Do I need to secure concrete block ?

[Mudball]

 
https://i7/photobucket.com/albums/y267/Mudball/Picture034.jpg

This pictures shows the footer next to the deepest wall of dirt where there will be a concrete block wall placed. By the way the lines are where the water and electric will be entering. This deepest place will have about 5' of dirt high. However the space between the concrete block wall and the dirt will be backfilled with gravel. I also want to strengthen the below grade block wall with something like a 1/4" thick Quickrete 5000 spread over it and then seal and then gravel backfill.
Most of the other dirt around the house will be approx. 3' down to nothing in the front. With the deepest part being around 5' deep (half of that is undisturbed dirt) and then backfilled with gravel my question is would you do anything special to the block to secure it ?
The gravel will help from any freeze heaving ect...
There is no vertical rebar...too late for that.
Should I pour the first few layers of block with concrete or is it really necessary ?
There will not be a concrete slab poured on the inside against the block for maybe until next spring/summer.
If I do nothing to the block but have them just stacked and mortared together then should I wait to backfill between the dirt and wall until after the slab is poured ?
Thanks

[glenn-k]

I believe it is nearly imperative that you put vertical rebar in and horizontal rebar in for a retaining wall, Mudball to keep the backfill from pushing the wall in.

You can drill with a rotohammer - rent it - and insert vertical rebar and epoxy it in -block has very little strength by itself so will need grout fill.  Waterproof the outside also.

I suggest you check a procedure book or with an engineer.  Try the quikcrete info in our links.

Couldn't get to your picture - sorry I can't be more clear today- gotta go to work.

[jraabe]

It is sometimes amazing how much force a few feet of height can exert on a retaining wall.

There is an excellent article in the Sept. '05 issue of Fine Homebuilding Magazine (http://tinyurl.com/8wleh), This is a scan of the example cross section through a concrete retaining wall. These are usually poured concrete but short ones can be made with concrete block and bond beams. Either one should have solid steel reinforcing tied back into the footer to act as a counterbalance to the sidewards forces.

Anything over about three feet should be designed by a local engineer, especially if it is to supporting a patio or other useful living space.



The article also has less expensive ways to do retaining walls such as PT timbers, stone and modular (self-locking) block.

[Daddymem]

SRWs (See http://www.versalok.com/primarysite/whatAreSRW.htm ) have become much more competitive now that they have beaten the bad rap from past years.   Much about these walls has just recently been learned and now, with proper installation, they make a much better alternative than the concrete retaining wall as shown above.  With the newer colors and finishes we engineers are even able to satisfy ornery architects.

Retaining walls are both the wall itself and a wedge of soil behind it. Take that wall cross section above.  Start at the base of the wall and draw a line all the way up to final grade equal to the angle of repose (angle the soil naturally won't cave in at) for your particular soil (say 45 degrees for arguments sake).  That is the wedge of soil you will be holding up with the wall, this acts as one single mass.  If you extend geotextile fabric out behind the wall you break that one wedge up into a bunch of smaller wedges starting at the intersection of the fabric and the wall.  Situations vary, what is above and what is below the wall?  Compaction and drainage is very very inportant behind retaining walls.  Retaining wall failure is soooo very common, usually due to improper construction techniques or poor specifications and plans.  Also remember, terracing 3-4 foot high retaining walls doesn't get you around needing a structural engineer; if they are horizontally close enough (angle of repose again), you still have one wall.  Underestimating this can be catastrophic.  
Here is a company with some interesting literature (Check for local suppliers, these are the big guys in our area): http://www.versalok.com/architectengineer/aLiterature2.asp
 My company was involved with site design on this project: http://www.versalok.com/picts/shawsSm.gif

[Bart_Cubbins]

I agree with the opinions above that these are retaining walls and should have lots of vertical and horizontal reinforcement. Just have one thing to add... Build your first floor deck before you backfill. It will provide a lot of additional strength by bracing the top of the wall.

Bart

[Bart_Cubbins]

Some concrete block details can be found at http://www.masonrydetails.com/. Clicking on "Details/Map" and then on Washington gets you to http://www.masonrydetails.com/details/?region=wa

Check out the details for "Foundation" and "Bond Beams". Here's the one from "Ret Wall"...



Note that for a foundation wall where the top of the wall is being braced by the floor deck, you'd keep the vertical rebar in the center of the block cores.

Bart

[Mudball]

Thank you all very much.
I read and checked out all the links and then when on to other links and then more links.
I will make SURE there is reinforcement in the walls.
Thanks again.

[Amanda_931]

Also think about drain to daylight in back of that wall.  Maybe cut the room up with a small buttress or two on that back wall.

This is the house wall not a retaining wall, isn't it?

[Mudball]

Sorry it took so long for reply. Backhoe dug through phone line thus no internet. Waited on phone company no longer. Went outside this morning and temporarily fixed myself.

Yes Amanda_931 it is a house wall.
I just met with the guy who works for the people who sell the block...not the blocklayer. He did all the measuring for wall height, windows ect...
He said (He's the third one that has seen the site and giving opinion on reinforcement) that as long as I'm going to be backfilling myself by hand with washed gravel then I will be fine with 8" block (without reinforcement). He had more to gain ($) by trying to sell me 12" block instead of 8" but didn't and was giving his honest opinion. He also said that if I lived in the neighboring county then I barely have enough backfill height for codes to require 12" block even though half my dirt is not disturbed. Even though he said I would be fine with 8" block (with no reinforcement) I'm 99.99% sure I'm going to use the 12" block.
 
If you don't mind Amanda could you send me a message as to where you live in middle TN. ?
Thanks

[glenn kangiser]

Last year I jack hammered out a 3 foot high retaining wall with reinforcement and drains behind that moved as a unit 10 feet or so into the back of a mans garage.  I think his drains may have sealed with clay and water built up behind it.

As Daddymem, Bart and John said, forces behind a retaining wall can be great-especially when backfill is loosely installed.  It all turns to mud.  Roof rainwater runoff in a storm can amount to 1000's of gallons. For mud lets make a few rough rule of thumb calcs.  The engineers can tell you how far off I am.  Estimating a 45 degree angle of repose on a 5 foot wall I'm guessing that 1/2 the weight of a 5x5 square section (triangle) could push against the base of the wall, or 12.5 cu. ft. per foot.  Estimating the weight of mud at 150 lbs per cu. ft. I think you may get a pressure of about 1875 lbs per running foot of wall if it was all to turn to mud.  20 feet of wall could have a force of 37500 lbs against it.  20 feet of 12" wall not tied into the floor weighs 15000 lbs rule of thumb estimate again.  I wonder which one will win if possibly a truck or something drives to close to the house when the ground is saturated and this thing decides to break loose.

Possibly the guy is right and you will never have a problem.  It just seems you would sleep better during storms, etc if you knew your retaining wall wasn't going to move in with you.

Okay -I had to edit due to a brain malfunction on my numbers but now its better. :-/

[PEG688]

  Bart I'd put some verticals in say,, every two feet or so .  Lay your first course of block and every couple of feet roto hammer a 5/8 hole into your footer and drive in a 2 foot long piece of rebar , go up one more course and then fill the holes,,, with mortar ,, in the block where the steel is .   That's what I 'd do any way .  Better safe than sorry,  ;)Good luck with your project :)HTBH  ;)PEG