Anyone know about Retaining walls?

[fjdemon]

I have a very steep area next to my house that I would like to build a garage. I'd need to build three sides retaining wall to fill it in and put a a level garage on top. I'm estimating that it would need to be 6 feet tall and around 15 feet per side for the two side walls, maybe 20 feet for the long back wall. Any ideas what this might run to be poured? Thanks, get some ideas before I look any farther. Appreciate it!

 

[lunyou]

If you are thinking about building a garage on top of it I strongly recommend you getting someone that can tell you for sure how it should be done.

You are talking about alot of weight on top of that "fill". That weight will create stresses and other problems on your wall, especially at the bottom. There is a really good chance that the bottom could be pushed out or the whole wall could just fall over.

lunyou

 

[trainrech]

A lot depends on what needs to go under the wall as a footing. Don't skimp on a design since you are putting a structure on it. I'd suspect $2 - 3K. The concern I would have is that the structure is naturally going to want to move down the hill so shoring it will be important.

 

[goschbrandon]

You should get an engineer to hash out the design for ya- this is likely a requirement to build it anyhow. You'll have to be concerned about overturning, sliding, earth pressures, the loading from the garage, moment on the wall, etc. Not a complex engineering problem, but not something to skimp on either.

 

[roscoFJ73]

You might want to look at various systems. The basic types are concrete post and panel,mass stone/brick/block or reinforced concrete..
Good soil compaction is vital

 

[fsusteve]

I'd maybe pm white shark, walls with that much load will need some engineering. I did two walls, the biggest was three feet high by 30 feet or so and about $4k in fill.

 

[Cookiemonster]

Easy actually.

First step is to have an engineer design it out. What they will do is a minimum 8" thick wall with at least a 4' footing with 12' piers from grade & steel beam with metal and conrete on slab.

The engineering report will start at a minimum of 2-3k.

If you plan on doing it yourself you will need to find a vendor for either steel form ups or snap tie brackets. If you start a search for snapties, Don De Cristo wedges/brackets, (ttp://www.westsidematerials.com/pdf_files/catalog_concrete/catalog_page_25.pdf)
Concrete forms Gates Concrete Forms - Adjustable Form Brace
Molded Fiber Glass Construction Products

The cheapest way to do it would be to use plywood and snap ties unless you have a leed on steel forms. The sanp ties will require renting the brackets.

I assure you even doing it on your own just in materials including the plywood, lumber, re-bar, concrete and misc items will cost you 8-10k. Don't forget rentals fees on brackets & heavy equipment (will need an excavator for slope work). Just to give you an initial idea.

If I were you I would call at least two repritable concrete contractors that can show you similar work examples and get quotes. Have them break the costs into materials-vs-labor. Deduct 15% from the materials cost and that is what the materials will run you. Contractors will typically add on 15-20% to cover running around for materials, chasing down permits, engineering changes & office time.

Good luck & keep us in the loop.

 

[fjdemon]

Thanks for the input, I guess I'll be contacting someone locally with some expertise to give me ideas. I know it's over my head hahaha. I guess 10-15k isn't a bad price to have it done right, if less, great! thanks

 

[EricG]

In my area you need an engineer to sign off on the plans for anything over 3'

 

[GLTHFJ60]

Do you guys have a preference between poured concrete and a geogrid dry masonry retaining wall? I've done a bunch of dry masonry retaining walls ( block ) and they can hold a ton of weight. When they start to give, after 20 years or so, all you have to do is re-stack the blocks with new shear pins as opposed to excavating all the old concrete.

 

[Pin_Head]

I learned more than I wanted to know about retaining walls after being on a 10 day jury trial in a civil case about an allegedly failed retaining wall.

1. Everything on a slope moves down hill; it is just a question of how fast.
2. Depending on your area, you may also need a geologist report before the engineer can decide what specs are needed.

 

[HR-OLIFANT]

Hire an engineer to come up with a design. Have them spec. a design for both a reinforced concrete wall and a segmental retaining wall. Make sure they know the loads you intend to have above it(surcharge). Once you have the specs and design, contact some NCMA certified contractors for bids. Walls do fail, usually due to improper design and/or improper installation. But they will outlast you if done right. Check with your local stone/ block yard for contractor recommendations, and you might need permits and inspections as well.

For reference, in the Va Beach/ Norfolk area, I am getting $25 to $30 bucks per square face foot of segmental wall installed.

 

[bkfj40]

I do this kind of work fairly frequently and am licensed in PA, VA, WV, DC, and MD, but not in GA unfortunately (atleast for you). You can look at the project in two ways. Do you want a room below the garage or not? If you do, you're looking at a suspended concrete slab and it will provide you with additional square footage. If you don't, you're going to have to fill that void. The ideal situation is to put all of your footings down below the original grade and fill the interior of the garage with 3/4" stone with no fines (#57). A 5" or 6" slab with rebar and grade beams works pretty good and will eliminate the settlement issues encountered when you fill with other material. Someone mentioned the segmental retaining walls. A good option, but you're going to see a little bit of settlement unless you are using the proper compaction. If you do use the proper compaction, I don't think it is going to be much cheaper, if at all.

I would encourage you to call around to local engineers and get an estimate on cost and a rough idea on how they would design it. As someone else mentioned, most localities require anything with more than 3' of fill to be "engineered"

HTH,
bk

 

[inthewall]

Instead of three walls go with four. Footings below frost level. Just like a house foundation. fill and compact up to top of stemwall. The walls will be tied together and it shouldnt slip. It has to be engineered so you might as well have them design it.

 

[Arya Ebrahimi]

Brian, I was thinking a segmental wall would be easier/cheaper from a DIY perspective. In terms of skill set/tools/overhead(forms) etc, I'd think the segmental would be far easier for someone to do themselves as opposed to learning how to do concrete.

Having coordinated the construction of several segmental walls, I think they're relatively foolproof compared to concrete (assuming the person building the wall can read and implement what he sees on the drawings ;p )

What do you think?

 

[GLTHFJ60]

Brian, I was thinking a segmental wall would be easier/cheaper from a DIY perspective. In terms of skill set/tools/overhead(forms) etc, I'd think the segmental would be far easier for someone to do themselves as opposed to learning how to do concrete.

Having coordinated the construction of several segmental walls, I think they're relatively foolproof compared to concrete (assuming the person building the wall can read and implement what he sees on the drawings ;p )

What do you think?

I agree with you especially considering that you don't have to deal with a cement truck. However, building a block wall isn't as easy as it might seem either. You have to know how to stack them so you don't line up the seams, as well as how to correctly stack and glue the corners. Then you have to measure your elevations, which can be tricky. It might be cheaper to do a block wall DIY than to do a cement wall, but it's more complicated in my opinion. Then again I've never poured a cement wall.

It seems that there are more steps to building a block wall than to pour a cement wall.

 

[bkfj40]

If you're looking for lowbuck and can do it yourself...I'd agree that the segmental retaining wall is going to be the cheapest option. However...what tools do you need to rent to do the wall properly? Compactor, skid steer or tractor, and you still need proper imported fill or stone. If it is going to be hired out - concrete wall might be a better choice.

just don't let someone talk you in to doing a CMU (block) retaining wall - unless they are going to fill the cells with rebar.

I think that Arya was going to donate any extra labor you need to help as long as you provide him with beer...

bk

 

[Arya Ebrahimi]

I think that Arya was going to donate any extra labor you need to help as long as you provide him with beer...

bk

Maybe it's cause I'm a field guy and not an engineer, but I just don't like concrete retaining walls compared to segmentals. Segmentals just feel stronger to me watching them being biult.

Then again maybe I've just been on too many Army Corps jobs and they've got me paranoid about all the proper ways of working with concrete; but the thought of Jose the concrete guy being able to do a proper retaining wall while being supervised only by the homeowner makes me shudder.

Also, just to play devil's advocate, wouldn't you need to rent those aforementioned tools if you were gonna be doing a concrete wall to backfill the wall anyway?

 

[Carpe Discus]

I'm currently finishing up a segmental wall project with about 200 feet of 3' wall, all done by myself and my father (retired). If we can do it, you can too. We decided against poured so we could do it in sections. Otherwise, we'd have to pour something like 80 feet of footing at once, which seemed like a bother in a backyard. We'd have to pump it in, neither one of us has significant concrete experience, etc. It was much easier to do than concrete would have, I think.

All told we probably moved about 25 pallets of 100 lb blocks, and about 40 tons of 3/4 inch gravel from the front to the back.

They can be used for loads with surcharge (like a building on top), but you definitely should see an engineer. I used the standard Keystone units. I wanted to use another manufacturer for appearance (Allan, I think), but was convinced not to by someone with experience. The other manufacturer's blocks aligned not by pins but simply by shape of the casting that can get misaligned--the Keystone units were rock solid and the pins work well.

All this said, you might want to consider just building up from footings in the grade as it is now, and you could have a garage with a basement!