Hello:
I just received the quote for my crawl-space ICF foundation, $15,700. The crawl-space is directly on sloping bedrock & will have an average height of 4 feet. I find it very expensive but, I do not know.
It seems that the 10 corners really drive the cost up.
So, I am wondering about cantilevers, supported by posts, which are in turn sitting on footings which are pinned to the bedrock.
My major concern is the inside floor temperature of the bump-outs - is there a way to build the cantilevers so that they stay warm. (80 miles north of Montreal QC - 9,200 HDD)

Here is a quick drawing showing the house foot-print:



I am getting very discouraged. Maybe I should scrap the ICF's, that alone costs $4,400 including re-bar.

Thanks for any input.

Rob.

Footings included?

Yes

Doesn't seem too bad to me.

Thanks ICFHybrid.

My disappointment lies in the fact that I will be paying $15,000 for a crawl-space where 25% is 2 feet high, 50% is 3 feet high and the balance is 4 to 5 feet high.

I was hoping for a less expensive solution.

Like I said, I may for go the ICF's and just get a concrete foundation done & then glue foam the the inside.

I still have to spray-foam the actual bedrock floor at a cost of about $2,800.

I guess that's the price you pay for building a house on bedrock.

Rob.

If you want the crawlspace higher, can't you just add another course of block around the entire perimeter?

what is the linear footage of the foundation walls?

The linear footage is 165.

My foundation contractors charge about $40-45 per linear foot for frost walls. Obviously adding reinforcing and stepping the footings up & down, pinning to ledge will increase the cost somewhat, but that's still half of your quote. i realize that costs may be quite different in your area, so that might explain part of it. have you had anyone quote a standard 8" x4' concrete wall?

Hi Bob:

Yes, the quote for a standard 4'x8" wall was $9,500.

I can reduce the number of corners from 10 to 5, if I use cantilevers to build the bump-outs:



This would require only one 4' x 7' 5" cantilever to accommodate the 'mud room'. (Top, left-hand corner)

i think you can do a pretty good job of insulating a concrete wall fora good deal less than $6200.

Yes Bob, I think that I will 'turf' the ICF's.

I would prefer to place the foam on the outside of the foundation but my 'mutineer' is concerned about the time and expense of covering that foam.

I was thinking 'cement board'???

The cement board must be approved for use below grade. Some"cement" products, like hardi board, do not react well being immersed in water and will disintegrate. covering the foam with a cement coating and/or cement board does take time, but would be time well spent. You could glue the board on with adhesive, but be sure if you use the board that the seams are taped or filled with foam friendly caulk.

Why such odd dimensions on your foundation? 30' 9 1/4", 10' 8 3/4" ? If you would stick with exterior dimensions in 2', 1', or even 8" increments it generally results in reduced waste and less cost.

What's going on top of the wall. One or two stories? You don't need a 8" wall even if a two story, a 6" will be more than enough. By my calculations you have a little under 152 lin ft. Would be about $8,000 down here in NY.. I did one like this in the Adirondacks three years ago The thing that saved a lot of time was puting the long walls together to 3 course height, then leveling the wall and using a set of improvised dividers to scribe the forms from long to short. Cut each side of the form with a circular saw. I also mono poured the footing and walls in one shot which saved time and cost on the pump. We laid down reclaimed xps and shot a rat slab over the top to insulate the bed rock.

Hi arkie6:

Sorry about that - here are the correct foundation dimensions - 163 LF, outside:

Thanks smartwall, sure wish that you were here! :)

It is a single-story house. The walls are made with 2x8's 16 OC so that I can use Roxul R-28 ComfortBatts. see: Double-Wall mutiny post.

Rob.

Maybe I'll travel North. The reason I asked about what was going on top, is the prescriptive metod allows 3.5" walls for what you are building. You would need more vertical rebar. I just looked at the PM and 6" would be the way to go. #4@48" pinned thru the footing and continuing into the wall would give you a great tie to the bedrock. Not sure what your icf cost are but at $3.5 per ft down hear you would need 650 sq ft at 4" height all the way around for a cost of about $2200. Fooling around with regular forms for this project is crazy from a labor stand point.

Hi smartwall:

If you 'travel north', bring your own ICF's!

 A 8"x16"x48" ARXX Prime ICF costs $27.00 here - $6.75 per foot.

Cement costs about $150 per cu. yd.  Re-bar: 1/2" x 20' costs $5.97

I just got a quote for a 'cement-only foundation', on footings: $10,900 including tax. (The ICF quote was $15,700 including tax.)

Rob.

My 3' icf frost wall cost roughly as much as your bid, and I had 11 corners, multiple steps to reach undisturbed soil, a radius and a bit more wall length. Foxblocks has a "project estimator" on its site of the same name. Menards.com, a building supply box store in the midwest, sells Fox blocks online. You can also deal directly with Fox blocks in Omaha, NE. You'd pay shipping from Nebraska in either case. Your contractor may be counting on some markup in the Arxx blocks, but presenting him a cheaper alternative still improves your bargaining position. Hopefully you haved more than one icf contractor in your area.