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Discussion Starter #1
I'm currently underpinning my house and I'm looking for a little guidance. I will be doing three foot sections six ft apart leaving 3-4 inches of space at the top to pack non shrink grout. A few questions to start, how dry do I make the non shrink? Is 3-4 inches too thick? Should I point it in or just use a hawk and slick?
 

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Renaissance Man
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Make it dry and pack it in with a short 2x4 and hammer, etc. Your plan sounds good in terms of excavation,...I assumed you consulted an engineer and permitted the job?

A good grout mix is 1:1 concrete sand/Portland up to about a 3:1. You can add 1/2 stone to really give it body if your pack is thick, 3-4 inches.

You can also forget the dry pack and just over form on the inside and vibrate the forms - much quicker and better in my opinion.
 

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Discussion Starter #3
superseal said:
Make it dry and pack it in with a short 2x4 and hammer, etc. Your plan sounds good in terms of excavation,...I assumed you consulted an engineer and permitted the job? A good grout mix is 1:1 concrete sand/Portland up to about a 3:1. You can add 1/2 stone to really give it body if your pack is thick, 3-4 inches. You can also forget the dry pack and just over form on the inside and vibrate the forms - much quicker and better in my opinion.
Thanks for your response. By over form you mean extend the forms up to above the current footing and pour essentially the entire pin, Should I be worried about shrinkage? As it stands I have done one pin and I let it cure for 3 days before I used the non shrink. I thought about pouring the entire thing as well.
 

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Discussion Starter #4
Also. I have three brick pillars holding up the main beam of the house and would like to replace them with steel ones.

What size footing should I use?
 

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First off, what are you catching? Is this a framed house, or one of masonry..........if you're pinning to a wood sill plate, dry pack, or any grout is not your answer.........first, let's find out what your house is made of.......?
 

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Renaissance Man
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I doubt he's dealing with a wood sill plate under a footing, probably just trying to lower the floor level by the sounds of it,...hence the brick pier footing size question.

Obviously we now know he hasn't consulted an engineer, nor is this a permitted job. I won't slam him on it, but he should know better being a "young mason" not to fool with structure without another set of eyes.
 

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Thanks for the response. My house is a double brick walled house sitting on a field stone foundation, built in 1909 with a lime mortar. I am tackling this project conservatively and responsibly. I have had engineers in that specialize in this type of work. The two engineers that I have consulted with had two different opinions which raised alarms on my end and that's why I'm on this forum asking for opinions. I will post pics soon, thanks again for your responses!
 

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What's the cause of the subsidence? Leaking drains, trees on shrinkable clay, built on landfill site, or over mine shaft? etc
 

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Thanks for the response. My house is a double brick walled house sitting on a field stone foundation, built in 1909 with a lime mortar. I am tackling this project conservatively and responsibly. I have had engineers in that specialize in this type of work. The two engineers that I have consulted with had two different opinions which raised alarms on my end and that's why I'm on this forum asking for opinions. I will post pics soon, thanks again for your responses!
There is an old saying, if you can't make up your mind between the 2 girls you want to date, screw the two and find a 3d one. Same with your Engineers, get the 3d opinion and see what he will say.

When underpinning foundations, the most important factor is the load calculation which need to be supported, soil condition, and proper connection between the old footing and new. If you had two different opinion and 2 different ways of doing this, and it will work, then there is nothing wrong with it. Get a 3d opinion if you not sure.
You not gonna find any answers here, because it is a structural issue and nobody here has no clue what the condition of your structure is and what you dealing there with.
 

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Using 4" of non shrink grout will not hurt anything.

I will typically set the footing height so that I can slide a 2X4 into the gap, this uses less grout, which saves time and money.
 

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Discussion Starter #14
tgeb said:
Using 4" of non shrink grout will not hurt anything.

I will typically set the footing height so that I can slide a 2X4 into the gap, this uses less grout, which saves time and money.
Thanks for your reply!

A 2x4 on its side i.e. 1.5 inch high? Or the other way?
 

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Honestly don't know why you would use wood there......the compressive strength between grout and even a treated 2x are not even close....if you're just looking for filler, why not soaps or bricks?

I personally would try to use far less.....maybe 1/2-1".....but maybe the manufacturer of the grout could tell you what they recommend......
 

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rockmonster, I think tgeb is using the 2x4 just to pound the shrinkproof in I don't think he means to leave the 2x4 in there. I usually use shrinkproof grout at 3/4 to an inch and for this job I'd probably fill with a grout bag and compress with a 3/4" slicker. But any way that works and gets it in tight to the top is good I think. :)

Nice job youngmason. I guess superseal is correct, trying to get a bit more head room down there?
Dave
 

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You got it Dave! Thanks!! More head room it is, I will be building a basement apartment once the head room is a decent height. Ok I will try and make the area 1 inch and pack it with non shrink after that, I guess I could use a birds mouth to help get the concrete that tight.

Does anyone have advice on what type of steel post to use as a replacement for what is currently three brick pillars holding up the main beam.
 

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If you mean to replace 3 piers with 1 lally column, you're gonna need an engineer to help you......it's what that lally is supporting that will determine if you can go from 3 to 1. An I beam or LVLs are probably what you'll need.......they'll also help you with determining the size of the footing as well, here they're usually 30"x30"x12", but soil conditions and loading will determine sizing.....

Lally columns come in 3 1/2 or 4" diameter generally, filled with LW concrete.....16 ga I think........there's also a world of choices with round or square hollow steel posts as well, but the lally has been the one for many years.....project looks good! Lotta fun.......
 

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Standard retrofit columns I spec on jobs like this are 1/4"x 4" round concrete filled. Weld 8"x 8" by 1/4" plates to top and bottom. My footing sizes are mostly 2 x 2 but some can be larger depending on point loads.

You really should run numbers in terms of soil bearing and load distribution because nobody here can give you finite advice without seeing the whole scope.
 
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