I have a barn that was built about 100 years ago. The bottom/foundation is built out of concrete and field stone. It is eroding away. It is about 2' from floor to sill. I was thinking about making forms and pouring concrete. Looking to go on the cheap. Could I use 7/16 OSB sheathing or subflooring? It would save a bunch of money over using plywood. I am open to any other suggestions.
Yeah you'll hafta brace the heck out of it, so that might eat up your savings. Plus the OSB will likely leave wood flakes in the concrete when you remove the forms. Remember, wet concrete weighs about 145# per cubic ft, or almost 2 tons for a cubic yard...so you need to brace brace brace!
Looking at Lowes. 7/16 OSB Sheathing $7.25 23/32 OSB sheathing $15.18 1/2" sheathing plywood $30.57. So there is a lot of savings to be ate up with bracing. Don't really care about wood chips, just trying to preserve. Was more worried about it getting mushy from the water in the concrete. Getting older and are entertaining some thought of moving to reduce maintenance on the place.
There is a release agent that you apply to the sheathing material - keeps that darn flaking and de-lamination at bay .
I've done it with three quarter inch marine. do yourself a favor get a drill bit and drill the holes I didn't get the concrete ties that you can attach to the holes to hold it in place. Basically it's called building your own forms. And then brace it.. 2 feet high not problem what's length and any corners. FYI about 40 feet plus and you need a buttress or support wall..
I used to do walls and flat work. Depending on weather you’re just “patching”, or repacking entire sections will determine the pressure placed on the forms. As said above, using wire ties and 2x4’s with cam locks will make it. Ugh easier. So if it were me, I’d do some looking and asking about older contractors that may have some forms laying around you could maybe rent? I know the guy I used to work for hasn’t used his form-ply forms for over 10years and they just sit. 3/4” plywood or OSB could work with the right bracing. Ties, Rods, 2x4’s, and cam locks make it a solid structure that won’t budge when filled with concrete. Sent from my iPhone using Tapatalk
7/16's will be fine, build a 2x4 "wall" 16" on center and "sheathe" it with the OSB, a baby wall. The most important point is the ground contact, head pressure will want to push the bottom of the forms out, 2 foot up will have minimal preussure. A few 2x4 braces, every 4 feet, and you are good to go. Use diesel fuel as a release agent or form release your choice. Build several sections, pour, remove and relocate forms and pour some more.
Good point...wet concrete acts like a liquid, pressure is highest at the bottom of the "tank". Just curios, how thick will this concrete be?
In my experience form thickness is not as important as the bracing. Even 3/4" plywood is still plenty flexible to cause problems. Consider calling rental places, they have them for rent by me. A failed pour will cause much more of a loss that overcautious bracing.
actually went down and laid the tape measure to it. 8" thick x 16" x 14ft long. That is what I am looking at for now. Next pour will be the same except 45' long. I hadn't gave rental a thought. Will have to check them out.
7/16's will be fine, build a 2x4 "wall" 16" on center and "sheathe" it with the OSB, a baby wall. The most important point is the ground contact, head pressure will want to push the bottom of the forms out, drill the bottom plate and stake it in place with rebar or concrete pins, 16"s up will have minimal pressure. 2x4 braces, every 4 feet, and you are good to go I would also run 2 pieces of rebar inside the concrete wall so when it cracks does not separate. there are 2 types types of concrete cracked and gonna crack.
As Eric VW said make sure that you use a release agent, otherwise you'll be pulling your plywood apart when you're taking the forms down. I've never heard of using diesel fuel I am sure that would work fine. When I was working construction they would always use linseed oil it's a little thicker.
Nah...its common here too...I've even seen large contractors use it. Asphalt trucks spray it in their beds before a load too...plus all the tools/equipment get cleaned up with diesel fuel...usually offroad diesel
