Ground Beams and pouring a new slab next to an existing one.

   / Ground Beams and pouring a new slab next to an existing one. #1  

Bearsixty7

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Ok, Educate me on ground beams and pouring a slab next to an existing one. I have poured a few free standing slabs over the years and understand compacting the ground, constructing forms, use of rebar and chairs, etc.

Now I am wanting to pour a 8.5' wide x 40' long 5" thick slab beside my existing concrete floored shop. I will eventually add a frame and roof only to match the existing roof in regards to material and pitch.
This slab (carport if you will) will just be housing the tractor and all the implements, etc. so nothing real heavy.

What I can't find is how to calculate how wide and deep the ground beam needs to be.

I believe since the roof supports will just be at the outer edge, that is the only place I need a ground beam, correct?

Also, what is the best way to handle the gap between the old slab and the new one?
I planned to drill into the old slab 4 inches and glue in some of the ends of the rebar with AnchorFix-1 Anchoring Adhesive. With the new slab being 5" thick I planned to drill the holes 2-1/2" down from the top of the old slab to be centered in the new concrete. I was going to also attach a 1x4 vertically along that joint, notching out around the rebar to act as an expansion and control joint. Will that work or what is the better method?
 
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   / Ground Beams and pouring a new slab next to an existing one. #2  
Do one or the other, not both.
Pinning the new to the old is good, using expansion joint [foam or fiber] is good.
But not at the same time.
 
   / Ground Beams and pouring a new slab next to an existing one. #3  
When I did this once I just pinned it to the existing slab and poured right against it. Worked out fine.
 
   / Ground Beams and pouring a new slab next to an existing one. #4  
Same. Pounded some 12" rebar into the slab and poured.
 
   / Ground Beams and pouring a new slab next to an existing one. #5  
Ok, Educate me on ground beams and pouring a slab next to an existing one. I have poured a few free standing slabs over the years and understand compacting the ground, constructing forms, use of rebar and chairs, etc.

Now I am wanting to pour a 8.5' wide x 40' long 5" thick slab beside my existing concrete floored shop. I will eventually add a frame and roof only to match the existing roof in regards to material and pitch.
This slab (carport if you will) will just be housing the tractor and all the implements, etc. so nothing real heavy.

What I can't find is how to calculate how wide and deep the ground beam needs to be.

I believe since the roof supports will just be at the outer edge, that is the only place I need a ground beam, correct?

Also, what is the best way to handle the gap between the old slab and the new one?
I planned to drill into the old slab 4 inches and glue in some of the ends of the rebar with AnchorFix-1 Anchoring Adhesive. With the new slab being 5" thick I planned to drill the holes 2-1/2" down from the top of the old slab to be centered in the new concrete. I was going to also attach a 1x4 vertically along that joint, notching out around the rebar to act as an expansion and control joint. Will that work or what is the better method?
Speaking of getting advice worth what you pay for it. Don't you think it would be wise telling the folks you have the most expansive soil to be found in Texas? It's like daylight and dark pouring concrete where you are located compared to 50 miles East or West,not to mention Iowa,Indiana and Michigan where all your carfully thought out advice is coming from.
 
   / Ground Beams and pouring a new slab next to an existing one. #6  
not to mention Iowa,Indiana and Michigan where all your carfully thought out advice is coming from.
Well, I was in Wisconsin when I did that pour, so... :p
 
   / Ground Beams and pouring a new slab next to an existing one.
  • Thread Starter
#7  
What about ground beam
Speaking of getting advice worth what you pay for it. Don't you think it would be wise telling the folks you have the most expansive soil to be found in Texas? It's like daylight and dark pouring concrete where you are located compared to 50 miles East or West,not to mention Iowa,Indiana and Michigan where all your carfully thought out advice is coming from.
I have that part covered with excavating and compacting better aggregate. I have seen a few slabs poured around here that have been pretty stable for 15+ years. What I don't know is how to determine width and depth for the ground beam.
From all my researching, it almost seems the only thing that matters is that it goes below the frost line.
I contacted our town secretary and he responded he forwarded my the info to the building official. Hopefully he will respond in a day or two.
 
   / Ground Beams and pouring a new slab next to an existing one. #8  
What about ground beam

I have that part covered with excavating and compacting better aggregate. I have seen a few slabs poured around here that have been pretty stable for 15+ years. What I don't know is how to determine width and depth for the ground beam.
From all my researching, it almost seems the only thing that matters is that it goes below the frost line.
I contacted our town secretary and he responded he forwarded my the info to the building official. Hopefully he will respond in a day or two.


Hmm, Below the frost line? Yes, good advice, But even here in New England, Alaskan slabs are popular and work just fine. I have two under shed roof additions to the house. One is the kitchen /dining room. If there were troubles. I would hear about it from my wife! ;-)

Dry soil can not heave.
 
   / Ground Beams and pouring a new slab next to an existing one. #9  
Depth of frost line in Collin County is only a few inches so that's not a concern. The single most enemy is fluxiating moisture. Your dirt shrinks when dry (the reason you see large cracks in summer) and expand's when wet. You want ground to gently slope away from slab and not pond less than 8 feet from slab. This is 10 fold important where roof dump's water next to slab. You can gutter or not but if you gutter it's a good idea to pipe rainwater away from building so that a few square feet isn't saturated where downspout dumps. Again,control extreme and sudden fluxuation in groud moisture.
I would put a 10 to 12 inch wide X 14 or more inches deep on all 4 sides,2 to 4 inches sand (no stone) in bottom. Since you don't have to worry about drywall cracks or binding doors,I wouldn't dowl old and new togeather so old and new slab can move independently. 8.5 x 40 is almost certain to crack. How much is to be seen. If you want to try and prevent cracks,3 8" to 10" piers 10 feet apart down center 18" deep w/4" sand will add alot of stability. Deeper, wider and additional beams and piers never hurt if you can afford them.
I have mixed feelings about saw cuts and expansion joints. Sidewalks definatly but I recently poured a 30x40 storage for myself and did no joints other than walk and driveway approachs. Most often rule broken by contractors is no more than 6" slump. No reputable plant will send soup out but labors commonly add water on site if you don't forbid them.
 
   / Ground Beams and pouring a new slab next to an existing one. #10  
Not familiar with TX soils. But why not pour your 8.5’x40’ in sections. In SEMO, we get lots of ground movement (New Madrid fault line) so large pours almost always crack soon. Smaller pours can help to control cracks especially as you have joints where movement can occur.
My suggestion is to do do 2 pours of 2- 8.x10. Pour one skip one after these set, pull inside forms, put foam where joints will be and pour the 2nd set.
 
 
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