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  #1  
Old 06-04-2014, 08:55 AM
Peasant
 
Join Date: Mar 2014
Location: USA
Posts: 48
Default Aggrevating Variation in Block Size

Several days ago, I began dry stacking my block. All of a sudden I realized that my block had a good deal of variation in height. They should be 7 5/8" tall, but some of them are from 1/4" to 3/8" taller than they are supposed to be!

There is also surprising (to me anyway) variation in the other dimensions. Some of the block are not square top to bottom - and sort of lean out or lean in.

Needless to say, the stacked block look bad...with big gaps here and there. I always thought concrete block were more uniform in size.

Is this a common issue?

Should I try to fill the gaps with mortar before I pour the cores?
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  #2  
Old 06-04-2014, 09:31 AM
Tscarborough's Avatar
Il Pizzaiolo
 
Join Date: Oct 2009
Location: Ausitn
Posts: 2,990
Default Re: Aggrevating Variation in Block Size

Now you know the purpose of mortar. Those dimensions are well within standards for CMU, although the slumps units sound pretty crappy.
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  #3  
Old 06-04-2014, 09:32 AM
Journeyman
 
Join Date: Jan 2014
Location: Western North Carolina, USA
Posts: 324
Default Re: Aggrevating Variation in Block Size

If you can live w/what you have, you can always adjust your formwork for your hearth slab to be square and level. Once the slab is poured and is square and level, the block work won't matter. Just be sure to fix it at that point and not let it go. Unless the block is real bad, it should just be a few minor adjustments to your form work to get it right, in my opinion.
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Last edited by NCMan; 06-04-2014 at 09:35 AM. Reason: Typo
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Old 06-04-2014, 11:23 AM
david s's Avatar
Il Pizzaiolo
 
Join Date: Mar 2007
Location: Townsville, Nth Queensland,Australia
Posts: 4,687
Default Re: Aggrevating Variation in Block Size

If you chip off the little dags on the bottom of the blocks you will get a more uniform size. If you are not mortaring between the bricks an alternative is to use a masonry adhesive and some 5/16" washers placed at strategic places will keep the work level. The first row of bricks should have a bed of mortar between them and the foundation slab.

Last edited by david s; 06-04-2014 at 11:26 AM.
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  #5  
Old 06-04-2014, 01:23 PM
Peasant
 
Join Date: Mar 2014
Location: USA
Posts: 48
Default Re: Aggrevating Variation in Block Size

In the past, when I've used block before, I believe they were much more uniform in size (and squareness). Yes, I understand that is one of the purposes of mortar.

But if I have a block 1/8" short and the next block is 3/8" tall, that is a 1/2" variation causing a 1/2" gap, and would look rather bad even if mortar were being used between the block.

As all of this will be covered in a yet-to-be-decided finish, I'm not really that worried about it...just aggravated.
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Old 06-04-2014, 07:12 PM
Tscarborough's Avatar
Il Pizzaiolo
 
Join Date: Oct 2009
Location: Ausitn
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Default Re: Aggrevating Variation in Block Size

I didn't say they were GOOD block, just within tolerance. If I put those CMU on a job, I would not be selling many block.
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Old 06-04-2014, 07:34 PM
Apprentice
 
Join Date: Dec 2013
Location: Wisconsin
Posts: 108
Default Re: Aggrevating Variation in Block Size

Why are you people shying away from laying the block with mortar? You are going to lay the most difficult part of the build with fireclay. Laying the base with mortar would get builders used to handling the tools of the trade.
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  #8  
Old 06-04-2014, 07:53 PM
Peasant
 
Join Date: Mar 2014
Location: USA
Posts: 48
Default Re: Aggrevating Variation in Block Size

Quote:
Originally Posted by Campmaki View Post
Why are you people shying away from laying the block with mortar? You are going to lay the most difficult part of the build with fireclay. Laying the base with mortar would get builders used to handling the tools of the trade.
Maybe because the plans recommend dry stacking and filling every other core with re-bar and concrete?
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  #9  
Old 06-04-2014, 07:55 PM
Peasant
 
Join Date: Mar 2014
Location: USA
Posts: 48
Default Re: Aggrevating Variation in Block Size

And because my height works out better without the mortar joints...
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  #10  
Old 06-04-2014, 08:26 PM
Master Builder
 
Join Date: May 2011
Location: South Australia
Posts: 548
Default Re: Aggrevating Variation in Block Size

I realise it'll be a PITA, but can you sort them before you start, so each course contains blocks of roughly the same height?
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