# How deep should I dig for 20"Hx7"W concrete wall?



## almazon (Feb 19, 2012)

Heya guys,

Title says it all...

How deep should I dig to make footing for 20"H x 7"W Poured Concrete Wall?

Thank you in advance,
almazon


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## joecaption (Nov 30, 2011)

Below whatever your frost level is.


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## almazon (Feb 19, 2012)

Just wonder what that would be?


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## danpik (Sep 11, 2011)

http://soundfootings.com/pdf/US_Map_Frost_DepthAVG.pdf


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## Live_Oak (Aug 22, 2013)

Looks like 48" would do it in upstate NY. If this is on a hill, or has a lot of moisture, you want to go deeper.


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## 747 (Feb 11, 2005)

If i'm not mistaken here in Illinois (frostline) would be at least four feet. So i would go 4.5 to be safe.


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## PoleCat (Sep 2, 2009)

The local building department has the correct answer.


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## oh'mike (Sep 18, 2009)

That is a heck of a footing for a 20 inch tall wall----exactly what is this being used for?


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## almazon (Feb 19, 2012)

oh'mike said:


> That is a heck of a footing for a 20 inch tall wall----exactly what is this being used for?


Thanks oh'mike for understanding my concern!

After leveling out my Front Yard with pavers my Fence still on slope:









So for this reason I decided to dig the Fence out, slightly move it away from sidewalk and place it on top (or inside) Poured Concrete Wall:









or:




























So the question is how deep should I go for this 20 inch high and 7 Inch Wide wall?










Thanks again,
almazon


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## Live_Oak (Aug 22, 2013)

That's going to need a lot of shear strength, as well as for the wall itself to withstand the hydrostatic pressure of the water wanting to move downhill. You need to talk to your local building department about the project. You've definitely got to be BELOW frost depth though. 48" might not be enough though for the footing, and you've got to be sure to have the proper drainage around the wall as well. This isn't a "simple" project.


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## concretemasonry (Oct 10, 2006)

Going down to the "frost depth" is really a strange concept for a landscaping application. The "frost depth" is for buildings/structures and is based on a 50 to 100 year period where may be enough heaving of frost susceptible soil to cause structural damage to a building in that long period. Many soils are not frost susceptible and will not heave.

Has anyone ever seen a highway built on a foundation below the frost depth? The simple answer is that some structures can tolerate movement and a 5' frost heave on a road can be tolerated because the thing that is important is the DIFFERENTIAL movement, so if a landscaping wall heaves upward, it moves just about as much as the remaining soil. - Technically, very slightly more, but it just needs the strength to hold together. Soil freezes from the top down.

In the photos shown, the wall is only needed for the small lateral loads and a spread footing under the wall could create problems. The entire area inside the fence is composed of interlocking concrete pavers that are not designed with regard to the "frost depth" because they move together and should never be connected to any rigid structure.

Even the common dry stacked segmental retaining walls (SRWs) are but with no concrete footing allowed and no concrete or mortar in the wall - Just 8" buried for a 4' non-engineered wall, because of the lateral shear resistance.

Why the 7" wall thickness? - Is that the width of the shovel?

Dick


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## oh'mike (Sep 18, 2009)

I thought that might be a landscape feature---I'm not a concrete guy---but we typically dug a shallow trench--about 10" or so--and set the forms---a couple of lengths of light rebar might be added to keep the wall intact if if ever cracks---


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## brockmiera (Oct 9, 2012)

I agree with concrete. No reason to go below frost for this. Good rule of thumb is go as below grade as much as you are above. Frost will cause the ground to heave but this wall will be allowed to float. much like a monolithic slab will. I can't imagine the hydrostatic pressure will be enough to cause any issues unless there is a flood. In that case I'm sure your wall will be the least of your worries. 

If it were me, I would dig down 20" + 8" . the 20" will be 7" wide but the 8" below that will be 14" wide to create load distribution into the soil. I'd also run two runs of #4 rebar in the footer.

Disclaimer: If this wall will be retaining earth on your side of the fence line there will need to be drainage issues taken into consideration. Please let us know if that is the case.


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## DexterII (Jul 14, 2010)

Unless there is more to it than leveling the top of the fence, and given the possibility of undermining a municipal sidewalk, I would focus on the fence itself. If you are satisfied with the height at its' lowest point, which looks like only a couple inches of difference, and assuming that the posts are stable, it could be as easy as running a line along the top, cutting the tops of the high ones, loosening a few bolts, dropping it down level, and you'd be good to go. As mentioned, you would have to check with your local autorities, but I would guess that you could not install it as is atop a 20" high concrete wall, so would end up with an awful lot of cutting to shorten the whole thing. If you still wanted to break the fence up from the inside, visually speaking, you could lay however many rows of landscape blocks on nothing much more than a shallow bed of compacted gravel, just like you have for your pavers. Dick actually knows what he's talking about, so maybe this doesn't make sense, but it's my 2 cents worth.


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## Live_Oak (Aug 22, 2013)

"So for this reason I decided to dig the Fence out, slightly move it away from sidewalk and place it on top (or inside) Poured Concrete Wall"

Guys, the fence will be "inside" the concrete wall, meaning that it's what's anchoring that fence. With no mention of fence posts going below frost line. With the fence merely anchored in a shallow not below frost line concrete "wall", it's going to need to be able to stand up to a winter wind pushing on it's ice filled privacy mesh. And that's why I said that the entire structure should go below frost level.


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## brockmiera (Oct 9, 2012)

Live_Oak said:


> "So for this reason I decided to dig the Fence out, slightly move it away from sidewalk and place it on top (or inside) Poured Concrete Wall"
> 
> Guys, the fence will be "inside" the concrete wall, meaning that it's what's anchoring that fence. With no mention of fence posts going below frost line. With the fence merely anchored in a shallow not below frost line concrete "wall", it's going to need to be able to stand up to a winter wind pushing on it's ice filled privacy mesh. And that's why I said that the entire structure should go below frost level.


I've never seen fence posts be required to go below frost. Again they are allowed to float. Whether he places them inside or anchors them to the top it should be fine.


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## almazon (Feb 19, 2012)

Thanks guys for ALL of your responses!

At this time all I can say is I am not planning to go below frost line.
I will continue digging this weekend. Probably up to 18".

Of course there will be rebars and draining involved. I got very nice Black & Decker books...

I already called one of our local Ready Mix company. They gonna charge me APPROX $198 per sq yard of PS4000 (or whatever), if its gonna be just 1 yard. More yards cheaper.

I calculated 1 yard is what I need for this side. Most likely I will need another sq yard for another side.

That's all I can say for now. I will keep you posted!

Thanks again,
almazon


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## almazon (Feb 19, 2012)

Hello guys,

Remember me? Here's an update:

1. Wall is going to be 8". Not 7" as previously planned.

2. After leveling everything out starting from the lowest point of the wall on other side (9") I ended up with 29" at highest point of the wall. Not 20".










3. I dug for at least as same as height of the wall. 
4. I banged Vertical rebars approx. 4-6" into the ground, 2" from the top of the wall and 16" from each other. 
5. I also installed Horizontal rebars 8" from each other.










6. I finished building both Outer and Inner walls of the Form (shown covered temporarily with corrugated plastic)



















7. On the bottom these walls are holding to each other with 1/2" x 12" Stainless Steel rods installed 4' from the bottom and 3' apart.










8. Each of these rods go through 1.25" x 8" PVC pipe that will stay there after concrete will be poured AND served as part of drainage.




















Now, I am working on Stakes, Diagonal and Horizontal Bracing.

I have 2 questions:

1. What would you recommend to use to hold Form Sides together?
2. Will 16 gage wire loops do the trick?
3. Or should I go with the rods?

Also:

4. If the form will be secured on one side can I skip securing it on another side?

Thank you in advance,
almazon


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## stadry (Jun 20, 2009)

missed this thread,,, we work'd on the richmond off the outerbridge so, if i recall correctly, you don't get any appreciable frost in staten is - same as e nj, maybe 6" at the most,,, btw, what an amazing formwork for a diy'er :thumbsup: 

you ask'd 4 ?'s, not 2 :jester: i'd wire the forms w/tie wire - 24" spacing on the top row & 12" on the btm - drill a 1/8" hole, run wire thru, & secure to nail on the exterior - EACH side !

good luck !


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## Canarywood1 (May 5, 2012)

I agree with IRC about more ties on the lower part of the wall,but the upper part just nail some 2x4 across the top of the forms,save you from a lot of drilling.


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## stadry (Jun 20, 2009)

Lord knows he's used to 2 x 4's by now,,, good catch, woody :thumbsup:


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## almazon (Feb 19, 2012)

itsreallyconc said:


> missed this thread,,, we work'd on the richmond off the outerbridge so, if i recall correctly, you don't get any appreciable frost in staten is - same as e nj, maybe 6" at the most,,, btw, what an amazing formwork for a diy'er :thumbsup:
> 
> you ask'd 4 ?'s, not 2 :jester: i'd wire the forms w/tie wire - 24" spacing on the top row & 12" on the btm - drill a 1/8" hole, run wire thru, & secure to nail on the exterior - EACH side !
> 
> good luck !


Thanks IRC,

I am planning to do a PLENTY of wiring at both TOP and BOTTOM at 16" spacing.


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## almazon (Feb 19, 2012)

Canarywood1 said:


> I agree with IRC about more ties on the lower part of the wall,but the upper part just nail some 2x4 across the top of the forms,save you from a lot of drilling.


Thanks Canarywood1,

I don't mind drilling!


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## Canarywood1 (May 5, 2012)

almazon said:


> Thanks Canarywood1,
> 
> I don't mind drilling!


Your call!


Don't forget to use a release agent on the interior of the forms.


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## almazon (Feb 19, 2012)

Canarywood1 said:


> Your call!
> 
> 
> Don't forget to use a release agent on the interior of the forms.


Now, that's interesting, since book suggesting Vegetable Oil.

What would you recommend?


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## stadry (Jun 20, 2009)

get a couple gallons of diesel & an old broom,,, if you use vegetable oil, it might attract rodents from the fresh kill :laughing: btw, not even sure diesel's legal anymore but you are in staten island :whistling2:


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## Canarywood1 (May 5, 2012)

As IRC said #2 diesel would be my choice,has more wax in it than #1.


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## almazon (Feb 19, 2012)

Another issue with my project is that Winter is here. As of right now whole form is covered with 4 mil plastic. Of course I will look into mild days to finish wiring and securing the form, but...

How long do you think I will have?


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## stadry (Jun 20, 2009)

' How long do you think I will have? ' to what,,, finish it ? have any chance of finding conc blankets ? you can rent them from gamka in edison but you might also find 'em on s.i.,,, w/blankets, i'd pour lo-slump conc in the am on a 40f & rising day when nite temp won't drop below 30f & cover w/conc blankets for a wk - unfortunately, this is all based on weather in my head  making off the previous ' iffy ',,, some pours we'd call 4 conc the next am & cancel when arriving @ 0-dark-30 :huh: that's conc ' life ' - best !


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## almazon (Feb 19, 2012)

itsreallyconc said:


> ' How long do you think I will have? ' to what,,, finish it ? have any chance of finding conc blankets ? you can rent them from gamka in edison but you might also find 'em on s.i.,,, w/blankets, i'd pour lo-slump conc in the am on a 40f & rising day when nite temp won't drop below 30f & cover w/conc blankets for a wk - unfortunately, this is all based on weather in my head  making off the previous ' iffy ',,, some pours we'd call 4 conc the next am & cancel when arriving @ 0-dark-30 :huh: that's conc ' life ' - best !


 Thanks irc,

What I really meant to ask is *how long do you think I will have* for the form to withstand this weather before the pour?


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## stadry (Jun 20, 2009)

if you've covered it, you're fine,,, you'll easily see the plastic rip/tear/degrade,,, if/when it does, recover it til you can get poured :thumbsup:


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## almazon (Feb 19, 2012)

itsreallyconc said:


> if you've covered it, you're fine,,, you'll easily see the plastic rip/tear/degrade,,, if/when it does, recover it til you can get poured :thumbsup:


Thanks again irc,

That's what I wanted to hear...


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## almazon (Feb 19, 2012)

Today in the morning guy from Building Dept knocked on my door...:whistling2:

He said that there was a Complaint, BUT he did not find anything illegal. He also said that I can continue to do what I am doing as long as fence gonna be no higher than 6 feet.


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## beenthere (Oct 11, 2008)

almazon said:


> Today in the morning guy from Building Dept knocked on my door...:whistling2:
> 
> He said that there was a Complaint, BUT he did not find anything illegal. He also said that I can continue to do what I am doing as long as fence gonna be no higher than 6 feet.


LOL, jealous neighbor.


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## almazon (Feb 19, 2012)

Hey guys,

Spring is finally here. So is my project.
Looks like I am at the finish line with it.



itsreallyconc said:


> get a couple gallons of diesel & an old broom,,, if you use vegetable oil, it might attract rodents from the fresh kill :laughing: btw, not even sure diesel's legal anymore but you are in staten island :whistling2:


I came with Diesel. It took 1 gallon to cover whole form inside.

Now I have couple of questions...

1. Will one layer be enough?
2. Is it necessary to apply it RIGHT BEFORE the pour or one time is enough for like lifetime?

TIA
almazon


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## stadry (Jun 20, 2009)

we sprayed it on forms right before placing


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## almazon (Feb 19, 2012)

itsreallyconc said:


> we sprayed it on forms right before placing


Thanks itsreallyconc!

Otherwise it will stick?


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## stadry (Jun 20, 2009)

prevents the conc from sticking to the forms & making form removal a LARGE pita,,, helps prevent pulling off unconsolidated conc, too, there lowering finishing costs :thumbup:

richmond hgwy still rideable ? 1 of my 1st jobs in ny metro area


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## almazon (Feb 19, 2012)

itsreallyconc said:


> prevents the conc from sticking to the forms & making form removal a LARGE pita,,, helps prevent pulling off unconsolidated conc, too, there lowering finishing costs :thumbup:
> 
> richmond hgwy still rideable ? 1 of my 1st jobs in ny metro area


You mean Staten Island Expressway, or 278? Yes, but its a LOT of construction going on causing bumper-to-bumper everyday. Both ways. Some of these changes are very nice while others are completely useless.

So, back to my form...

You advise to do it right before the pour otherwise its gonna cause problems? Even if I did it before? How long before the pour?


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## almazon (Feb 19, 2012)

Okay, guys!

This is where I am standing with my project.
There are 2 sides of the wall since I live on the corner.

1st side:

As you remember I covered with Plastic for the Winter. I still covering it after finishing work in case of Rain:























































And 2nd side:





































As for EXTRA strength I am going to screw 1x2 across the top of the forms every like 2-3 feet.

Will this work without supporting exterior (sidewalk) side of the form?

TIA,
almazon


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## stadry (Jun 20, 2009)

it would work even if you were rebuilding the outerbridge wing walls

:laughing:


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## almazon (Feb 19, 2012)

itsreallyconc said:


> it would work even if you were rebuilding the outerbridge wing walls
> 
> :laughing:


No, man, I am serious!
Do I have a chance?


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## jomama45 (Nov 13, 2008)

From what I can see, the wire ties you have in place are more than enough to keep the forms from spreading, which is the biggest concern. The props on the inside (yardside) are only keeping it from falling over while it's wet. I don't think you have anything to worry about.........


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## Msradell (Sep 1, 2011)

Pour it already!


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## almazon (Feb 19, 2012)

Heya guys,

Truck will be coming this Wednesday at noon.

I calculated 4.5 cubic yards. They quoted me $715.
I will give it one more coat of diesel and probably add few more wires.

It looks like concrete guys are expecting to see a whole crew here.
That makes me worry. I told them I will be the only one.
Is that a problem? Will I be able to handle it myself?

Do I have to use a concrete vibrator?

TIA
almazon


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## Msradell (Sep 1, 2011)

almazon said:


> It looks like concrete guys are expecting to see a whole crew here.
> That makes me worry. I told them I will be the only one.
> Is that a problem? Will I be able to handle it myself?


Either they are you are going to be in for a big surprise, hopefully it will be them!


> Do I have to use a concrete vibrator?


You don't have to have one but it would certainly make the concrete flow smoother into the form and reduce the possibility of voids. It will also probably give you a better finish of the concrete against the forms.


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## jomama45 (Nov 13, 2008)

Sooooo, how did it go?????


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## almazon (Feb 19, 2012)

jomama45 said:


> Sooooo, how did it go?????


LOL! It went great! IMAO!

Ok guys,
This is what I got!

I calculated 4.53 cubic yards and ordered slightly more (5 cubic yards). When the truck finished pour I ended up slightly short and had to rent a Mixer and buy another 16 bags (5000) from local Home Depot.

After all form stood well on both LOWER...


















...and HIGHER sides


















The only issue is that, because I was working alone (well not exactly - my wife helped me) I missed couple of spots and did not finished it properly on top.

For this purpose I got Hydraulic Water-Stop Cement by Quikrete AND need your input on this:









Another question is when I can start removing wood?


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## almazon (Feb 19, 2012)

Guys,

Still, can I start removing the wood?

My sixth sense telling me YES, but I just wanna make sure...


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## jomama45 (Nov 13, 2008)

almazon said:


> Guys,
> 
> Still, can I start removing the wood?
> 
> My sixth sense telling me YES, but I just wanna make sure...


Definitely safe to strip it now.......


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## almazon (Feb 19, 2012)

Ok, guys,

My agenda slightly changed since I am NOT planning to put Chain Link Fence on top of this Concrete Wall that I just poured. Instead I want to go with Concrete Block Wall. Thanks to the guy from Building Dept who gave me this idea. Then most likely I am going to finish it with Stucco or something.

When I poured concrete I did not really finish it on top and its NOT really leveled. So now I want to finish it with Hydraulic Water-Stop Cement (Quikrete) to make it more leveled before laying out Blocks.

That's why I did not remove the wood yet...

Is this stuff Ok to do it?
Do I have to prepare (finish, level, etc) it this way?
Or I will be Ok starting with Blocks just like that?
Just make sure that first row gonna be leveled?

Thank you in advance,
almazon


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## Msradell (Sep 1, 2011)

If you are going to just put block on top of it there's no need and leveling at 1st. You can just pulling string line for the top of the 1st course and level the blocks with the mortar bed. If fewer types of material that are involved the better.


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## jomama45 (Nov 13, 2008)

You're changing the entire scope of the project now. Before, it was a light fence, now it's a block wall it's supporting? Now, with the change, and your environment, as well as it's location next to a sidewalk, I'd highly suggest you don't build a block wall on top of that with out frost protection...........:no:


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## almazon (Feb 19, 2012)

Anyway, guys,

I removed the wood and this is what I got so far. I think its not THAT bad:


















I decided to keep existing Chain Link gates for now: 



























Need some finish in couple corners:


















I think it will be enough support for Block Wall considering it goes in average 3' deep.
I am planning to use 6" Blocks (Wall itself is 8") and flush it with Inner wall giving some space for finishing on Outside. 



Msradell said:


> If you are going to just put block on top of it there's no need and leveling at 1st. You can just pulling string line for the top of the 1st course and level the blocks with the mortar bed. If fewer types of material that are involved the better.


This is what I am talking about when I say its not really leveled:









Do you think I will be able to fix (bring to level) it at 1st course of Blocks with the Mortar Bed?

Thank you in advance,
almazon


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## Msradell (Sep 1, 2011)

That should be very simple to correct on the 1st course of block!


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## almazon (Feb 19, 2012)

Hey guys,

Thanks a lot all for helping me with this project!
I don't think it would be possible to do it without your helpful advices! :thumbsup:

Its time for my next Laying Out Concrete Block Wall project! 

Thanks again,
almazon


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## jomama45 (Nov 13, 2008)

almazon said:


> I think it will be enough support for Block Wall considering it goes in average 3' deep.
> I am planning to use 6" Blocks (Wall itself is 8") and flush it with Inner wall giving some space for finishing on Outside.


I realize you've likely already made your mind up, and there's no way to change it, but I still think this is a bad idea. Sure, you have a few feet of wall in the ground, but is it set on a spread footing, meaning a footing that's about 8" thick and twice the width of the wall? Is the below grade portion of the wall formed smooth on both sides to deter frost "picking" against the wall? Is the wall isolated from the flatwork surrounding it with proper material? Unfortunately, I believe the answer to every one of these questions is "NO", and what you're trying to do goes against all "best practices" in the construction of a foundation and wall in a frost zone............


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## almazon (Feb 19, 2012)

jomama45 said:


> I realize you've likely already made your mind up, and there's no way to change it, but I still think this is a bad idea. Sure, you have a few feet of wall in the ground, but is it set on a spread footing, meaning a footing that's about 8" thick and twice the width of the wall? Is the below grade portion of the wall formed smooth on both sides to deter frost "picking" against the wall? Is the wall isolated from the flatwork surrounding it with proper material? Unfortunately, I believe the answer to every one of these questions is "NO", and what you're trying to do goes against all "best practices" in the construction of a foundation and wall in a frost zone............


What's the worst that could happen?


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## oh'mike (Sep 18, 2009)

Worst case? The wall will start to lean---

I'm not a mason by anyone's estimation---so take this with that in mind.

Could you build a short block wall and then extend the height wiith a light er privasy screen?


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## BigJim (Sep 2, 2008)

If that were mine I would be checking with my insurance people to see what their specs are. It would be bad to go ahead and build a wall that they will not insure, then have to take it down.


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## almazon (Feb 19, 2012)

Heya guys,

I talked to few local guys and they told me that Frost Line here in SI is about 18-20" and I should be fine. Their only concern was that Concrete Blocks gonna lean, not the existing Poured Wall.

For this reason they advised me to drill a holes on top of wall every 2-3' and stick 1/2" rebar (4-5' long) and then, whatever block it goes into, get it filled it with concrete. 

Here is updated pics of Wall:


















BIG numbers - Height of the Wall, Small numbers - Depth.

Thank you in advance,
almazon


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## oh'mike (Sep 18, 2009)

Standing rebar is always a good plan---that will keep the blocks from walking off the top of the stem wall---and stabilize the wall--


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## almazon (Feb 19, 2012)

Heya guys,
My plans changed again 

I decided to go with PVC and I need your help with *HOW TO: Secure PVC Post On Concrete? *

Thank you in advance,
almazon


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