I'm laying out an ICF foundation and have two questions I'm sure others have dealt with before. First, I have a masonry chimney which I would like to place right against the interior face of the concrete. Is there an easier way to do this than to pour the ICF wall and then strip the foam (and ties) off after the pour? Is there a way to face one side of the wall with plywood with ties through to the other face? The second question regards pouring pilasters. I will have a 6" wall for most of the foundation however one 25' section needs to be 10" to receive wind bracing steel. The steel will be a 14" W Section so I need about a 24" wide pilaster at each end of the wall and one in the center - so about 6' out of 25' total. My concrete here is about $225/CY so I'm wondering if I should just pour the whole wall at 10" (adding about 3 CY or $800) or if there is an easy way to form the pilasters? By coincidence, the center pilaster will be the area that backs up to the chimney in my first question so I may be forming and stripping that anyway. Have not decided on ICF yet but likely to be Integra Spec, Logix or Nudura if that makes a difference. Thanks!

On the chimney: is there a problem with having some foam in between the concrete and the masonry? You might even want it for insulation purposes.

For structure, you can cut away just a portion of the form where it meets CMU and patch with sheet goods like ply or OSB.

Have you settled on which system you plan to use for this project?

Since the foam is combustible I'd need 2" clearance per code between the chimney and the foam which would put the chimney 4" further out than I want it (2" foam plus 2" clearance. To maintain the R value I can always put a sheet of XPS on the exterior side prior to back filling. I'm wondering if there is an easy way to form pilasters with ICF's or do I have to just plan on lots of carpentry to hold the forms together. Brian not sure on the Brand. Logix has good support here but Integra and Nudura both ship flat and shipping is a big expense for me. If I had to guess right now though - I'd guess Logix.

Logix has pilaster forms for 16" pilasters. You might be able to cobble two together to get the 24" but you'd have to use sheet goods and bracing liberally across the joint.

Is your chimney the old-fashioned flue-containing kind? I have a masonry chimney, but it contains EPA sealed fireplaces and double-wall vent pipe.

Stripping a lot of foam is yucky. You don't do it a second time. Although, it is a good job for a laborer. Not much they can hurt.

Posted By Birdman on 27 Aug 2012 12:26 PM
I'm laying out an ICF foundation and have two questions I'm sure others have dealt with before. First, I have a masonry chimney which I would like to place right against the interior face of the concrete. Is there an easier way to do this than to pour the ICF wall and then strip the foam (and ties) off after the pour? Is there a way to face one side of the wall with plywood with ties through to the other face?

How high is the foundation? If it's only a couple of feet I think stripping aftwards would be easiest. Ties should be easy to whack off with a hammer & chisel. If the concrete can extend even with the inside of the blocks I'd look at forming with plywood. It's easy to cut the foam and ties out before you put concrete in the forms. Just fasten the plywood with wires from the outside to the ties. Or, just put an additional brace or two against the plywood.

I wonder if you may be over thinking this situation, unless you're building a 6' wide fireplace against an 8' high foundation wall. That would be a little more involved.

What area are you in? Quad-Lock makes Pilasters quite easy to form (see link) http://www.quadlock.com/images/engineering/ICF_Pilaster_Detail.png

There is no doubt about the fact that freight costs are through the roof right now, but don't choose a system just based upon the location. The fact that you are looking at who has good local support is smart! If I can help direct you to a local Quad-Lock guy I would be more than happy to, pardon the brief sales pitch..

The foam of (almost) all ICF's is not combustible. There are flame retardants mixed in with the foam bead, a mapp torch taken directly to the foam will cause it to melt, but will not support a flame. The only concern you would have with a chimney on the foam would be melting, but that could be properly designed to work.

Stripping the foam is a mess, as Hybrid said. It can be done, but I would do all that you can to avoid it!

What are your other top plate heights?

Thanks all. The wall is a full foundation wall - 8'-8" tall. Chimney footprint is 3'-0" x 1'-8" with the long side against the foundation. The first floor is a slab on bar joists with radiant in it and the framed wall above the slab is a double stud (7") wall. I may be over thinking this - it may be easiest to just form that 3' section in plywood and wire tie through the wall - it's only 3'. I just thought there might be some super slick wheel someone has already invented. In delving into the installation manuals for various ICF's I see assorted ways to handle pilasters - none look real easy but all seem doable.

I'm in Rhode Island - actually 12 miles off the coast Rhode Island - which is why shipping is an issue - it has to be shipped on a real ship! The freight charge for a tractor trailer over 7 feet tall is $5.60 per lineal foot length over all (includes cab) each way so that adds up. It is usually cheaper to ship pallets if it can be palletized.

Run a line through all the ICF blocks and tow them over. I'm kidding....

Does the chimney have to be masonry?

Pilasters are easy just mix in !0" or 12" thick forms depending on how thick you want the pilasters to be. Birdman send a PM

I have a strong preference (visually) for the masonry. I LIKE the towing idea!! perhaps strap them together and hang an outboard on the "stern"!!

You can put natural stone on a wood frame chase. Can't tell the difference from the outside. I shoulda done that.

Your choice of integraspec is a logical one.

We have built many pilasters with their icf.

The trick is to size the pilaster larger than needed and still working with the webs for support. No additional bracing is need.

They have a great slide show on the website www.integraspec.com

Thanks Eldon Howe

www.totalicfs.com