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Interlocking Block Wall and Stairs Using concrete pavers to create a wall with the look of natural stone From "Rock Solid" episode DROC-201

(Continued from page 1)

With the excavation compete and the footing prepped, it's time to begin setting the blocks. The first row of stone is the most important row as it will provide the foundation for the entire wall. Work begins by setting stretcher blocks at the lowest elevation of your wall.

Our wall is built in three parts:

• a segment leading from the house to the stairs;
  
• a wall segment leading from the street to the stairs; and
  
• the stair unit itself.

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	Figure M
	Figure N

Building Up the Walls and Corners

• Continue setting your first row, leveling each block side to side, front to back--and with its adjacent blocks. This is where the different sized levels come in handy. If your grade gradually slopes, you may want to rake out a more level footing with a landscaping rake. If you rake, follow by tamping the disturbed footing. You can individually finesse blocks by leveling the footing with your trowel and pounding the blocks into place with a rubber mallet. This is the most painstaking but important part of the wall, so take your time. The subsequent rows of block will be much easier to set than this first one.

• Only one course of block should be below grade (figure M). As the elevation shifts upwards on this project, your first row might disappear into the grade. To keep the row of block level and only one course below grade, allow your first row of block to be buried into the crusher run and then begin a second row on top of it. This second row then becomes the first level buried below the grade.

• Finish setting the first row. If you have a stair unit, create the stair returns. You'll create the walls on either side of the stairs before creating the stairs. This specific stair unit tapers from about six feet wide at the driveway to a walkway about four feet wide. Derek marks out the area with inverted marking paint to determine the edges of the wall (figure N). Once that has been marked out, build the corner of the wall. The corner block should be set with its two rock faced corners exposed. The block adjacent to the long, unfinished side of the corner block should be a full cap. Corners are created by alternating un-grooved corners. Setting full caps ensures that all of the blocks will fit on the wall.
  

  	Figure O
  	Figure P

• With the first row or "course" of block completely set, begin setting the second course (figure O). If your wall has two sections like the one featured in this project, you can work on the sections simultaneously or finish one wall before starting on the other.

• The second row of block is also made up of stretchers. The grooves on the bottom of the blocks will fit on top of the tongues of the first row. Each block in the second row should be centered on top of a joint between two blocks in the first row. This process of breaking up joints is called creating a "running bond." Any gaps created by breaking the joint can be filled with half-sized cap pieces or by pieces cut with chisels or saw.

• Build the second row all the way to the stairs. Use the stretcher blocks until you reach the corner and then place the corner so that the long face of the block is exposed. This will break the joint of the full cap and corner beneath it and maintain the running bond. Place a full cap next to the unfinished edge of the corner. You'll continue this process of alternating faces--called "toothing"--as you build up the height of your wall.

• The corners, because they don't have the tongue and groove system to keep them in place, should be secured using the retaining wall adhesive (figure P). You don't need much. It's a very strong material.

  Rock Solid Tip: When setting the corner, press the block down into the adhesive, lift it up, let some air underneath and push it down again. This process helps the adhesive set faster.
  

• After you've built up two courses of block, spread landscape fabric behind the wall on top of the footing and against the earth that will be retained (figure Q). This fabric keeps soil from washing into the crushed stone drainage area behind the wall. Overlap the layers by at least two inches and secure them into the retained earth with twelve inch landscape spikes (figure R).

  Figure Q

  Figure R

  
  

• Cut the layers long – they will fold over the crushed stone at the finished wall height to protect the drainage area (figure S). Secure the fabric at the base with 3/4-inch crushed stone, added to just below the height of the two courses of block (figure T). Tamp that 3/4-inch crushed stone to prevent settling.

  Figure S

  Figure T

  
  

  Figure U

• Run the perforated PVC drainage pipe on top of the crushed stone (figure U), and make sure that it pitches downwards away from the house or standing structures. The water should also have an area or gap in the wall to drain out.

• Continue adding courses of block till you reach your desired height. There should be no gaps in the faces and you should attempt to keep the running bond of the wall. Every two courses add ¾ inch crushed stone behind the wall and tamp. Adding and tamping crushed stone in layers minimizes settling after the wall is completed.

• As you add height, you'll notice that the face of the wall tilts backwards slightly. This is the "batter" of the wall and where the product's name "Roman Pisa" comes from. It adds strength to the wall by leaning into the retained earth.

• Repeat this process of building up height and adding stone until the very last course of concrete blocks. The last course should be made of full cap blocks (figure V). These will fit into the groove of the stretchers below them, but allow you to place the coping caps for accents on top of the wall.

• If your wall steps down in height--like Dean and Derek's did as it ran towards the driveway--the last block in each row should be a corner stone set on top of a full cap in the row beneath it (figure W). You'll need to secure these last stones with retaining wall adhesive.

  Figure V

  Figure W

  
  

  	Figure X
  	Figure Y
  	Figure Z

With both walls built up and ready to be capped, add the stairs to your project. This project's stairs will meet an existing walkway at a higher grade. Hold a string at the highest point of the steps and have someone stand at the bottom of the steps holding the other end (figure X).

Level the string, then pitch it slightly downwards. (You'll want water to pitch off of the steps.) Then measure the distance from the ground to the string (figure Y).

The measurement for this wall is 30 inches. Steps should be built at a comfortable stepping height of between six and eight inches. Thus, Dean and Derek build five six-inch-tall steps.

Once you've determined the number of steps, mark out their placement in the dug out earth with the inverted marking paint (figure Z) and test them out to see if they are a comfortable stepping distance apart. If the steps fan like ours did, now's the time to incorporate that curve.

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