Retaining Walls

How to Build a Stack Stone Retaining Wall


Stack-Stone Retaining Walls

If you’ve ever wondered how they build those nice stack-stone retaining walls, I’m going to show you how right now. It gets started with a concrete foundation. So what we’ve done here is adjust for the elevation change.  This wall begins at the corner of the house. It’s about 5 1/2ft tall. It carries on through the elevation change. This wall’s about 35-40ft long. At the very end of this was going to be about 8-10inches tall.  So we start off at a higher elevation and end at the lower elevation.

At the foundation, we’ve begun by pouring a concrete foundation. This is going to have to step up on the bottom to adjust for the change in slope; so it actually rises in steps.  Let me try to get a close up of that.   Here’s one of those steps right down here in this hole. You’ll see this concrete foundation is poured at a depth of 6inches thick, and we step it up to adjust for the grade. Otherwise, this whole entire wall would just be excavated, out and then we’d be burying our good stone.

Foundation Prep

One note, behind this wall you’ll see that the foundation is black. That’s actually been painted with a waterproof tar coating to waterproof the foundation of the house where we’re going to be backfilling with new dirt and new soil. We set the structure of this wall out of concrete masonry units (cinder blocks 8inch x 8inch x 16inch). In the core, we filled every fourth core.

So, we’ve got a core filled with it has a 4ft deep piece of rebar in a steam rebar to tie this whole wall together. we filled every fourth core with concrete, and then along these joints, we secured them with a type-s masonry mortar.  So that’s going to hold everything together. We also have brick ties on this wall. These are metal ties you can get at a brick yard. As this wall is being set vertically these ties are going to hold everything tight to keep that from ever falling over.

Hand Chipped Stone

But here’s where the real work begins.  What’s going on behind me is these masons are chipping the stone. Not just some of the stones, but every single piece of stone. This is the detail work that goes into making a wall look crisp and beautiful, and I’m going to show you a section of it that’s already been finished. Right here you can see the face of the stones are all hand chipped. It just gives it a much nicer appearance rather than taking the stone rough off the palette and trying to build a wall.

Here’s an example of a hand chip stone. It takes about maybe 10 hammer hits per stone, but really these guys are going to be sitting out here for a couple of days doing nothing but chipping stone, and then this stone mason is going to be doing nothing but setting them vertically.

String Lines

So, let’s talk quickly about how we set that vertically. Here’s a just a really cool shot that I can give you. You see we’ve got these wood boards set up. These are guides for us. We set a string line that’s approximately 5 inches off of the face of the wall. We’re doing what’s called a dry stack. In a dry stack, I’m going to put the mortar behind the stone, but we don’t want it coming in between the joints of the stone. We want to show off the stone veneer itself without having mortar squeezed out. So we set it about 5inches off (the thickness of each stone is roughly around 4inches) so we’re having about an inch to inch and a half behind of mortar behind the face of these stones.

So the mason set up the string length, and this serves as a guide.  Here is another yellow string line that you’ll see this is our plumb guide, our vertical guide. So off of this horizontal string line, we’ll set a vertical string line because this keeps everything square as we move up the face of the wall. It’s really noticeable when you don’t do this.  If don’t, you’ll see wavy joints across the face of the wall and that just looks bad when it’s done.  So setting the string lines allows us to stay horizontally level and vertically plumb.


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