What is the lowest cost way to form a reinforced concrete wall with a radius of 25 feet for a walkout basement.  To picture this, think of a house in the shape of a circle made with structural concrete walls.

I know a curvy wall can be formed with Spider Ties but I do not know about cost just yet.  http://spidertie.com/   Does anyone have experience working with Spider Ties they can share with me? 

I also know that a curvy wall can be fomed with ICF's but the cost may be beyond budget.

You can use plywood forms and poured concrete. Or blocks + stucco.

Icf. I did a curved underground baseball court in Syracuse NY in Nov. The foundation contractor said it would have taken twice as long and twice as much to do it. It was 16.5 ft high. very simple to make curved walls with icf.

Spider Ties are really expensive when you put the pieces together with the plywood forms. Nudura ICF is easy to make curved walls with since it has a hinged pin system, I make my own curves. Cost wise because of the cost of spider tie ($1.50 per 6" piece) adds up really fast...and it's the same material as an ICF web. your ICF will be under $4.00 sq.ft.

Now if your not planning to finish the outside of the wall, maybe the spider tie would be the way to go, but I would call the ICF manufacturers first and see if they will sell you just the webs, be cheaper. I did this many years ago and ARXX sent me defective webs...which suited me fine for what I was doing.

Thanks to everyone for their replies.

Chris, installing ICF appears to be less work than using Spider Ties.  The part of the basement wall below grade will not be finished.  The part above grade will have man-made stone.  If the stone is light enough, then we may not need a ledge to support it.  At this point in time, I do not know if the stone can be adhered directly to the EPS forms or if wire mesh will need to be screwed to the plastic webs.

One big disadvantage for a Spider Tie below grade wall is that every tie location will have to be taped and muddied to avoid leaks.  At least that is what I saw in a video. 

How do you make curved walls with Nudura?  Does the hinged form lend itself to making curves or does Nudura require saw kerfs to bend the form to meet the circle?

Smartwall, what brand of ICF did you use and how did you make curves?

I have seen one ICF that has corners that can swivel to any angle.  I do know if they can be used to follow a circle.

Posted By Alton on 22 Feb 2013 05:37 PM
Thanks to everyone for their replies.

Chris, installing ICF appears to be less work than using Spider Ties.  The part of the basement wall below grade will not be finished.  The part above grade will have man-made stone.  If the stone is light enough, then we may not need a ledge to support it.  At this point in time, I do not know if the stone can be adhered directly to the EPS forms or if wire mesh will need to be screwed to the plastic webs.

One big disadvantage for a Spider Tie below grade wall is that every tie location will have to be taped and muddied to avoid leaks.  At least that is what I saw in a video. 

How do you make curved walls with Nudura?  Does the hinged form lend itself to making curves or does Nudura require saw kerfs to bend the form to meet the circle?

Smartwall, what brand of ICF did you use and how did you make curves?

I have seen one ICF that has corners that can swivel to any angle.  I do know if they can be used to follow a circle.

Chris - how do you calculate how much to cut out of the inside face?

Depending on how tight the curve is dictates if and how many kerf cuts are needed on the inside of the exterior panel. Nudura has a calculator for how much needs to be removed from the inside panel.

I prefer making my own curved with Nudura as the hinged pin allows the pieces to be moved easier to allow the kerf cut. You can also order from them pre-cut, they come with the slide in webs which requires assembly on site. Either works fine but with fabricating myself I do not have to wait for special order.

They also produce a brick ledge extension that can be incorporated if needed.

I used to do the interior cut. My Fox Block rep. suggested cutting the outside of the block and making kerf cuts on the inside. This is what we did on this basketball job, what a difference in time spent trying to figure out the curve and how much to cut. I've used the interior cut formula that Build Block has in it's installation manuel, but this method blows it out of the water as far as time. All you do is foam the cuts and strap the outside. Very quick and easy

Smartwall,

Are you saying that you cut the EPS completely through on the outside and then cut kerfs on the inside EPS?  Were the kerfs on the inside EPS only the width of the saw blade or were the kerfs a V-notch that removed some material other than the sawdust?  About how far apart were the cuts on the outside?

The outside method does work faster on a fixed block, the issue I found is additional strapping is required as you have weakened the form a lot more. But again it's easier to kerf the outside on a fixed block. Also keep in mind the wall is not really curved with an outside cut, you have created a whole bunch of flat spots so if your planning on stucco it has created additional prep/base coat for the installer to round the wall. If its brick with an airspace it's a non issue.

Fox makes a curved block, but your design has to meet their standard curve sizes, the pieces are only 16" long, I believe they said the length was chosen because of shipping, it required lots of strapping. We did it as they suggested with minimal bracing, I'm glad it was below grade, when we did the upper walls we strapped the living day lights out of it.

This may be a little far out. I am not sure of the engineering. Check out concrete fence methods on Monolithic Dome.com. Engineering needed to tell you depth of concrete and reinforcement. Tie the reinforcement together to form a supportive layer. Place recycled billboard tarp against 1 side, spray concrete against reinforcement. Remove tarp when dry, spray other side. You may want CMU pillars every 8 feet or so to establish the curve and support the rebar framework. The following link shows a similar process used to form a whole dome; a vertical wall should be much easier. http://www.mortarsprayer.com/thin-shell-construction/thin-shell-garage-dome/

We cut the block all the way thru on the outside and 2, 1 inch deep kerfs between each web on the inside. The kerfs were the width of the blade. We used some questionable Chinese luan plywood cut into 6" strips to band the outside. I used a collated screw gun to fasten the strips. It took about an hour to strap. As far as gaps in the wall surface, thats what they make foam for. Any extra was sawed off and rasped. As I said I've done it the interior cut method, but would use this method again if another job required a curved wall.