Retaining wall advice

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Old 06-24-12, 12:20 AM
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Retaining wall advice

So I started digging for a retaining wall along the backside of my property the other day. The ground is uneven and therefore the wall will be start off being 4 ft high and at the other end will be about 6 ft high. It's 50 feet long. I was planning to pour a 3" by 16" footer and placing rebar both along the length of the footer and also several about 2ft into the ground. I then planned to use 8"x16" blocks to build the wall. I was going to fill the first 2 levels of blocks with concrete where the rebars are. Here's my question. Today I had someone tell me that my wall would not be strong enough and I need to use poured concrete. Is this true? I thought I was actually going into over-kill a little with my plans. Oh and also the ends of the walls will have corners being built on them about 4ft into the yard. So basically it would look like this |____________| from above.
 
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Old 06-24-12, 04:12 AM
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Welcome to the forums! We don't know where you live, so any advice will be marginal at best. Fill out your profile. A 3" deep footing won't get it. You need to dig down past the frost line (depending on your location) and make a footing pour. Rebar laterally in the pour and vertically bent and tied to the horizontal ones so they will exit into the holes of your block. Your returns will aid in stability on the ends, but if there is backfill, you will need a return in the middle at one or more points, sort of like a dead-man to keep it from bowing your wall.
 
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Old 06-24-12, 05:54 AM
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This type of retaining wall requires a substantial amount of concrete to stay up. The footing will need to extend out in front of or behind the wall at a distance that is 2/3 the height. You will need rebar going from the footing up into the wall to the top.

A an easier option would be to install a segmented retaining wall. The footing is made from compacted base material. Depending on the blocks, they are either tied together with pins or they are shaped so they interlock when stacked. This type of wall remains flexible so it can move with the earth as it expands and contracts. They will also allow water to weep through the cracks of the wall to help resist hydraulic pressure.
 
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Old 06-24-12, 12:22 PM
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Your footing is too thin at 3" and obviously does not meet and code or standard. It should be wider than 16" (bare minimum for a plain wall in most places. The concrete is the cheap part when you consider the cost of excavating and backfilling.

If the wall is properly designed and reinforced properly, you will not need a deadman in the center. Make sure you use a well draining backfill and provide a means for the moisture behind the to drain away.

As drooplug mentioned, specially shaped segmental retaining wall block may be used without digging a footing below frost or pouring any concrete or grout. This type of wall will require a professional design since it is over 4' high.

Dick
 
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Old 06-24-12, 01:33 PM
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As the other posters have advised, your foundation is far too thin and narrow.
Take a look at the attached sketch from an old book on reinforced brickwork.
(The wall is of brick and is 8ft high, which is taller than yours but the principle remains the same).
Note how wide the foundation is; Drooplug commented on the need to extend the foundation to the rear or the front. In this way, sufficient bars can be cast in to effectively make the wall and footing as one. The weight of the earth behind the wall also helps to anchor the extended foundation down and so aids stability.
 
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