Replies

1. 
   hopefularchitecture | Jan 08, 2019 11:28pm | #1

   why support the concrete industry? nothing green about that. boring bricks are going to be available soon.

2. 
   Peter Yost | Jan 09, 2019 11:37am | #2

   Hi Mike -

   I am not sure what you mean by ICF dry stack blocks--can you say more about the system? Do you mean dry-stacking standard concrete masonry units (CMU)? Where would you locate the "recycled foam?"

   Best - Peter

3. 
   mikeysp | Jan 09, 2019 11:58am | #3

   Hi Peter!

   I am indeed talking about CMU Concrete Blocks 8"x8"x16"
   As to location of foam, I am unsure. I imagined both sides of the concrete blocks, right up against it and then to put vertical 1x4 or 2x4 for siding and drywall.

   The reason I used the words ICF and dry-stack was because I envisioned the same "look" concrete blocks sandwiched with foam.

   Since I had not seen much of people going this route, I thought I might be wiser to stay the standard plan that I had of using 2x6 advanced framing with a foam board on the outside for a thermal break.

   The dry stacked techniques "appears" simple and since I can recycle leftover jobsite blocks that I can get for 50-75 cents a piece, it might be a good idea. Not sure how to evaluate it since I am having trouble identifying folks who have done it and reviewed/critiqued it.

   I thought the lack of examples might be because ICF walls are much faster to put together, and this means a huge savings in labor costs. In my case, I see my labor as free, even though it is not in reality.

   But, I do still want to evaluate the technique, so I can make an informed decision. While my time is free as I see it, I sure don't want to double my construction time or cost for that matter.

   I hope this brings enough clarification.

   -Mike

4. 
   onslow | Jan 09, 2019 12:49pm | #4

   Mike,

   I can't find the specific reference in my files, but I do recall entertaining similar thoughts when working through earlier designs that I did not follow up. The type of wall (dry stacked cement block) you have described is, I believe, stacked then coated with a fiber re-inforced parge coat on both sides. This is what ties the whole stack of blocks together. I am pretty sure that rebar and concrete fill was also required at set distances along the wall length. It it also a pretty sure bet that some form of top beam would be required as well for exterior walls. The lateral strength of such a wall without the extensive rebar and filled cells would be questionable for any usage other than interior walls.

   You are correct, the surface must be very, very true or the stacking has two ways to go willy wobble quickly. True you can set the first course in a thinset like bedding, but it was never clear to me how one would account for variations in the blocks themselves. Even using a laser would make such a wall tedious compared to standard block and mortar. Add in the problem of dealing with load distribution around openings, secure roof element attachments, window details, electrical wiring, etc: you can perhaps see why I took a pass on the whole idea.

   Not exactly clear on what you mean by "All back-fill 8″ below slab surface", but remember that in your mixed humid environment, all masonry elements can become moisture reservoirs as drying to the environment will be limited by the humidity. Walls of CMU might be a less than ideal choice for a number of reasons. Personally, I would first work on making sure the slab is isolated from the ground for thermal and moisture inputs as aggressively as possible, ie: at least R10 under slab (more better) a pea stone bed under that and properly set footing drains to daylight if possible, a down slope wet well if the lot is flattish. Framing with wood I believe will save you much grief. Way more to consider after that. As you already know, keep reviewing the GBA resources for best handling of framing, exterior insulation and rain-gapped siding details.

   There are of course several dozen other points for discussion about windows, floors, roof, siding, insulation, heating, lighting, ventilation, and so on. This is not to suggest you can't do your own build, just a caution to keep reading GBA and try your best to understand the reasons behind why choices are made. It will be easy to find people that tell you "I have always done it this way" during a build. Unfortunately, that doesn't always mean they were doing it right. Best of luck and give yourself time to start making your list of informed choices as you develop your building plans.

5. 
   mikeysp | Jan 09, 2019 03:07pm | #5

   Hi Roger! Excellent response. This was exactly the type of info I was looking for: how to think it through, evaluate the feasibility. You bring up many excellent things to consider and be aware of. When I stated:"All back-fill 8″ below slab surface" I was just providing the info my inspector said would be relevant to a structural engineer to evaluate my idea, as a wall that is subgrade would have backfill pushing in on the walls. In my case, this would not be.

   Again, thank you for the very helpful response. -Mike

6. 
   natesc | Jan 09, 2019 03:29pm | #6

   I've laid a fair amount of block and can't imagine doing it without mortar. Blocks have lots of imperfections, and the mortar is your shim. The fiber parge coat might even make it more expensive than just using regular S mortar.

   Above grade you are way better off just stick framing either way.

1. 
   mikeysp | Jan 09, 2019 03:36pm | #7

   Thanks for that important note Nathan. I think I am going to stick with my plan to stick frame. Thank you gentlemen for helping make the decision.

7. Expert Member
   MALCOLM TAYLOR | Jan 09, 2019 04:14pm | #8

   Mike,

   One of the advantages of ICF construction is that it gives you attachment points for finishes on both sides. With CMU construction, whether dry-laid or not, you are left with the problem of attaching the foam, and also all the finishes to the blocks. To me that would negate any advantage you gained.