Concrete form question for segmented wall for curved veneer work
I’m designing a patio that is between 6′ to 8′ above grade (grade rises up around the sides). I was going to detail the wall that backs up the veneer stone to be fabricated with concrete block thinking that would be the easiest way to create the curve, but the engineer said due to the height of the wall, I would be better off designing it with segmented 2′ standard 8′ tall concrete panels and let the stone veneer work be installed on a curve against it.
Is this how others would do it? How would the 2′ panels be fastened together? The panels on the interior, 10″ away from the exterior panels would be on a tighter radius and less than 2′ wide.
Any suggestions on how to form this retaining wall?
The inside of the circle would filled with compacted gravel and topped with a slab for stone pavers.
-Travis
Replies
Any retaining wall that high needs to be engineered -- the forces it must withstand are substantial and you can't just throw together CMUs or concrete panels without some well-designed mechanism to hold them together.
As I mentioned in my first post, an engineer is involved and the retaining wall could be engineered out of concrete block or a poured wall. Engineer feels a poured wall would be easier. I'm just wondering if there's anyone on this board who has had experience with large curved walls and have heard the best way to form them?
I'm interested in HOW it's executed. The engineer doesn't care so much about that as long as they have the right rebar and sizes.
Well, a curved wall can always be poured curved, vs in flat segments. It's "simply" a matter of finding the right folks to set up the forms (and paying them).
Travis,
the curved form and poured is the way I'd go unless the engineer thinks it's an idea he couldn't back up with the figures. Rebar details are important as well as footings out front of the wall with turned up re-bar that enters the forms and poured wall. This keeps the wall firmly attached to the footing which extends out from the retaining wall. Think of an "L" shape.
The only way I've seen it formed is with interlocking narrow steel forms.
Curved forms.
I have not poured any 8' high curved forms, but have done 4' high 10" thick curved forms and walls. It is doable , but most people doing form and pour work these days use standardized panel, thus the2' sections your engineer mentioned.
Call some commecial concrete companies. You are looking for custm work, not someone trying to use standard forms and make it close to custom. Depending on the radius of the wall plywood forms can be built up of layers that can be bent to match the curve.
As Calvin pointed out, the footing and steel are important. Comercial/industrial guys are use to this type of work.
Expect to pay more $$ for thier work.
I'm just a dumb carpenter but if someone asked me to figger this out, I'd be thinking of building the concrete form like two facing curved walls; i.e. jigsaw a couple layers of 3/4" plywood to make the top&bottom plates and some 2x6 studs every 12" or so depending on the radius covered by some corrugated sheet steel. Pre poured footing and Standard tied rebar meshwork inside the wall, of course.
DC
Wasn't born a dumb carpenter, but
ended up one.
What's going to hold that standard tied rebar wall to that pre poured footing?
Calvin
I would think you could stub out anchor rods or drill in dowel rods. A keyway is good to have also.
Kinda standard issue stuff around here.
DC
Stubbing out for a retaining wall is a bit more .......
than standard stuff. The whole system is important. A real thick well barred wall would fall over with just a little bit of ground on one side of it.
The footing and it's placement and connection to the wall above are the important part.
Not just standard stuff.
calvin
Not sure what you're talking about.
Standard retaining wall stub out is 24" vertical #5 rebar anchors triple tied or welded to 2x2 #4 or #5 reinforcing grid but I could see doing similar with a #6 x36" or even #8x36" dowel rod that is drilled and epoxied into the footing. Wide offset footing with keyway and don't forget the drainage holes.
Like I said... Standard issue.
What do you do different?
DC
Initially your standard issue lacked any detail......
and this place is read by alot of different levels of achievement. So, you know you've got to spell it out a little different. There's no joist system holding this apart. And another important point is the footing placement. Wide offset just begins to explain it.
Here, and I'm just south of you, the concrete pourers I've followed would have used bar embedded in the footing and bent up continuous. Lateral bar as determined appropriate. The keyway is usually not done, unipour, waterproofing for sure-drainage out and around if possible. Stone backfill with silt mat behind. Buttressed if necessary according to length of wall.
Details thought out according to site conditions.
You can do the same with block.
edit: I'm still waiting to hear about this wall from the OP. 6-8' above grade with the walls going up around the patio is the way I think I read it. So, is the patio on top of the retaining wall and it holds that, or is the wall up around the patio?
You have any ideas on that?
Calvin
Again, I'm just a carpenter - no fancy engineering degree - but I don't see an 8 foot tall curved retaining wall as much of a challenge. I would assume that the curve (either direction) would assist the structural rigidity. I couldn't imagine needing buttressing as the OP seemed to indicate that the patio was at the top of the wall so stable/level/drained surface. Buttressing would just add complexity. If extra caution is desired, I could see adding some simple steel deadmen durning the backfill lifts but probably not necessary in this case. I'd probably just let the engineer design the footing but if I had to guess I would assume somewhere in the neighborhood of a 36"x12" footing with the wall resting half a wall thickness inboard of the outer edge - leaving a 21" leg on the inside for a 10" thick wall.
Not sure what you mean by "joists" but if you mean form ties, I would just use common 1/4" threaded rod spaced incrementally through the 2x6 strong backs. Then after the pour, I would just clip them off with bolt cutters. Keyway isn't entirely necessary but it's a nice and simple to achieve detail that would make me feel better.
I advocate a two part pour because it's easier - less that can go wrong. I would think this especially true for a curved wall. But I'm not a poured wall expert either. Find a poured wall guy and he could certainly pour the wall monolithic... but would his curve be right? I think you'd just get whatever his form panels gave you which would likely be 2 foot facets.
The more I think about it, I imagine the look of the wall using corrugated metal would look really cool... maybe cool enough to skip the veneer (I might have just saved the OP a couple grand).
"... I'm just south of you.."
How did you know where I'm located? Hard to know who's who, who knows what, and where anyone's from now that the user profiles are erased.
DC.....as in Dreamcatcher Design&Build
Remodeling Contractor just outside the Motor City. :-)
motor city/glass city. Miles apart. You've given your location
in your posts b/4.
I used joists meaning a basement wall held from collapse by the floor system. 2' steel forms are not the only width available.
Site built forms are fine.
I still do not know what level the patio is on. I think I do remember him saying the details are drawn from the engineer, he was looking for information on ease or difficulty of install.
I still do not know what level the patio is on.
"I'm designing a patio that is between 6' to 8' above grade"
I see that, and I see this...........
I'm designing a patio that is between 6' to 8' above grade (grade rises up around the sides)
up around what?
I took that to mean the retaining wall is 8 ft. high at the center of the curve but decreases to 6 ft. high as grade rises up the hill and around the curve of the wall. The patio would be at the top. I imagine there is some sort of drop-off or hill he wants to build this patio on and he wants to 'bump out' to create a patio at the top of that hill.
DC
Thank you
I have a feeling it'll be built b/4 he comes back to respond. Meanwhile we can argue the shit outta it.
I just love this "new" BT.
Always Helpful, Sometimes Clear.
Curved wall forming
As you already have an engineer involved in the project I am going to forgo all the discussion of footing sizes and rebar detailing. Your engineer will take care of all of that as well as drainage and backfill concerns. There are several ways a curved wall can be formed. The simplest way is as described by the not so dumb carpenter engaged in this discussion with the exception of the metal panels he described. I would use plywood or masonite depending on the radius of the curve. 3/8th inch ply in two layers can be used for larger radii, or if the radius is tighter two or three layers of 1/4 inch masonite, tighter yet and you can go to maybe four layers of 1/8th inch masonite. 1/4 inch all thread rod makes a fine tie but you could also use regular snap ties with this system.
I'd like to get back to the 2-foot panels mentioned in the original post. If these panels are to be used you will have to place shims between the panels on the outside radius. I have formed many walls like this using Symons Steel-Ply forming system. You have to calculate the difference in the length of the forms and place shims as required between the panels on the outside radius. If the radius is fairly large you may only have to shim every third or fourth panel. Take a look at the Symons web-site and you can see a few pictures of the forms used on a curve. The Steel-ply brochure that is downloadable has a brief explanation of using the forms for a curve. I have successfully used these forms in curved walls as tall as twenty feet. Good luck.
Concrete Forms
Depending on the radius this is easily done with standard forms. I'm currently doing a foundation with 5 radiuses at 10' tall. The 6'6 radiuses we're doing in symons steel-ply with 14" outside panels and 12" inside panels, the 20' 6 radius we're doing with advance forms (1-1/8" forms) with 24" outside panels and every once in a while using something like a 22" panel. Easy stuff, do'em all the time in st louis.