Does anyone have experience with dry stacking Cinder blocks

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  #1  
Old 04-18-18, 02:03 PM
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Does anyone have experience with dry stacking Cinder blocks

I need to build a crawlspace foundation out of 12" cinder blocks. I have read online you can use mortar for the first row only at the bottom and for the last row (5 high) and then fill them with concrete. I find conflicting information about this on the internet and I was wondering if any one has any experience with this or maybe want to share their opinion on this subject
 
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Old 04-18-18, 02:16 PM
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Is this a new build or are you underpinning and existing structure?
I would assume that method would be plenty strong enough providing you use rebar in some of the voids but IMO it would be easier/cheaper to just mortar the block and then add concrete/rebar where needed.
 
  #3  
Old 04-18-18, 07:23 PM
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Rudolf -

The construction you are suggesting could be considerably weaker than conventional masonry construction with face shell mortaring.

You cannot use mortar to fill the cores. You need to use gout (8" to 11" slump) to get good filling - It could possibly be be strong enough for your loads, but is not reliable. If you bother to look at concrete the heights are not always accurate. The ASTM height specification allows a 1/8" variation, so the block will rock as you stack them and the wall will be weaker than conventional masonry. There have been many "dry-stack systems in the last 50 years, but the only successful ones used block that were dimension ground for uniform height. - The block were about $0.25 to $0.50 than conventional block.

Filling a 12" wall will require a lot of mixing on the job site in addition to sand and cement and the labor.

Dow gave up on using and caulking gun to replace mortar because of the cost of getting extremely accurate masonry units.

There is a very old question - "Does mortar hold the block together or keep them apart?" - The answer is that it allows you to build a truly vertical wall to the height you want.

Dick
 
  #4  
Old 04-19-18, 06:20 AM
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Thank you Dick for you answer. The filling of the blocks would be with 5 bag concrete mix and would be pumped in to the hole (brought in by truck). But I git some answers from people around me to and I think I will go the mortar way.
 
  #5  
Old 04-19-18, 08:42 AM
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Concrete mix is not adequate because of the larger aggregate size - It does not fill all the voids and you can have voids. It will also take longer to fill.

Grout does not have the coarser aggregate sizes and can fill better than concrete since you probably will not have a good way the vibrate the mix into the voids.

Mortar is not adequate because of the excess of sand and difficulty of completely filling the cores.

Any good concrete supplier can supply grout in the same trucks. Some can even pump it to avoid tearing up lawns, curbs and driveways. Based on the small amount, they may charge a "short load" surcharge.

Have the "people" around you do it and give you a long term guarantee. - There are actually codes and specifications for things like mortar, grout and concrete and they are all different. If you are happy with what you are going to live in for a few years and then sell. There are actually different ASTM standards and code specifications describing what mortar, grout and concrete are.

Dick
 

Last edited by Concretemasonry; 04-19-18 at 08:43 AM. Reason: grammer
  #6  
Old 04-22-18, 05:55 AM
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steel reinforced grout-fill'd columns every 2' - balance of cores filled w/grout - we use 12,000# - ( eg, 5star - no $ interest ),,, as dick sez, no conc - aggregate will prevent total interlock,,, remember to vibrate sufficiantly
 
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