Block Foundation Addition

 
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Old 03-11-2010, 06:54 AM   #1
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Block Foundation Addition


ok i adimt, i know almost nothing about block wall foundations.


a homeowner contacted me to build an addition. they have a block foundation and would like the addition to be the same.

i contacted a local mason and he said that he would just butt his block up to the old ones and mortar them in.

i asked him if the new joint between old and new would leak....he said no.


is this the way u would do the job? or would you remove the old block and tie into the old foundation?


i am just worried about that joint not being water tight

thanks for the help
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Old 03-11-2010, 07:17 AM   #2
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Re: Block Foundation Addition


So you would suggest making the existing foundation weaker to accept the new addition. How long have you been doing this?

I do 10-20 additions a year, I have never cut into the existing yet, but there is always that exception out there waiting.

Properly slope the grade away from the wall, provide drainage at the footer level and finally use a water proofing material on the block. Your good to go. If it is a basement then you might look into some of the more detailed waterproofing systems.

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Old 03-11-2010, 07:20 AM   #3
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Re: Block Foundation Addition


I think he's referring to the intersection of old to new. The inside corner is notorious for leaking.
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Old 03-11-2010, 04:34 PM   #4
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Re: Block Foundation Addition


why would it matter how long/many i have done?

im not a mason. so i ask for help.
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Old 03-11-2010, 04:36 PM   #5
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Re: Block Foundation Addition


I would score a little notch down the joint and fill with a good brand non-hardening caulk
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Old 03-11-2010, 05:01 PM   #6
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Re: Block Foundation Addition


It's a good question
C'mon all you masons....chime in and share how you do it.
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Old 03-11-2010, 05:25 PM   #7
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Re: Block Foundation Addition


Quote:
Originally Posted by kubie View Post
ok i adimt, i know almost nothing about block wall foundations.


a homeowner contacted me to build an addition. they have a block foundation and would like the addition to be the same.

i contacted a local mason and he said that he would just butt his block up to the old ones and mortar them in.

i asked him if the new joint between old and new would leak....he said no.


is this the way u would do the job? or would you remove the old block and tie into the old foundation?


i am just worried about that joint not being water tight

thanks for the help
Just butt and butter. If you are worried about moisture issues you need other solutions such as draintile/membrane etc. Masonry no matter how it is tied into the existing foundation is problematic from a moisture standpoint. my .01!
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Old 03-11-2010, 06:44 PM   #8
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Re: Block Foundation Addition


The joint will most likely crack, but that is usually how it is done. I would nail some wall ties into the existing and rake back the joint and caulk it. If there is a moisture issue you will need to address that no matter how you lay the block.
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Old 03-11-2010, 08:58 PM   #9
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Re: Block Foundation Addition


Where are you located in WI? I'd be more than happy to give you a price!
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Old 03-11-2010, 09:38 PM   #10
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Re: Block Foundation Addition


This is how I do it. If the cell where you are connecting is grouted solid, drill and epoxy rebar pins, I do the footing and a couple/few in the wall, maybe two in a crawl, maybe 4 in a full basement. I usually put a bend in the bar and go into the second cell in the new wall. Grout accordingly. If the cell is ungrouted, I will open it up, usually slot it about 4" wide, and insert rebar connecting new to old. I use what we call z bars, 2 90's in opposite directions. Waterproof is usually thoroseal brushed with tar, or I get it sprayed with (trade name escapes me) some hot bituminous stuff. Also may use FSB by silpro followed by concrete finish for a nice look and a good measure of protection. This is fairly bulletproof. At the joint, you can rake it and caulk with any number of great products, but I've found no need with my method, as I've never seen one open up. I am curious as to how others do this as well, but this method has worked for me....
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Old 03-11-2010, 09:49 PM   #11
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Re: Block Foundation Addition


The waterproofing should be outside the CMU envelope, and should be designed to allow for movement between the existing and the new.
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Old 03-13-2010, 08:46 PM   #12
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Re: Block Foundation Addition


The new block just gets mortared into the old block.
Attached Thumbnails
block foundation addition-slide1.jpg   block foundation addition-slide2.jpg   block foundation addition-slide3.jpg  
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Old 03-13-2010, 08:49 PM   #13
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Re: Block Foundation Addition


One last pic.
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Old 03-14-2010, 12:05 AM   #14
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Re: Block Foundation Addition


to many varibles to be considered here...as Rockmaster said.. drill rebar and epoxy is a good start but then again more varibles...wall being drilled solid or block ?....has block been filled with concrete ect?...proffesional footing or will it settle and pull wall away or fail somewhere else causeing leaks ect ect
..most fasteners make me nervous around empty cores as l know how easly a block can fail given the wrong stress;s....what realy makes me nervous is folks on my chevy truck forum that use blocks for jackstands,,,


ps..good pics above


Last edited by CanCritter; 03-14-2010 at 12:09 AM.
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