MMH
Gold Member
I need to build a 8 foot tall retaining wall. What is the most cost effective construction method?
8' Retaining Wall
- Thread starter MMH
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MikeInEburg
Veteran Member
MMH said:
Eight feet is fairly high. If it must be straight up, you'll need a high quality design as well as safety rail at top. Better would be a terraced arrangement.
Mike
forgeblast
Elite Member
versa lock? the base is going to be very important.
Chuck Oppermann
Member
Just curious, is the ground level that it is holding back, or is it on the side of a steep hill and trying to hold that back? Is the ground sandy or solid. What is on the down hill side of the wall? I think we need information on what the surroundimng conditions are before an adequate responce can be given.
CurlyDave
Elite Member
In every jurisdiction I know of, an 8 foot retaining wall must have the design stamped by a registered engineer.
Most places 4' is the absolute maximum for a self-designed retaining wall, some places it is 3'.
The main reason for this is that the forces on a retaining wall increase as the cube of the height. An 8' wall is only twice as high as a 4' wall, but has eight times the overturning force.
In Oregon, my neighbor had a self-designed retaining wall which fell down in its first winter. I tried to show him a better design, but he insisted on having a guy with a backhoe come out and re-stack the 2'x2'x4' concrete blocks, and it fell down again in its second winter. The third time he was more willing to listen and the wall was restacked in a different manner, which has been stable for several years.
Most places 4' is the absolute maximum for a self-designed retaining wall, some places it is 3'.
The main reason for this is that the forces on a retaining wall increase as the cube of the height. An 8' wall is only twice as high as a 4' wall, but has eight times the overturning force.
In Oregon, my neighbor had a self-designed retaining wall which fell down in its first winter. I tried to show him a better design, but he insisted on having a guy with a backhoe come out and re-stack the 2'x2'x4' concrete blocks, and it fell down again in its second winter. The third time he was more willing to listen and the wall was restacked in a different manner, which has been stable for several years.
hr3
Veteran Member
Well Curly Let us in on what his "yours" last design was that worked
jdonovan
Gold Member
I'm a fan of keystone wall units. They stack with out mortar, and interlock with fiberglass pins.
Here we need a permit if we go above 2'. So my walls are built as terraces. 2' wall, 3' setback, and then another 2' wall. Repeat until tall enough. With a 150% setback the county views them as separate walls. Therefore each may be 2' tall without permits. This also assumes a flat surface behind the wall for 150% of height.
An 8' wall has HUGE overturning forces. I absolutely would not attempt to build one with out an engineered design.
I did build a 6' wall and the design required a geotextile to tie the block into the hill every 2 courses and the tie back was 6 - 8' long. Every 6" of backfill had to be compacted to 95% density. It was a huge project and I'd really not recommend it to a novice wall builder.
The county was highly skeptical of a homeowner doing this work, but I took my time did it right, and 8 years later it and all my other walls are still standing, no settling, or creep.
Army grunt
Platinum Member
I built several in Ct. an had good luck with 6x6 pt.The trick is to build in dead men into the wall, also back filling with tires & crushed stone with drain pipe. In the north your fighting the frost, then the heavy wet soil of the spring thaw.Plan ahead an the walls will work great an stay.There are walls still straight an where i put them over 20 years ago
Army Grunt
Army Grunt
Steve_Miller
Veteran Member
We produce these products, may be much larger than your looking for.
Retaining Walls : Shaw Pipe
Steve
Nova Scotia