# 4' CMU retaining wall.



## ruskent (Jun 20, 2005)

I am interested in building a 4' tall cmu retaining wall on a project. I have a engineered drawing for a similar wall that we did not build. The engineer is calling for a T footing. The botton of the footing is 4' down. Frost line here is 3.5'. Then he wants 2' of the cmu below grade. Then 4' above grade. I have never built a masonry retaining wall before. But it seems to alittle odd to me to have 6' of concrete below grade.


Does this seem right or does the engineer have no idea what hes doing? There are no extrodinary surcharges on this wall either.


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## tgeb (Feb 9, 2006)

As you describe it, it makes perfect sense to me.

The only thing missing is a sh*t load of rebar.


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## ruskent (Jun 20, 2005)

LOL yea there is a ****load of rebar in it


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## dakzaag (Jan 6, 2009)

Not so sure I would go with 4" no matter how much rebar you put in it. And most 4's would need to be punctured on the top since the core is almost always filled in at the top. 

Strength wise a 6 or 8" would be much stronger and stable for a small increase in cost. 

I would put dead man anchors in also for frost heave.


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## rbsremodeling (Nov 12, 2007)

I would form and pour a 4" wall instead of laying block


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## stacker (Jan 31, 2006)

i could blow a 4 inch wall down with a decent fart.i wouldnt build a retaining wall with anything less than an 8 inch block,filled.


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## concretemasonry (Dec 1, 2006)

Rusk -

If you are using block with mortar and possibly brick veneer, you should be below the frost level. This is not the height of the wall. It is the depth of bottom of the footing below the the lowest area of the finished grade,

If you want to offer something else, propose a concrete segmental retaining wall (SRW) system that does not require a footing below frost and is NOT permitted to have mortar or a concrete footing. This system is designed to allow minor movements of the wall and better drainage of the retained soil. It is far more popular and common than a rigid wall with a footing. Walls can be built up to 45' without footings, but engineered using geo-grid to reinforce the block of soil behind the wall. - Most local municipalities have standard design plates for municipal projects or private applications that provide details for walls under 4' high. The walls can have either inside or outside corners and can easily be adjusted for grade changes. Many different faces, textures and colors are available to match the commonly used concrete pavers. - You still need a level, at least for the critical first course and then it is futile unless your eye tells you so or you screwed up on the first course set on compacted gravel.

Block producers feel bad about selling a product that competes with the traditional block/brick and mortar, but the market is so much larger it is impossible to ignore the success and huge volume. The reputable common systems are used internationally and there are plants that only produce the units 24 hours per day through much of the year. I saw an international project that had about 7 miles of walls from 2 to 45' high on both sides of the highway.

Not a product for the craftsman, but a good product for many different applications.


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