[TheForge] Concrete forms OT, but important... for me anyhow.

[Peter Fels & Phoebe Palmer]

Too bad...i have a bucket of snap tie clips rusting here...
Obviously, the concrete pressure is a function of height
and the blow out force at the bottom of an 8' wall is surprisingly large.


On Aug 12, 2014, at 7:04 AM, Dan Brewer wrote:

The plywood will work if and only if you provide a framework of 2X4s on the
outside with clips to keep the sides form bowing.  Along with a lot of
bracing.  5 feet of rise is a lot of weight.  Your local masonary store
will have the form clips you will need to use.  Used motor oil is a viable
release agent.  Brace more than you think is necassary.  Do more research
on line for how much steel you need to put in the wall. Post some pictures
for us to see,

Dan in Auburn


On Sun, Aug 10, 2014 at 5:20 PM, Andrew Vida <osan at netlabs.net> wrote:

> The excavation under the house is now more or less complete.  I removed
> about 400 yards of clay from under and just outside the house.
> 
> The house is now standing on 18 high strength stilts that I fabricated
> from drill string.  It is a weird sight, what with all that daylight coming
> in from under the old footings.
> 
> My question is this: would 5/8 plywood suffice for concrete forms? The
> tallest section to be poured is about 8 feet, about 4 feet wide.  The rest
> is averaging about 5 feet.  I will be using 12" snap ties, on 24" centers
> with two layers of 2x4 criss crossing per the usual practice.
> 
> I was going to use 3/4 OSB, but am now having some second thoughts because
> of the tongue and grooved edges.  3/4 ply is painfully expensive, 5/8 being
> notably less costly.  My concern here is whether the 5/8 has the strength.
> 
> The damned lumber for the forms is almost as $$ as the concrete itself and
> the wife is having a heart attack at the costs.  I'm trying to be as
> efficient with the money as possible, but do not want to make the mistake
> of using insufficient materials.  A blow-out would be very bad, as you
> might surmise.
> 
> One other question: because I am forming to the irregular bottom of an
> existing footing I was going to rough-trace the profile onto wood, cut with
> a scroll saw, and fit it that way.  Has anyone here done anything like this
> before and if so, how did you build to the footing?  Since I have couple
> hundred tons of clay handy, I was thinking I might use it as a sealant to
> close up the little crannies at the top.
> 
> Thanks much,
> 
>    -Andy
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