Concrete form release agent - needed?

[marlow]

I'm building a 1 1/2 storey garage (~350 sf living space upstairs).  

I am considering building my own forms for a concrete strip footing and short wall.  I would like to recycle the forms lumber for the building framing.  I have concerns about air quality and toxicity of any residual release agent left on the lumber.  Some questions come to mind:

1. Is it mandatory to use a release agent on the form lumber?
2. If I have to use a release agent, what kind of products will not leave a residue (toxic, VOCs, etc) on the lumber?

[firefox]

Just guessing her, but you might experiment with something like
vegtable oil on some scrap and see if it works.

Also using clear plastic sheeting might work, but you may have a problem getting it off the concrete. Maybe torch it off after the concrete cures. It might even help in the curing process by retaining
the moisture.

These are just guesses here.
Bruce

[Alan Gage]

I used 2x8s to form up a footing this spring on my build hoping that I could pull them off and reuse them afterwards. I worried about them sticking to the concrete and thought about using some sort of release but had the same concerns as you, that it would make a mess of the wood.

In the end all the worry was for naught. A couple days after the pour the boards pretty much fell off on their own. Didn't stick to the wood at all.

Alan

[marlow]

The idea of veg oil sprayed on the forms came to mind, but then I wondered about rancid oil or other organic matter problems.

Alan has confirmed my suspicions that the lumber could probably be easily knocked off, providing the lumber is smooth faced, without a release agent.

[rick91351]

The only time you really need use form oil or release agent is on foundation panels / basement panels or plywood you are going to use them multiple times.  It is pretty much only contractors that need to keep their forms in good order even mess with form oil.  As Alan Gage says if you let them set for several days before you strip your forms they come off a lot cleaner and you can just scrape them down with a floor scraper or a square point shovel.     

That said after you oil them up the only thing they are good for is forms.  If they are oil up properly you wont use them for anything else.  They are oily and smelly.  Form oil has a smell if it own.  I would however rather smell that than rancid vegetable oil.   

Another reason contractors use form oil is because many times they do not have the couple days to let it sit.  Back when I drove ready mix concrete truck.  We would deliver cement for a footing first thing in the morning and would pour foundation that evening.  Or footing in the evening and foundation the following morning.  I hated to see that but I guess it worked; a lot of those houses are still there today.           

 

[JRR]

I would consider stapling a layer of roofing felt, or heavy visqueen, on the inside of the forms.  Makes a great release plane ... if appearance is not a factor.

[Squirl]

My understanding is form oil is just another higher priced petroleum oil product.  A few contractors I know, just use used motor oil.  Concrete naturally shrinks as it cures.  I have seen someone use plastic for a footing.  Check out speedfunk's 900 sq. ft earth berm.  I have never seen it done on a tall wall.  I don't know if it would affect curing.

Alan, what was the condition of the boards when you were done?  Warped, cracked, dried out?  That would be my only concern was the condition of the lumber with something wet soaking on one side for a few days.  Also concrete is normally wetted down if it is hot.

[Alan Gage]

I wetted down the concrete quite a bit during the couple days because it was quite hot and windy during one day. The wood seemed to be no worse for wear. The straight pieces still looked straight and the crooked ones were still crooked. They just look dirty now.

Alan

[marlow]

I've decided not to use release agent.  I will be experimenting with plastic as a partial or full liner and moisture barrier.  The forms will probably stay on for two days.  If I remember, I'll post the update afterwards.  Thanks for the ideas and thoughts.