V-DITCH forming

[Zogman]

I'm close to having the rough grading completed for my garage pad. I have a couple severe slopes that my grader dug out a V-Ditch with his backhoe. So it's in the right shape but now I have to pour the concrete. I can figure out the wire mesh and the cobble to secure the wire but I do not know how to form the V for the top shape of the concrete. Searched the web and can't find squat. Any ideas? Thanks

 

[signcrafter]

I'm not a concrete guy but this is how I would do it with my limited knowledge. I would frame up the two outer forms at the height you want. Then cut a V board to use as a screed riding on top of the two outer forms.

 

[cyamaha2007]

Pics would help. Are there multiple ditches that need to match or just 1. If its 1 i would just Hollywood it. Drive pins on each edge of your ditch ( ideally 4 pins marking each bank. Then after the crete is in place run string lines pin to pin to show you where the ditch should be. Also figure your rate of fall during pre pour and cut the edge forms to match the ditches profile. Maybe try searching concrete swale.

 

[Always_Thinkin]

I agree with signcrafter.

 

[Zogman]

Thank you very much for your responses. Here is a picture of one of my ditches. It curves near the bottom. I know I can make a form for the 2 outside wings of the ditch but I'm not sure how I can keep the concrete from pooling to the bottom. I imagine that I will have to mix the concrete pretty dry but I'm still lost on how to keep the ditch with a good shape throughout the V. Sorry if I am not up to speed as the rest of you are but I've never free formed concrete. Thanks again.

 

[gpflepsen]

That will be a ***** to place with concrete. The wall angle will really tend to allow the concrete to sluff down. Finishing will be tough, as it's all well below your working level.

Just a consideration; bury some 4" drain tile and concentrate on a good collection pit/entry point. You have the trench, just lay the pipe and back-fill.

 

[Zogman]

My approved engineered plans with the county have a V-Ditch called out. Not sure I can change that at this point.

 

[gpflepsen]

What are the dimensions? Width at top, depth in middle, angle of wall slope, etc. Total length? Are you doing this alone?

It looks like it's rather small, ~18" wide, 12" deep...

Are you going to mix as you go or have redi-mix delivered?

 

[brownbagg]

they pour concrete like that every day, you pour dry. start at bottom, and shovel up the slope. have a 2x4 at top for edge form and dry pins or rebar in bottom v for flow line, also install weap drain in side to keep ground water from floating the concrete

 

[Zogman]

The open dirt V ditch right now is 36" wide and about 18" deep. I will be doing this myself with some help. I was told to have cobble blocks to tie and hold the mesh. What are dry pins??? So if I have a rebar at the bottom for a flow line, do I just cover the rebar with like a 1/2" of concrete??? Thanks

 

[cyamaha2007]

For the wire mesh id skip the cobble. Hammer rebar pins into the soil vertical. Tie the mesh to the rebar pins. You will have to work from the bottom up. The concrete will have to be pretty dry so your time to work with it will be low.

 

[Zogman]

Thanks for the info. In what pattern should I put the rebar to help me to keep the 3" depth? Sides and bottom? When I pour the concrete, do I make sure that I just cover the rebar studs? Sorry if these are lame questions. Thanks again.

 

[xyster101]

I am not an expert but I have poured a few trucks of concrete. Sounds like you are a bit over your head on this. I am only concerned because once the concrete truck shows up, you have to go, no time for changing plans. Everything needs to be ready, planned and set up once the truck shows. As you pour the mixture, the concrete at the end of the truck gets mixed more and is harder to work and will start to set up faster. You will also be pouring a really dry mix which takes a lot of effort to move around. Also a truck will give you a certain amount of time to off load, usually 6-8 minutes per yard, then they start charging a per minute rate which will add up quickly.
I am going to assume that "dry pins" are the form pins. I would lay out some furring strips or 2by material to form a nice top edge using form pins.

It doesn't matter how the rebar rods go into the V sides, just as long as the mesh ends up at least 1" off the dirt as you pour. I would drive the rebar even with the level of the concrete. So if you want 3" of concrete, leave them 3" poking out. Then as you screed over them, once the concrete is level, you hit it about 1" lower with a hammer and then smooth that area out.

I think I understand what someone said about weep holes, maybe installing 1" pvc pipe through the concrete to allow water to leak into the V ditch from underneath it, but I am not an engineer and don't know if this will allow water to leak out of the form and go under the concrete. Water is persistent stuff and never gives up destroying what we build. So if something is created a little off, water will keep trying to get in.


A french drain covered in gravel or 4" drain pipe seems like a simpler way, but this was approved for a V ditch so you must have a lot of water going into it. Might want to call around to some concrete guys, might be worth the $400-600 extra to have professionals do that.