# block foundation addition



## kubie (Oct 19, 2008)

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:shutup:

thanks for the help:thumbup:


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## dakzaag (Jan 6, 2009)

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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## tcleve4911 (Mar 26, 2006)

I think he's referring to the intersection of old to new. The inside corner is notorious for leaking.


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## kubie (Oct 19, 2008)

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

im not a mason. so i ask for help.


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## GoToBrick (Nov 7, 2009)

I would score a little notch down the joint and fill with a good brand non-hardening caulk


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## tcleve4911 (Mar 26, 2006)

It's a good question
C'mon all you masons....chime in and share how you do it.:sad:


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## lukachuki (Feb 11, 2005)

kubie said:


> 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.
> ...


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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## NJ Brickie (Jan 31, 2009)

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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## 6stringmason (May 20, 2005)

Where are you located in WI? I'd be more than happy to give you a price!


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## Rockmonster (Nov 15, 2007)

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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## Tscarborough (Feb 25, 2006)

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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## IanS (Sep 18, 2009)

*I am no mason but...*

The new block just gets mortared into the old block.


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## IanS (Sep 18, 2009)

*final*

One last pic.


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## CanCritter (Feb 9, 2010)

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


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