Pictures should explain this. I’m seeking to build a two tier retaining wall of block then covering with stone as shown below. Footers will be 8″ in depth for the lower wall by 16 inches width. Considering overall weight, top wall will be reduced to 6 inches depth. Also rebar will be placed in footers. Is there anything else I should consider?
Perforated drainage pipe and stone will be installed against wall before fill.
Location- North Georgia
More here–
http://cabininthemountains.blogspot.com/2008/09/retaining-wall-with-stone-in-progress.html
Replies
hwg.... i looked at your pics... looks like a 4' wall ????
seems like overkill... i'd put in a footing of crusher tailings ( 4" stone )...
run my drainage ... then build a dry wall of field stone vertical battered wall front
sloped to the rear.... filter fabric, gravel backfill...
loam & seed
Yes overkill, but I need some experience with footers and concrete block before the addition next spring/summer. Trying to keep the stone look same as foundation of cabin in pic.
I don't follow these terms
vertical battered wall front
sloped to the rear.... filter fabric
thanks
a vertical wall would be just that... battered wall means it would slope back from vertical.. on a 4' wall... i might batter the front about 4"
the rear would slope at about 45 deg. to resist the overturn moment of wet earth
filter fabric draped over the rear stone will prevent the earth from infiltrating the stone nd defeating some of the drainage capabilities of the stone
your retaining wall and your new addition don't neccessarrily have to be the same type construction
how high is your wall that you think it requires 2-tier ?Mike Hussein Smith Rhode Island : Design / Build / Repair / Restore
filter fabric draped over the rear stone will prevent the earth from infiltrating the stone nd defeating some of the drainage capabilities of the stone
Coincidentally enough, I just got off the phone a few hours ago with a client who subbed out a retaining wall that has some issues. She spoke to a geotechnical engineer who told her that improper placement of the geotech fabric (let alone not using it at all) would result in a 50% reduction in strength.
Lower wall footing isn't wide enough to prevent overturning.
You have an initial load of the first 4" vertical with the second walls load added to it.
I wouldn't do the footing any less than 3' wide for the first walls footing for the total 7" height and then I would set the wall off center either to the front or back of the footing.
Create a "Heel " and "Toe" to prevent overturning, yes bar in footing and wall and make "L" bars that come out of the footing and run to the top of the wall.
Everyone seems to like the word, "overkill". Couldn't get more than a laugh from the planner with that design around here (Colorado). Looks like the drive comes in from up hill and cars would be parked here. You checked this with structural engineer? Tyr
I missed the parking area in the picture. Add a surcharge load from that and that 16" footing is ridiculously small.
They can't get your Goat if you don't tell them where it is hidden.
Structural engineer? It's just some simple walls out in the sticks. All the DIY sites says I'm in the right area...LOL. Yea, I used to field DIY questions too in a different business and I always thought, pay me now or pay me later.
"how high is your wall that you think it requires 2-tier ?"
The heights look to be 32 inches on the lower wall and 24 on the upper wall...it was an idea and nothing else. Three foot wide footer? Seriously? Maybe I'm looking at the wrong sized block? I was thinking standard 8-8-16. The heel thing makes sense.
Incidentally the soil in the parking area is hard Ga clay. Damned hard, I've dug though it. I wouldn't suspect much movement or am I wrong? Yes, the strenghth of the upper wall is a concern because of cars going over the hill. Beat what's going on now. I've almost gone over it.
Btw, parking area will not be used often with a roundabout drive planned away from the area in photo.
Loads on that wall are figured from the base of the footing at the dirt side. Draw a 45 deg angle up and towards your parking area from that point. Everything that falls into the triangle created by the walls, the top surface of the retained soils and that 45 deg line falls into the area of load.
Add to that any vehicle weights (surcharge load) and that becomes the total load on the wall. Breaking the wall isn't as great a concern as overturning it is. I am not an engineer , just a dumb builder.
The project I am currently working on has an Engineered 7' high retaining wall in Oregon clay/weathered basalt.
Footing is 4' W., 12" D with #5 bar and #4 bar in footing plus "L" hooks at 16" o.c. of #5 bar plus the hor. wall reinforcing of #5 bar.
If final plans show a vehicle surcharge the footing gets even wider (to 5'6"). Just giving you my best shot based on my personal experience around retaining walls. the example I just gave you is within the common range I have built over the last 35 years in this business when an engineer does the specs.Edit: I thought you said the wall was 6' high total, I may well be mistaken.
"I had originally planned on building a seven foot retaining wall around the parking area (shown below). Wall would begin at the yard level in the foreground and extend two feet above the gravel parking area. My part time resident critic Mom says it would be awful. Instead, "how about two walls?" Guess not. It is what you posted in your blog.
Edited 9/29/2008 12:28 pm by dovetail97128
Ooops, the blog was original rough numbers dated a few weeks ago I believe. I have been into other projects since, so no updating had been done. Here I was almost ready to go with a dry stacked fieldstone wall overriding my other stubborn ideas set in stone.
So dry stacking must be safer/more feasible because of drainage? At least that's the way I am seeing it. Very good reply..thanks..anybody else?
Can we vote?
1- Kill the block mortered stone idea
2- Go with dry stacking
Yea, that definitely seems overkill to put in actual footings and block walls. I live on a block of houses where most of us are 4' - 9' above the sidewalk. Those of us that replaced the 70 year old retaining walls with dry stack block (including ours) look fine. Those that used any sort of block (solid wall, mortared cement block) all look like #### with cracking everywhere.Remember that the wall isn't holding up the entire hill...just the dirt coming from a 45-ish degree angle upwards from the base of the wall. Better drainage will trump brute-force over-construction (fabric, rock backfill, tile). (Though note that all of the above was said by someone that's not actually an engineer of any sort...)