Material for concrete forms?
Mark
a planting area. The edging will be 4" thick, and include bends
with an 8" radius.
Can anyone suggest what materials I ought to use to build
these forms? I'm having difficulty forming the bends using
kerfed plywood. Establishing the spacing between the
inner and outer boards is also problematic (I can't find
any 4" snap ties.)
Thanks
-Mark
Tony Mugno
create snap ties out of scrap wood. Cut grooves in the scraps 4" apart the
thickness of the MDF. Use the plywood for the wood scraps since its wasted
anyhow
"Mark" <nos...@thanksanyway.org> wrote in message
news:q6qdnbZMy-K...@speakeasy.net...
Lyle B. Harwood
<nos...@thanksanyway.org> wrote:
€ Can anyone suggest what materials I ought to use to build
€ these forms? I'm having difficulty forming the bends using
€ kerfed plywood. Establishing the spacing between the
€ inner and outer boards is also problematic (I can't find
€ any 4" snap ties.)
Build the forms from strips of 1Ž4 masonite, which will bend to the
radius easily.
Hold them in place by nailing them to stakes on the outside of the form.
Use as many stakes as necessary to form the radius.
Maintain the distance by measuring, and adding stakes as necessary.
It's not hard, it just take patience.
Best of luck, and let us know how it comes out!
--
Lyle B. Harwood, President
Phoenix Homes, Inc.
(206) 523-9500 www.phoenixhomesinc.com
Mark
"Tony Mugno" <amu...@optonline.net> wrote:
> You should be using MDF
>
> create snap ties out of scrap wood. Cut grooves in the scraps 4" apart
> the
> thickness of the MDF. Use the plywood for the wood scraps since its
> wasted
> anyhow
MDF isn't very flexible, is it? Am I misunderstanding how you are suggesting
this material be used?
The scraps with the grooves cut in them would be placed at intervals across
the gap, to keep the forms the correct distance apart?
Thanks
-Mark
Rudy
> a planting area. The edging will be 4" thick, and include bends
> with an 8" radius.
8 INCH radius ?
Mark
Yes. The inside curve will be an eight-inch radius. The outside
will be twelve inches.
Mark & Shauna
holes. Cut it to the thickness of the slab and stake the hell out of it.
Mark
CWatters
> a planting area. The edging will be 4" thick, and include bends
> with an 8" radius.
Perhaps look at extruded concrete?
Paul Prunkel
"CWatters" <colin....@pandoraBOX.be> wrote in message
news:YRYYc.231666$Ml7.11...@phobos.telenet-ops.be...
Eunoia Eigensinn
You could use a long bread bag for a form if there were such a think.
A 4" wide pour isn't going to require much to retain it in place.
If the concrete is mixed in proper proportions, it should be stiff enough to
stand up on its own almost with the need for forms. You could use something as
seemingly flimsy as thick cardboard or several thinner layers of cardboard,
wrapped in polyethylene sheet (or even the above-mentioned bread bags)to
prevent the cardboard from getting soggy. Form ties can be made from thin
wire or twine, with ends wrapped around small sticks or even nails. The
concrete doesn't care what you use for forms or form ties. Pile gravel, stone
or bricks etc against the outside of the forms if necessary to reinforce the
forms bewteen stakes and ties.
It's not rocket science. It's more like making really-hard mud pies.
All that matters is that the form holds the shape of the wet glop in the
desired shape for a few hours.
There are some architects who like to use burlap sacks to form free-form
columns.
Given that it is outdoor concrete and if it may be subject to freeze/thaw then
it wouldn't hurt to add a bit of soap to the mix as an air-entraining agent
which also does double duty in that it enhances the mix's workability by
helping to retain the water in the mix better, making it a more plastic mix.
Tony Mugno
And yes you are correct about the scraps with grooves used as spacing.
"Mark" <nos...@thanksanyway.org> wrote in message
news:MoidneHGzoD...@speakeasy.net...
Mark & Shauna
> A 4" wide pour isn't going to require much to retain it in place.
In our experience it usually isnt the concrete itself thats a problem.
Its the placement and then subsequent finishing that will get you if you
build flimsy Rube Goldberg forms. You may get the concrete in there but
then when you start to shove it around (especially if you are mixing as
stiff as you suggest) and finish it your forms start to move and fail.
Additionally without rigid forms that can take some abuse it can be very
hard to get a nice edge as the form springs or pulls away from the pour
a lot when you work it. In my experience the stiffer the mix, regardless
of the thickness of the pour, the more rigid your forms need to be
especially if you dont want voids in the edge when you remove the forms.
We run our concrete as dry as possible and a long plastic tube (say 4-5"
in dia.) filled with sand, cardboard, small sticks and nails, would
never stand up to working and finishing the material.
Next time you get some concrete ask the driver for some stories about
home made forms he or she has delivered to. They are usually quite
funny, 2x4's, plywood, nails, forms are 3/4 full and *whoosh* 6-8 yards
of concrete is suddenly lost in a pile at the base of the form.
> Given that it is outdoor concrete and if it may be subject to freeze/thaw then
> it wouldn't hurt to add a bit of soap to the mix as an air-entraining agent
> which also does double duty in that it enhances the mix's workability by
> helping to retain the water in the mix better, making it a more plastic mix.
Heh, maybe WR Grace's Admix division has it all wrong and they should
just be selling drums of Palmolive rather than SuperP and such ;)
Probably fine for a walkway.
Mark
jeremy
Tony Mugno wrote:
>
> MDF is VERY flexible.
>
You must be thinking of something very different from the MDF that I am
familiar with.
JJ
Mark
>
> Build the forms from strips of 1Z4 masonite, which will bend to the
> radius easily.
Ok, I can't find anything on the web about 1Z4 masonite. Is this the
same thing as the 1/4" or 1/8" hardboard that Home Depot and other
such stores carry?
Thanks
-Mark
jeremy
Lyle is sometimes a little lackadaisical about accuracy, but I think you
will find that he meant 1/4" , and you should really use the type with
the tempered surface.
JJ
Lyle B. Harwood
<nos...@thanksanyway.org> wrote:
€ > Build the forms from strips of 1Z4 masonite, which will bend to the
€ > radius easily.
€
€ Ok, I can't find anything on the web about 1Z4 masonite. Is this the
€ same thing as the 1/4" or 1/8" hardboard that Home Depot and other
€ such stores carry?
Looks to me like I hit the wrong key. I was advocating 1/4" masonite,
and yes, it is the same.
Stake it out, then pile dirt behind it on the outside of the form.
Mark
I think you
> will find that he meant 1/4" , and you should really use the type with
> the tempered surface.
D'oh! Yeah, the typo should have been obvious.
Mark
to build my curved concrete forms for a 4" thick garden border.
I discovered that the spring tension of bent 1/4" masonite is not
too different from a bear trap, so I built a curved jig to hold it in
shape while I stake it in place.
Is there a method I can use to make the masonite
set in its new shape, without compromising its strength?
Thanks
-Mark
Lyle B. Harwood
<nos...@thanksanyway.org> wrote:
€ Is there a method I can use to make the masonite set in its new
€ shape, without compromising its strength?
Drive stakes outside the form, and nail the masonite to the stakes. Use
six penny box nails.
Back the stakes up with a sledgehammer. Note that you'll need either a
third hand or a nail gun. A way to make it easier is to hold the form
to grade, mark the stake, set the level down, start the nail, hold the
form to the mark, and nail.
Note that helpers (usually) come complete with two hands.
Start at one end, work your way to the other, setting elevation as you
go. If you have two fixed elevations, simply run from one to the other.
Backfill with dirt outside the form. You don't depend on the strength
of the masonite, you depend on the dirt.
Cut the stakes off level with the top of the form, to make screeding
easier.
It's easier to do than to explain, which is one of the reasons
carpentry is a trade, taught by apprenticeships rather than a degree,
taught in a classroom.
Mark
What I am wondering though, is whether there is any reasonable
way to get masonite to take a new set? I have a piece held in
place with a jig through a 90-degree bend with a 12-inch radius.
I would like to be able to remove the jig and have the masonite
retain the bend.
Thanks
-Mark
Lyle B. Harwood
<nos...@thanksanyway.org> wrote:
€ Thanks Lyle, that's good detail to add to your previous post. What I
Not that I know of.
Why would you want to do that?
The reason to use masonite is precisely because it's flexible- it won't
hold the bend. The layout is dictated by the site, stringlines, and
plans, not by the material. The material conforms to the site, not
vice-versa.
You drive a stake, nail one end of the strip, (or fasten it to the
sidewalk where you're starting) and move to the next stake- you don't
want the masonite to dictate where the stake is going, you want the
stake to dictate where the masonite is going.
In my experience, it's not important that the radius be twelve inches,
(or thirteen inches, or 24 and 5/8ths inches) it's important that the
grade start where it needs to start, run to where it needs to run to,
that the width is consistent thoughout the bend, and the grade smooth.
Masonite does all those things, but not if you "freeze" it into some
artificial bend that may or may not take everything else (starting
point, ending point, changes in elevation) into consideration.
I realize that it may seem like you want a hard corner, but that would
actually make it harder, not easier.
Try it. Go outside, drive stakes, nail masonite. If the curve isn't
smooth, keep adding (or moving) stakes until it is. You might need to
remove nails and move masonite if you get a bulge, but the masonite
will talk to you, and tell you what it needs. After you play with it
for a little while, you'll see how many stakes you need and where.
Mark
>
> Why would you want to do that?
I'm concerned that the masonite might manage to dislocate the
stakes once I remove the jig. It took a _lot_ of force to bend
it around the jig.
We'll see.
-Mark
Lyle B. Harwood
<nos...@thanksanyway.org> wrote:
€ I'm concerned that the masonite might manage to dislocate the
€ stakes once I remove the jig. It took a _lot_ of force to bend
€ it around the jig.
You cut the masonite into a strips as thick as the pour first. A strip
4 inches wide shouldn't take much force to bend at all.
You put the stakes in the ground, and you nail the masonite to the
stakes one at a time. You have as much leverage as you need by going to
the end of the masonite.
I'm not sure what else I can say, other than to reiterate that this is
a trade, and trades are demonstrated, not taught.
indago
When you get it set to the way you want it, moisten it. Not too much, maybe
a little at a time, until it finally retains the shape that you have it set
for. I have seen masonite board laying against a wall in a basement over a
period of time that finally curved, with the help of the dampness of the
basement, and maintained that shape.
Rico dJour
>There are some architects who like to use burlap sacks to form free-form
>columns.
How is that done? What supports the bags?
R
Mark & Shauna
As an addition to Lyle's info, you could opt to use screws instead of
nails to fasten the masonite to the stakes if you are working alone. A
couple quick clamps can act as third/fourth hands while you are setting
up the forms. Another thing you can try, though I dont know how it will
work out, is to soak the masonite in water for a short time before you
bent it. It may not work well as the masonite may come apart, or it may
not bend in a smooth radius after being wet but you can give it a try.
Lyle is right, there is no need to make the form rigid. However, if you
really insist on doing it that way the only quick way I can think of
would be:
Take a small piece of 3/4" ply, cut the radius you want out of the
corner of the ply, bend the masonite into the radius and screw it to the
ply. You would need one piece of ply cut with a convex radius and the
masonite screwed into it, and one with the concave radius and the
masonite screwed over it (inside and outside forms).
Personally I think its a waste of time but its a way to go if you
insisit on some sort of component based rigid forms that you can carry
to the location.
Ciao,
Mark
Mark
"Mark & Shauna" <n...@no.com> wrote:
> As an addition to Lyle's info, you could opt to use screws instead of
> nails to fasten the masonite to the stakes if you are working alone. A
> couple quick clamps can act as third/fourth hands while you are setting up
> the forms.
Yes, I am considering using screws on the inner form, since the 4" of
space in between doesn't give me much room to swing a hammer.
Although it may work to simply back up the nail head with a steel
dolly and hammer the wood securing block onto the nail point
(I'm using 3/4" metal stakes, so the nails go through the masonite,
then through the holes in the stakes, and into wood backer blocks.)
> Another thing you can try, though I dont know how it will work out, is to
> soak the masonite in water for a short time before you bent it. It may not
> work well as the masonite may come apart, or it may not bend in a smooth
> radius after being wet but you can give it a try.
Good thought. But I decided to stay away from this, since it is likely
to leave me with soggy masonite that doesn't hold its curve well.
Also, as difficult as it was to bend the masonite, it seems to stay in
position just fine with fewer stakes than I expected.
> Take a small piece of 3/4" ply, cut the radius you want out of the corner
> of the ply, bend the masonite into the radius and screw it to the ply.
Yep, I built some tempates that do just that. But it actually requires
through-bolts to hold the masonite in place. . .I tried screws, and they
tore out of the plywood!
-Mark
Mark
"Mark" <nos...@thanksanyway.org> wrote:
> Yep, I built some tempates that do just that. But it actually requires
> through-bolts to hold the masonite in place. . .I tried screws, and they
> tore out of the plywood!
And that was only when I was trying to use a single eighteen-inch-wide
strip of masonite. I have since followed the advice of others and gone to
six-inch wide strips. That works much better.
-Mark