveway out to as far as the aspen tree in the foreground on the right. That horizontal distance is about 11.5 ft. Height to driveway level is about 6.25 ft.
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This image is looking down the hill from the edge of the driveway. Again you can see the aspen tree that is our goal.
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This is the reverse of the first image just to see more I suppose.
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This may be the most helpful image. We would like to go from the aspen tree(s) on the left, all the way to the ponderosa pine on the right where the wall would likely need to make a curve or turn I would imagine. Also you can kind of see a slight leveling out of the hillside that goes approx from the aspens to the ponderosa. I'm not sure how much that would work to my advantage.
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My biggest concern when doing the research is that many retaining walls have a base that is on level ground. I don't have that. I am looking to do most of this myself and am quite capable. I'm just not particularly experienced with this sort of engineering. I imagine that I would need to be using some sort of anchor that goes back into the hillside and I can imagine that for timbers but not sure how that would work for blocks. If it seems like too much engineering for me I'm not entirely opposed to having a company do the engineering but me doing the work. Saving money and getting into better shape is a goal here also. Thanks for any helpful input anyone is able to provide.

Nathan
 
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Old 09-30-13, 08:56 PM
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Welcome to the forum.

Your local AHJ may require that you get an engineer involved to design your retaining wall (including a stamped set of drawings, to submit with your building permit application), so you might want to touch base with them first, before getting too far along on the project.

Although it's not real clear from the photos, I suspect an Allan Block wall or something similar would work well. Done properly, such a wall could both enhance your property's appearance and value, while accommodating your parking concerns. Elevation differences can be dealt with by using stepped construction, either for just the top portions or for the entire wall, starting at the base course construction. I'd incorporate a matching paver step system into the wall, if a vehicle is going to be regularly parked below it, for easier access to the house. One of the positives of such a wall is that no concrete footings will be required.
 
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Old 09-30-13, 11:25 PM
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Oh I'm not getting anywhere with this project for now. This is pretty much all investigative research.

Been trying to figure out the AHJ acronym. I assume it has something to do with the building dept at my local county office?

I'm hoping that the small, sort of leveled area that I mentioned in the last photo would be enough to support the wall without having to terrace a wall all the way up from the drainage at the road, (which may not even be allowed by the county for all I know). The driveway is at the top of the hill there. There is no parking on the side of the road at the bottom of the hill so I would have no need for a paver step system (assuming I understood your meaning correctly).

I may not have been clear enough. Perhaps I will make a crude drawing to see if that clears things up.

I have been leaning towards the idea of contacting someone to do some engineering. However I don't want to waste anyone's time so depending on how much doing the engineering on something like this would cost, (together with the build cost [my labor or theirs]) I don't know if it would be currently a viable option. But perhaps they could at least take a quick look and give me basic ideas of what is feasible without much upfront costs?

Nathan
 
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Old 09-30-13, 11:54 PM
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AHJ = Authority Having Jurisdiction. In other words, your building permit people. Either local, county or state, depending on what pertains in your area.

You really need to contact them before doing anything else, as I mentioned earlier. With a few pix and a rough sketch, they will send you in the right direction on your path forward.
 
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Old 10-01-13, 04:43 AM
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My biggest concern when doing the research is that many retaining walls have a base that is on level ground
You dig out the footer/base until it's level. You can stair step it if need be.
 
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Old 10-01-13, 06:44 AM
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Here is one retaining wall block I use often. It is very similar to the Allan Block that BridgeMan mentioned. If you go to that page they provide the specs and installation instructions so you can see how much work you'll be in for.
 
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Old 10-01-13, 11:16 AM
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There are 4 major retaining wall products (Allan Block, Anchor Wall, Keystone and VersaLok) that are very similar and are used globally with the good product support, specifications and installation instructions. Keystone is the only one (I think) that relies on the pins to be used on some styles. There are numerous "knock-off" units made in most areas that have some compromises.

They all rely on a well compacted base (never concrete) that can be leveled in steps and they all can be used for stepped elevation and curves (inside and outside). It is not necessary for the compacted base or first course to be below frost.

On problem with this particular site is the planning and location relative to the back slopes that can increase the loads. Also, no mater what type of wall you build, there will still be the excavation with the amount of roots you will encounter. The segmental walls will be much shallower and easier to install as opposed to a rigid reinforced concrete or reinforced concrete block wall.

I saw one curving segmental wall in Spain that was about 4 miles long on a mountainous road that varied between 2' and 25' high.

It is best to set out on your site with some colored string or ribbons and try to come up with a location or layout that fits your site and decide what trees you want to keep.

Dick
 
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Old 10-06-13, 07:39 PM
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Thanks all for input. I'll be talking to a local landscaping/excavating company sometime in the next few months and hopefully at least can get some plans drawn up.
 
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