I want to build a 1/2 round portico foundation.. Rather than just a few sono tubes full of concrete I want an actual concrete basement. Other than a whole lot of custom form work are there any simple (and here’s that wonderful word, CHEAP!) ways to do this?
I know of No ICF that is for the round nor can I imagine any at a shallow enough angle to make a round foundation..
please correct me.. or come up with simple and Cheap way to build form work..
Replies
Did you check with a form outfit to see if they have curved form sections at the radius you need? If not, it sounds like you're going to have to frame the inner and outer forms like curved walls, and laminate say, three layers of thin (3/8) ply onto the 'studs'. Then position them face to face and drill 'em for wire-ties. I can't think of any other way to do it.
Wait a sec: You oughta check with Cloud. If anybody knows about curves in concrete, it oughta be him....
Dinosaur
A day may come when the courage of men fails,when we forsake our friends and break all bonds of fellowship...
But it is not this day.
There was just a discussion on forming a half-round wall about a week ago...lots of good ideas.Dino, we almost never do basements, so our formwork is limited to 2' or 3' high round footers. Different than 8' or 10' high, which the other discussion covered well.
Frenchy
What radius are you thinking about? That might have some bearing on ideas.
Doug
What about blocks? Filled and with rebar?
I've seen a couple of porticos done like that.
When in doubt, get a bigger hammer!
Blocks really wouldn't work. no way to get them to the front yard except carry them, too many to carry.
with ICF's I can pump the concrete thru the basement.
lol, thats why you hire a grunt!
When in doubt, get a bigger hammer!
DougU
a ten foot radius would work although I'm actually using an 11 foot radius I could cantilever it the foot)
ICF's can be kerfed and bent quite easily. We used a brand called Quadlock and bent them to form walls with 3' 8", 8', and 12' radius'. Kerf every 2" about halfway through the 2" thick panel.
Wood is Good
Adam Greisz
Adam Griesz,
do you have a web site for them?
Here is a link to Quad locks web page. http://www.quadlock.com/
Pretty easy to curve them but lots of cutting kerf's in foam. They recommended a hot knife but that was killing our guys with fumes. Ended up just motoring a skillsaw over a jig. Still melted the foam but just a little bit.Wood is Good
Adam Greisz<!----><!----><!---->
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Sometimes an electric knife works well for cutting foam.--------------
No electrons were harmed in the making of this post.
frenchy,
I have a spare CD from Integra-Spec with a formula for cutting forms to produce circular walls. Do you want it? I could probably even email you the relevant section if you're in a hurry but you would want the rest of the Integra spec manual for background, I think. That's available online.
I have never formed a round wall with ICF and have no idea how much work it is. An Integra Spec trainer from Ontario told me it was dead easy, but slow.
Ron
frenchy, with all that native lumber you have stacked around, I wouldn't think it much of a problem to build curved forms - just take some of that walnut and reinforce it with cherry, brace it with white oak and pump away -
"there's enough for everyone"
David,
I knew as much and as cheap as those timbers are I still hate to waste them. Sad to say that I have in the past and now instead of having many timbers to choose from I've got just enough with none to spare..
The sawmill won't sell me any more black walnut at 17 cents a bd.ft. and even white oak is up to 60 cents a bd. ft. Sure, I can buy red pine for 40 cents but I was hoping for an easier way. This summer I made forms with some Hard maple that I'd let get wet and it had spalted, 85 cents a board foot and it wound up in the dumpster.. thus I paid twice for it. Once to buy it and once to throw it away. 18 to 22 inch wide flawless all white hard maple boards and they wound up in the dumpster. I tell you that really hurt for a tightwad like myself..
I've certainly seen curved forms built with Masonite or something similar.
No electrons were harmed in the making of this post.
We did that for all of our curved sidewalks. For the house footer we used 2 layers of 1/4" OSB. Choice would depend a lot on height of pour be/c of hydrostatic pressure.
Frenchy,
Cloud is right, there is no reason at all why you can't build these forms yourself.
A few layers of plywood, cut radiused walers out of dimensional lumber or engineered (like LVL) lumber, use regular old snap ties, and off you go.
Calculate your form pressures as density of concrete x height of form, so if you have (for example) a form that is one foot wide, 10 feet high, and your concrete is about 150 pounds per cubic foot, you need to restrain 1,500 psf at the base.
NOTE TO NIT-PICKERS: THIS IS AN APPROXIMATION TO KEEP PEOPLE FROM GETTING HURT. I KNOW THAT THIS IS NOT ACCURATE TO A FEW DECIMAL PLACES> <G>
If you really need to figure this out to the nth place, consult ACI 347.
EVEN MORE IMPORTANT SAFETY NOTES:
1) Remember that fluid acts in all directions, that means uplift too. Secure the form to the footings so you don't float them. This makes a mess, trust me.
2) This does NOT include a safety factot if you intend to vibrate the concrete. If you don't know what you are doing with a concrete vibrator, you are better off without it. Improper use can weaken the concretet and blow out your forms.
3) You can dramatically reduce the necessity for overbuilding the forms by adjusting your pour rate.
The formula I gave above applies to liquids, concrete is not a liquid soon after placement. You can pour in lifts working around the forms slowly. That will help.
As the concrete stiffens in the forms, each sucessive lift exerts less pressure than if you poured it all at once.
If you trust your pump operator, you can also batch with an accellerant.
Edited 10/10/2005 2:16 pm ET by Catskinner
For some reason the company that I framed for got called upon numerous times to form curved wall.
Do not cut radius whalers as was sugested.
Do cut radius top and bottom plates (from plywood). You can use snap ties or quick strip ties. but run the whalers vertically. if using steel whalers you will have to drill holes in the top plate so that you can slide the bars down into the ties. 2x4 whalers with snap ties are kinda easier. but is harder to button up with the ties so it is a trade off. the quick strip ties you can slide in thru the holes after you have closed up. also you don't need 3 layers of ply.. 2 layers of 3/8 will be fine.
a few years ago I also got called in to do some back framing on a house with a basement room that was poured as part of the foundation. it had a radius of about 10' and was formed with something I had never seen before. it was made of a hard plastic type material. I'm not sure if it was prefabbed to suit or bent to shape on site. it was about 10' high. As I remember it it had flat sort of sections maybe 6" - 10" wide so that it sort of had a hex look to it.I wish I had more info about what kinda product it was. Buty anyways you certainly will be able to form it yourself.
"Do not cut radius whalers as was sugested.Do cut radius top and bottom plates (from plywood). You can use snap ties or quick strip ties. but run the whalers vertically. "Great idea -- thanks. I'll be using that one.
use Gates form hardware and two layers of 3/8" sheathing. The sheets lay down ,Gates hardware will give you the drilling specs for their ties.Gates hardware is usually done with 3/4' ply and the sheets stand up on the 4'-0 edge. for circular work the opposite works better. Cut templates for the inside and outside radius plates.I use a router on a long trammel for the templates. Make sure you take in account the 3/4" thickness when routing the templates. Make just two,inside and outside. Then use these for the rest of the plates without the trammel. Use a top bearing bit with the templates tacked on top. The outside forms have to be made in panels so they can be handled.When excavating leave plenty of room on the outside to set the panels. Unlike straight walls that can be tipped up to connect the ties,circular walls have to be walked in fairly plumb from one end.If you are familiar with the gates system, ,this is an easy job. If not ,see if there is a carpenter near you that is familiar with the system. Two experienced carpenters can do the entire job in less than 2 days.
mike