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Plywood Concrete Forms

22557 Views 33 Replies 18 Participants Last post by  fjn
Does anyone have any idea how tall of a wall you can pour with 3/4 inch plywood forms just using cams and ties? If I make the ties close enough together does it matter? Im looking at a job that has a 16 ft tall by 90 ft wall and a 20 ft tall by 50 ft wall. Worried about possibly blowing the forms and 1 inch formboard is hard to get ahold of. Thanks!
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Looks like an Australian product. I was hoping to not buy forms, due to cost, and the fact that most of the concrete we do is cut up infrastructure stuff, lots of angles and wing walls.
I have built a lot of walls out of 3/4 that were 16' feet tall. Ties were drilled out 8" from the edge and then 16 oc in the field. If poured at a safe rate the forms will hold just fine. Walls that tall would get 2 kickers per strongback.
You can do it with 3/4" form ply. It will be pretty expensive though.
A wall that size.... I would use a double waler system (maybe even up the size of the lumber to 2x6) and place my tie holes at 10 to 12" o. c. at the bottom for about 4 or 5 rows.
How thick is the wall going to be?
I would not consider pouring a wall that tall with plywood. I would find a supplier who can rent you some symon forms. Only way to go, imho.
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I second renting some Symons or the like.
Whats the application? That would be a very time consuming snap tie and waler build...
If you have access to a crane gang forms might be a good option.
Tie spacing and whaler spacing are all dependent on the height of the pour and thr rate at which you fill the form.

ACI 347 is the standard publication that will give all of that information. I would suspect that the spacing would be fairly close unless your fill rate is very slow.

I keep a copy of the standard in my office .
I'd contact EFCO or Symons.
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This is a wall on a dam. Its 12 inches thick. I expect the fill rate to be fairly slow. Like I said I like ply because of the cut up nature of our jobs I can use the ply easier. And I came up a carpenter so its easier to do for me. It will run 3800 to rent symons for the first job, but I am bidding 4 seperate projects at the same time though so I figured I could buy the ply for about 7 and it would last me for a few years. But I don't want any blowouts thats for sure.
Whats the application? That would be a very time consuming snap tie and waler build...
If you have access to a crane gang forms might be a good option.
I've only used 3/4 ply on 24" and less forms.

All other ply forms have been 1-1/8" ply.

Check with the pro form setters, they do this daily and can probably have half the forms set before you are unloaded ....

Definitely worth a call ....
To do 3/4 forms you are also going to be buying a lot of 2x4's also.

It's not like you couldn't build the gang forms with e-beams and super studs.

There is also Doka Framax system. they could be build in place then pulled out and used again in gang form. Have done that before. :laughing:

Leave the 1 1/8" panels where they belong on a residential job.
In warm enough weather and a slow enough pour rate you could probably do it with a 12' x 12" hole pattern according to ACI. that is a lot of ties. Walls like that you should have a professional design. Are you looking to use plywood because that is the system you own?

if it only the two walls, It hardly calls for a large gang system unless you already have one. they are the best in repetitive situations.
Like I said I have done 3/4" form walls that were around 30'-32' tall. We built the walls 16' for the first pour. Then jumped for the top pour. All with the standard 16" layout. To do stuff like that you need good carpenters and pour team.

I prefer a good jump deck system but you know. You build with what you got and you do it good. :thumbsup:
This is all 3/4 plyform. You can really go how high you want as long as you brace enough and your vibrator is long enough I suppose.


I agree you can go fairly high with ply, I have done 8-9' house wall no problem with walers though. Look at how Hungry Horse dam was done. Nothing but 1x lumber with walers and that is a pretty big dam. Or for that matter concrete elevators done with 1x slip forms. all in the design and bracing.
MEVA light panels the fastest way to go. They strip the best and can be hand or crane set. I would gang a wall that size and crane set it. Efco or doka are good options also. At minimum symons panels but plywood is a no no. It can be done but too $
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