How to Build a Seat Wall

Walls are great to define spaces and give backdrops to plantings. Low walls (16”-20”) also double as great seating areas.  Cinder blocks are 8” tall, so two on top of each other is 16” and then a stone cap gets you to 18”….perfect!  Here are our cheap and easy wall construction tips!

1.) Prepare the area where you would like the wall.  We like to dig a 1’ wide by 6” deep trench and fill it with decomposed granite (the orangey pink gravel-like substrate).  Make sure to get the granite in as level as you can.  Tamp until firm, and hose it down to really make it set up.

2.) Wait about 30 minutes and then begin your first course.  Cinder blocks are 16” long, so if you want an 8’ long wall (96”) you’ll need 6 cinder blocks for your first course.  A string run parallel with the ground will help you keep them in a straight line, and be sure to take the time to get all of these blocks level by using a 36” long level and moving block to block.

3.) Once the first course is set and level, begin work on the second course.  For strength, the cinder blocks need to overlap, but this will leave you with an 8” gap on either end.  Not to worry, most hardware stores carry a half block (8”x8”x8”) which will fill in these gaps.  Cinder blocks aren’t perfect, so you may need a shim here and there to solve any blocks that wobble.

4.) For added strength, we like to hammer in 24” long pieces of rebar (the 3/8” diameter is fine and easy to find) in every other hole (cinder blocks have two holes) until they are 1” below the top of the block.

5.) Now fill up all of the holes with decomposed granite.   Tamp it in with the end of a hammer, soak with water, and then refill with more decomposed granite until full.

6.) Since this technique is not done on a concrete pad, over time the cinder blocks will shift a bit in our soil.  Therefore, facing the cinder blocks with stucco is not recommended because it will show cracks over time (if you want to do stucco, replace step 1 with a concrete beam of the same dimensions).  What we like to do, is to put a stone façade on the blocks.   Most rock yards carry thin moss stone or true veneer stone that is used in these applications.  We have used both materials here at the store. You simply put a little of the thin set on the back of the rock with a trowel and them press into place.  Work from the ground up and with a little patience, (and you puzzle fans will have no problem) you can get a very neat mosaic of stone as your façade.

7.) Ultimately, you’ll want the stone façade to be finished flush with the top of the highest cinder block.  If you are using irregular-shaped stones for your façade, your stones may extend higher than the top of the cinder block.  Once they are secured to the wall and the thin set has dried completely, you can then come back with a stone grinder (about $100 at hardware stores and make sure they have a masonry blade) to cut the tops off even with the cinder block.

8.) To finish the project, use a smooth stone as your coping (the section where your butt sits on).  Most flagstones work great for this.  Again, use the thin set mortar to attach these in place.

And voila!  You now have an awesome stone seating wall!  If any of these steps are confusing, next time you’re in, grab Peter, Eddie or Adam and they can walk you through it.  With materials on hand, this is an easy weekend project that will add a dynamic and functional feature to your landscape.

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How to Build a Seat Wall

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