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-   -   Monolithic forming... (http://www.diychatroom.com/f19/monolithic-forming-3988/)

MLO 09-19-2006 06:29 PM

Monolithic forming...
 
8" deep foooting x 16" wide, foundation wall heigth 16" by 9" wide (matching existing for brick facade).

Foundation is for a "L" shape addition off back of home. 8' out from existing turn 90 deg. then 26' turn 90 deg. then 25' back to existing.

I have the footing framed with 2x8's and have monolithic straps installed on 24in. center. I have my two horizontal runs of rebar suspended from the mono-straps.

Will 3/4" plywood be strong enough to use for form panels with the mono-straps and cleats installed on top on 24in center? I would be ripping 16" widths out of 4x8 sheets as the wall is only 16" high.

This seems to be the cheapest and easiest way to do this as panels would cost near $400 to rent and they would be 24" tall requiring a chalk line at 16" and a more cumbersome finishing process.

Any insight?

joasis 09-19-2006 09:50 PM

Simple answer is yes, 3/4 is what to use, properly braced, and it sounds like you have it down. Good luck.

mdshunk 09-19-2006 10:07 PM

Yeah, the worst thing that will happen is that your forms will bow out a little and you'll use exactly $400 in extra concrete. :jester:

KenTheHandyMan 09-19-2006 10:48 PM

You'll be fine, again, provided you brace everything OK.

You are stating that you will have 2x material running along the top of the forms, right? How will you be making sure they are straight? Your bracing should do that.

If you are going to be using this form as a guide (which you should) take extra precaution that the top of the form is straight and level. When you're finishing the wall, your tools will be resting on the form. The wall won't be any truer than the form. Rip straight. As you rip a piece, sight the remaining material to make sure it is straight. In something like this, I usually only rip two pieces from one side, then flip the sheet over and rip the rest. I do this because the factory edge is generally truer and every time you rip a piece off, you tend to 'bend' it a bit. Ripping from each of the two sides tends to minimize that effect.

MLO 09-19-2006 11:14 PM

Let me ask...what would be easiest way to brace the panels and top with 2x's?

Should I run a 2x band a few inches from the top of the plywood and brace diagonally to the ground?

KenTheHandyMan 09-19-2006 11:35 PM

I would actually screw 2x4's flush with the top of the forms. Offset them lenghwise so that you are staggering the butt joints. This helps hold the forms together and makes the whole thing more ridgid.

Then you'll stretch a TIGHT string just over the top and line the forms up with that string (Vertically). To do that, place a stake in the ground so that a 2x can reach the top of the form on one end, and a stake on the other end. If you miter the end of your brace, you'll be able to screwl it below the top of the form. If that's too hard, you can screw it to the top but when you finish the wall you'll have to bump around it a bit.

Then pull your form straight to the line and screw the brace to the stake. I'd do this every 6 feet. It's kinda hard to describe this with letters and words, so don't feel bad if it's tough to understand. I'm doing my best. :)

Just remember, you want your foundation straight and level. Everything else will depend on how good it is.

MLO 09-19-2006 11:54 PM

Thanks Ken...comprehended!

Should the 2x4 be screwed to the top of the forms on edge, or does flat (3 3/4") to the form seem sufficient for my project?

MLO 09-20-2006 12:36 AM

I found some schematics for reference and will just frame the panels in with 2x4's (on edge) like for normal forms. I was taking this a little "light" thinking the wall is only 16" heigh. I certainly want the end result to be nice.

Thanks again!

KenTheHandyMan 09-20-2006 09:38 AM

Make sure your bottom is sufficiently anchored (something I didn't touch much on in my previous posts). The bottom is where the greatest amount of pressure is and is consequently where a blowout is likely to occur.

MLO 09-20-2006 12:07 PM

I have the mono-straps/cleats placed every 24" on the footing 2x's. Is a screw through every cleat (theres a hole) into the bottom of the panel sufficient?

I was going to box frame the 16" panels with the lower horizontal 2x being about an inch up from panel edge where it fits into the cleat tabs. This gives room for the panels to fit into "cleat tab" so the bottom 2x does not bottom on the tab or need to be relieved.

Now that I think about, I have premade clips for the top of the panels that also have the metal "tabs" to fit over the panels. I like the idea of running the 2x's flush with the top of the panels, maybe I should just use 1x's to tie the panel tops together instead of the clips and not have to deal with the "tabs"?

Sound ok?

KenTheHandyMan 09-20-2006 12:19 PM

I think you're good to go. ;) Can you take a picture when all done before pouring?

MLO 09-20-2006 03:28 PM

Hankering for some comedy eh? The wife is already snapping photo's so once I get things underway I will share some.

Mr. engineer has called for the installation of some PHD2 & 5 holdowns. How do you figure exactly where to locate these so the hardware will pick them up? does not seem like there is any room for error!

The general notes from my munincipality say that all j-bolts need to be placed and tied off before the pour. I typically thought these could be installed after leveling off the forms? atleast that is what I remember 15 years ago. What is the best way to tie them off?

K2eoj 09-20-2006 05:52 PM

I've never seen this type of monolithic pour done but it sounds like it might be common in the Norhtwest. Even though your only 24 inches high I think you are under tied. A screw into the end of 3/4 ply @24 in oc is not going to hold didly in my opinion. I found something on your mono straps and it looks like they are designed for a specific form system. And what keeps your mud from flowing out and over the bottom footing form??? From what I'm hearing I would want the bottom of the footing form strapped/tied together and more strapping or a better fastening system, and whalered on the bottom of the wall.

My rule on concrete forming is what i think will hold x 3 and I've still have had plenty of blowouts. Blowouts :censored: and they are hard to fix and it makes you work 10x harder and it is embarrassing and they look like crap afterwords.

Or maybe I'm not getting a clear picture of how this works???

But if this is your first pour, tie the crap out of it. A well tied wall can stand on it's own with little bracing.

MLO 09-20-2006 07:19 PM

Seems mono-pours with footing/slab are common but not footing/wall. With my jobs smaller size, doing two pours would cost more with delivery minimums. I also need to rent a pump as the job is landlocked in the back of a home. So this method was mentioned by a contractor as the most cost affective. I had no intentions of taking this on until I recieved a couple bids from $4-5K, that got my attention and created some motivation.

It was explained to me that a stiffer slower pour would be used for the initial footing fill and actually little to no concrete should overfill the opening outside the form panels on the footing forms, or very little.

It is my first pour besides sidewalks and such and certainly will do everything I can to avoid the attempt being a waste of both time and $.

I'm all ears and appreciate the insight, TIA.

K2eoj 09-20-2006 08:58 PM

I didn't see th part about the cleat tabs the first read through. Sounds like that would do for the bottom of the wall form with your 2x whaler. I think I would try to strap the bottom of the footing form. I sometimes cut up a lumber banding strap and pop a couple of holes at the end of a say 20" piece. Slide it under the form and nail it into each side of the form. It doesn't have to be tight.

If I was going to rely on stakes on the bottom of that footing form I would have alot of stakes. Your stiffer mud should take the pressure off that form but if things go wrong it is better to have too much holding power.

Sounds like your doing your homework. Like to see the pics when you get some time.

My area has gotten away from spread footings for a couple of reasons but our min frost dept is deeper. I would be doing a pour like yours with a single 40 " wall form.

Good luck.


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