How to Build a Block Retaining Wall

Andrew Lein

Introduction

Any moron can build a retaining wall, and many have. Look around your neighborhood and you’ll see evidence. Missing blocks, leaning walls, weeds growing through cracks, and just plain ugly crap. However, in order to build your sturdy retaining wall, here are a few steps you can take to ensure a long lasting investment.

Are you ready to build a retaining wall?

-Steps to Getting Started

1) You'll need to be able to lift at least 75 lbs. at a time. If you can't, seek someone with muscle, or contact a professional landscaper.

2) Once your site and labor (if needed) are located, now measure the desired area or areas. Measure for height, width, length, and any curves or fancy designs the wall may have.

Materials & Tools

3) Determine what materials and how much of them you need.

• What kind of block?
• Flat faced or, angled, or round?
• What color?
• What quantity and what size?
• Will caps be put on to cover gaps left on top?
• Should those caps be glued?
• Base material-Gravel or dirt and how much?
  
• Rental of excavating equipment-Or just buy a shovel.
  
• Rental of a ‘tamper.’
  
• Erosion Control Fabric.
  
• Block Hammer. To 'tamp' the blocks level.
  
• 2 of 4 ft. Level.
  

Contruction Steps

Step 1 (Excavation)

- Dig out the foundation for your wall. Dig the approximately 2 ft. wide, 8 inches deep (Figure 1).

(Figure 1)

Construction Step 2 (Filling in with base material)

- Next fill the hole with your base material. Gravel is the best base to use. Dirt can also be used, but keep in mind this is probably a long term investment.

Construction Step 3 (Compacting)

- After filling the hole with base material, now you need to compact it. The easiest way is to rent a compactor, or ‘tamper.’ This gives the block a firm base to stand on.

Construction Step 4 (Laying Base Row of Block)

- After tamping, start laying the block. The first row will need to have the flanges broken off. Smack the block with a hammer, right where the flange and block meet. Set the block without flanges in the desired spot and take out your level. If one side, or the front or back is too high, SMACK IT with your block hammer. Hit the block until its level. Do the same for each block on the bottom level (Figure 2).

(Figure 2)

Construction Step 5 (Stacking Blocks)

-After your base course is laid, the rest is easy. Just stack the next row, off-setting second row of block 1/2 block over from the other (Figure 3).

Construction Step 6 (Placement of Erosion Control Fabric)

- After the 2nd or 3rd row of blocks, the erosion control fabric should be placed directly behind the wall so dirt cannot get through the cracks. Make sure there is overhang at the bottom, and fold it back so dirt can be placed on it to hold it in place (Figure 3).

Construction Step 7

- After laying the fabric, ‘back-fill' the wall. Just take the dirt you dug out from the base. Make sure it is compacted as you go, but just stepping on it this time will do (Figure 3).

(Figure 3)

The Aftermath

- After all the blocks are laid, step back, take a look, and see what you got. If you don’t like it, it can be taken apart. Its a hassle, but hey, you want this to last for a while don’t you? Be sure to return rented equipment, un-used materials, and the rest is easy. Clean up the sight, and whalla. Hopefully you have a retaining wall.

Tips, Hints, & Links

-Tips on Getting Started

Should I hire a professional? (Step 1)

-If you need to hire someone, they will first have to ‘bid’ the job. Price too high? Seek another contractor. Most people seek at least 3 bids.

-Some walls are for looks, others support hills, some have planting beds and/or flower gardens. Figure out exactly where and what purpose your wall is going to serve. Whatever you choose and how much you want to spend (keep in mind more block means more $money$) is up to you.

-Measurements (Step 2)

-If hiring someone, by measuring the wall yourself, this allows you to compare figures of total cost. If you have the numbers, then no one can screw you out of your money.

-Where and What Materials Should I Get? (Step 3)

-Most large hardware stores, such as home depot, carry landscaping supplies. However, going to a landscape material supplier might be better. Not only are they cheaper, but they can ad advice, and there will be displays on how final products should look.

www.timberwall.com

www.homedepot.com/home.html

Tips on Materials and Tools

-Most landscapers use 8 inches of base material to support the wall

-A tamper is used to compact the base material after it is laid. This will give your wall a sturdy base to sit on. They can be hand or gas operated.

-Erosion Control Fabric is put behind the wall and ‘butted-up’ against the back of the wall so dirt and weeds do not grow through the cracks.

-Block hammer, also called a ‘dead blow’ hammer, are made of rubber. If you use a steel hammer, it will chip, crack, and break your expensive blocks. Most are 5 pounds, but there are smaller ones.

-SMACK IT-This is done to make sure the base row is level. Otherwise, your wall might be a bit slanted, uneven, and ugly.

Stacking Tips

-The block is usually a foot wide, but ass the wall goes up, it steps back. Towards the top, the wall will seem wider. This is normal, the blocks rest on top each other and are supported in the back by a 1-inch flange.

Erosion Control Fabric

-Place against the back of the wall in an L shape. Leave overhang on the sides and top as well. When you have to use more than one piece, make sure there is overlap there as well. Dirt in cracks = ugly weeds growing through your wall.

Back-Fill

-An easy way to back-fill your wall is to use the dirt excavated for your gravel base. Also, startbackfilling as you get to the second or third row. If your wall steps into a hill, it will make it easier to fill-in as you go, rather than jam all the dirt in from the top (the space to be back-filled behind a wall gets smaller the highe your wall. More dirt is needed at the bottom thn at the top). See Figure 3.

Clean-Up Tips

-Spray the wall with water when completed. This will get rid of all the excess dirt, and it will make it look sparkley-clean and pretty for a picture.

Copyright© Andrew Lein
Last modified September 2001