I need to build a short (3 feet high or less) retaining wall on a hill at my house. I want to make the retaining wall a semi circle. The elevation (ground level) changes dramatically over the area where I plan to build the wall, so establishing a level area to start from would be very difficult. I’m thinking about building it like marine contractors build bulkheads. I’d place large timbers or pilings in the ground like fence posts making sure that I had at least as much in the ground as was above it. Then I’d put two (maybe three) horizontal stringers between the posts on the “uphill” side. Then, one at a time I’d add vertical 2 x 8’s, also on the “uphill” side driveing them partially into the ground and attaching them the the horizontal stringers. I could then cut the top of the vertical 2 x 8’s to make the top even and level eventhough the ground level is uneven. I’ve included a sketch that will hopefully clarify my description. Does anyone think this won’t work?
Replies
That sounds like LOTS of work.
Why not the modular concrete wall stones. You can step the footings on them as you go around the hill. Many of them are rated at 4 ft without any extra engineering.
yea, what Bill said.boblVolo Non Voleo 10Joe's cheat sheet
If you do the wall that Bill mentions, plan to spend any extra time you have getting your footings level. The footing will probably only need to be crushed stone, but you'll be happiest if you get the first course to line up perfectly--with the block sides perfectly flush to each other and tops perfectly level (and I mean perfect)--be/c slight imperfections will telegraph through to the upper courses. We did over 1000 sf of this with Mesa block, and are quite happy, especially knowing that we should never have to replace it.
http://www.tensarcorp.com/role/content_mesa_faces.htm
It would be my preference to use the modular concrete wall, but there are so many level changes in the 60 or so feet in question, I'd have do do an awful lot of digging. The ground level rises then drops, rises again and drops again, all in differing degrees of steepness. getting a level foundation, even if stepped would require a lot of digging. Also, just beyond the wall the hill gets pretty steep, so I'm thinking having some posts in the ground might be a good idea.
I've seen something similar to what you want done by driving steel "I" beams (the font needs serifs) vertically into the ground with their flanges in the same plane and their webs perpendicular to the intended wall. Then they just dropped timbers into the channels created by adjacent "I" beams. For a curve, you'd probably want to use short timbers, so old railroad ties might be a natural.
-- J.S.
Chuck, what is the purpose of building this wall? Can you see this from the house, deck, patio or whatever? Do you want a fairly level area in front of the wall for lawn, parking area, patio, or outbuilding? Can a small backhoe get to the site to do the digging?
I'm just not sure of the purpose, so it's hard to make any recommendations, although I agree with the others about the pre-cast block route over what you are thinking. Either way, you need to run drainline in washed stone wrapped in fabric behind the wall to relieve the hydrostatic pressure.
Let us know more about why you are doing this.
Bear
The purpose of the wall is to expand the yard a bit. A rotting retaining wall was built to allow them to build up the area for a pool. I want to go a bit higher. Beyond the wall the hill gets real steep real fast, so bringing in equipment isn't practical, perhaps impossible. Asthetics aren't really in play on this one. From the high side, we won't see the wall at all. From the low side, it's really not possible to get close enough to really see it anyway. The only person that will get a close up look is me while I'm building it.
a bobcat or small tractor with attachments can't get in?boblVolo Non Voleo 9Joe's cheat sheet
It might be possible for them to get in, but it's close enought to the steep part that a miscalculation could result in the loader beingat the bottom of a very long steep hill!
Chuck
Theres nothing wrong with your idea. We often build them up to 8 foot high. Only diff is loose the 2x6 and run your 2x8 horizontal as whalers. Cheaper and looks better. Lay some gravel at the back of the retainer for drainage and backfill.
Nigel,
How deep do you usually go with the posts? Should it always be equal to the height or is there a point of diminishing return. Or.... should the post be deeper than the height?
ALL our retainers are Engineer designed. Rule of thumb is no more out of the ground than whats in. Depends on soil type, surcharge etc.
You might check with your local building department. In Los Angeles, they publish a generic retaining wall design that they'll accept for any wall up to 3 or 4 feet.
-- J.S.