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I am a building inspector in the Cleveland, Ohio. We recently had a contractor rebuild 2 walls of a basement by dry stacking 12″ hollow cement blocks. Although I have nearly 25 years in the trades I have never seen this done before and our local ordiances do not permit this type of construction. I’m looking for someone who has experience with this type of foundation for some do’s & dont’s type guidance
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Mark,
The dry stack method is stronger in shear and right at the same strength in compression as a mortared block wall, if the appropriate coating has been put on both sides of the wall (all other wall specifications being equal). This is a modified cementitious coating with fibers in it that bridge the joints. "Quick Bond" is a brand available here.
There have been articles in FHB on this construction method (LONG time ago) and block plants in my state (Wyoming) have the necessary products and information for use. Also, the Concrete Masonry Association has information/specifications for dry stacking and they have engineers that will answer questions.
*Thank-you Mike I will check on those references
*Hi Mark,If you have a local Home Depot store, go there and look in their books section. Get the book titled "FOUNDATIONS & CONCRETE WORK" by Fine Homebuilding's For Pros/By Pros. (Large paperback style...green cover with photo of guys working a concrete pour)This book is a collection of articles previously produced by Fine Homebuilding. A very good article about surface bonding dry stacked block is on page 126. There is also another good article about a different type of dry stacking (using precision ground block)that's being used out West. That article is on page 112.The book is only $15.00 and is a good useful reference tool.An older version of this book by Taunton Press was formerly titled "FOUNDATIONS & MASONRY" which contains both of the above mentioned articles as well.I used this concept when building my detached garage. I poured a floating slab, then laid down 2 courses of 8X16 concrete block. I used an approved adhesive for my bottom course, though most use regular mortar to bond the initial course. The second course was stacked on top of the first course. I used galv brick wall ties as shims where needed to keep the 2nd course dead level. The block is stacked "tight" no spaces between joints. I used a commercial product called "B-Bond." Other trade names is "Fiber Coat", "Quick Coat", etc. It's basically a cement mix reinforced with chopped fiberglass embedded in it. The reason the block must be stacked tight is to permit the fiberglass to "span" across the joints and hold the block firm. Too large of a gap, and the fiberglass cannot span, and your block has no torsional strength. Compressive strength is actually very strong (Block on block, no bad mortar mixes in between to weaken compressive strength). Coating must be on both sides of wall. Coating is only to be 1/8 thick. Little thicker (1/4 inch) won't hurt anything. Coating must cure similar to concrete and should be allowed to moist cure for a few days.When dry, the coating itself is waterproof.My wall was only 2 courses high. I built a wood framed garage on top of this foundation wall. Every 4 feet, I had 1/2 inch all thread embedded into the concrete slab, and I filled the concrete block cells with concrete at these locations. The all thread became my plate anchors for my framing.If you get the book, you will see that, when used for basement walls, it is recommended (perhaps required?) to install pilasters on the inside of the bsement walls at intervals of every 18 feet for 12 inch thick block walls. These pilasters should have threaded rod or rebar in them, and be fully filled up with concrete.Please know that coal mines used this block wall technique in deep mining for many years. If done right, it is a very STRONG wall.Good luck in your search.Davo.
*Thanks Davo, I can see using this method above grade. Our concern here is below grade subjecting to hydraulic pressures. This contractor failed to ask for any inspections to verify reinforcing, pilasters, or other methods required to support this house. The old block walls were pushed so far in that replacement was necessary! We are concerned with the freeze / thaw cycles we experience here in Cleveland and so far the only info I can find for these walls is above grade and it seems to be more out West. The contractors claim regarding the pyramids being dry-stacked doesn't convince us that it will endure the same as hollow CMU's in Ohio!!! I will stop @ HD for the book.... Thanks again I appreciate eveyones help.
Do you think this material would good for waterproofing a very good garage concrete floor? I'm converting it to a woodshop and don't want to add much thickness to the floor
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I am a building inspector in the Cleveland, Ohio. We recently had a contractor rebuild 2 walls of a basement by dry stacking 12" hollow cement blocks. Although I have nearly 25 years in the trades I have never seen this done before and our local ordiances do not permit this type of construction. I'm looking for someone who has experience with this type of foundation for some do's & dont's type guidance