Heavy Stone Retaining Wall

Posted on March 24, 2017 by Simon

Contents

The Video
Cost
Engineering
The Gallery

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…

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.
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.
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.
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.
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.

Here is the delivery. I paid 80$ per pallet, plus something (like 120$?) for the truck to deliver all the pallets.

Here are some more standard concrete retaining wall blocks. If you check the top right, you can see how many linear ft you get per block and calculate how many square ft of wall you would get per dollar. When I compared this with the cost of my quarried sand stone, my sand stone was about half the price.

Before I could bury the garage, I needed a retaining wall, but before the retaining wall, I needed some stucco over these fox blocks… This is just the scratch coat.

Partway thru the stucco job, I checked to see if the camera was still on. This is apparently how I look after a couple hours of night stucco work. (after finishing my regular work day and driving out to the site).

To get a gentle curve, I put down a 20ft long piece of 1/2 inch PVC going thru the marks I had made earlier. Then I put down mortar and started laying blocks.

After a few rows, the wall was already looking interesting and I was already learning.

After the wall was a few blocks high, I back filled for drainage. I also covered this all in landscapers fabric to keep the sand out. Actually, I came back later and filled the whole area with drain gravel, it is easy to use too much when you have a skid steer bucket and order by the dump truck.

After dark it starts to get harder to find the right stones. This evening I probably only got 3 layers in.

The 3rd evening, I got another 3 layers in before it was too dark to find rocks…

The rocks were all aligned against the front of the wall, but the back looked considerably messier. To sort that out, I used my mortar sprayer to shoot mortar over the back of the wall and fill all those cracks. I did it at several stages, this was the first. No pics of the actual shooting because I was busy at the time.