Heavy Stone Retaining Wall

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Posted on March 24, 2017 by

When you are burying a house, one of the tricky bits is to keep the dirt from spilling where you don’t want it…  Like into the doorways.  I have a number of retaining walls planned for this build, and, just to keep things interesting, I have designed each one a different way.  This section is about the “Heavy Stone” wall by the back door/patio.  More details below, but first…  the Video

The Video

Cost

I had assumed that those concrete blocks were the cheap way to build a retaining wall and the fancy quarried sandstone was the expensive way.  Of course, I probably still would have used some real stone…  However, when I looked into it, At least for the cost of the stone, the real stone was cheaper.  Of course, that doesn’t factor in things like the cost of the mortar, which was about 5$ per level on my wall, so still not too bad.  The real cost of building a wall like this is time…  Those precast concrete block walls probably wouldn’t have taken me nearly so much time, but no regrets on choosing to do this one the hard way.

Engineering

Retaining walls often fail.  Keys to keeping this one from going down included…

  1. Wide heavy stones (heavy stone is actually what they called this size at the quarry) that are substantial and want to stay where you put them.
  2. Leaning the wall back against the earth load.  Before the earth can tip your wall over, it would first need to straighten it out.  Gravity helps you keep things as they are.
  3. Curving the wall against the earth makes it a lot harder for the earth to tip it over, just as it is harder for a mug to tip over than for a domino.  Making the wall concave helps even further because the loads against it are in compression, something that the stone handles with ease.
  4. Behind the wall, I had plenty of drainage.  Drain gravel, landscaping fabric and HDPE corrugated/perforated drain tube were working to make sure that water pressure never gets a chance to build up behind the wall.
  5. Layers of carpet were also used in the dirt behind the wall.  This “geo-textile” idea is used by highway engineers to keep dirt from shifting under ramps.  I would have liked to have used more layers, but some is better than none.

 

I watched lots of videos online about how to build a retaining wall that lasts.  I recommend anyone who is planning to build there own do the same, and don’t be tempted to take shortcuts.

The Gallery

Here is a gallery of pics with detailed captions.

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