Need advice on building a retaining wall...

In My Humble Opinion
1

So, I’m about to embark on my first major landscaping project…I want to put a short (maybe 1-1.5’ high) retaining wall along one side of my house, mostly to delineate a decorative flower bed. The wall will be about 30’ long.

From what I’ve read in the helpful pamphlets at Lowe’s and from the concrete block place I’ve been to, it doesn’t sound that hard…but I’m open to advice from anyone who’s done this before. Any tips and tricks I should know about? What will I need to buy to make the project go smoothly, aside from the blocks themselves and stone for the base/backfill? I know I need some stakes and string, a level and a shovel. Anything else?

What’s the best way to handle corners? Or should I go with curved ends? I think that the blocks I’m going to buy are tapered so that they can be placed straight or made to curve.

Am I getting in over my head here?

2

I certainly don’t think you’re going in over your head. Just remember to have a level handy, and level the ground before you start. Check level with each course of blocks!

In short, I have nothing useful to add, but I’m sure you’ll be able to do it. You’re pretty darned competent around the house, you’ll have no problem.

3

I don’t think you’re in over your head either. 1’-1.5’ is a pretty short retaining wall, so you probably shouldn’t have much trouble with it. One thing to remember, though, is DRAINAGE, DRAINAGE, DRAINAGE!!! The primary reason that most retaining walls fail (the big ones at least) is that they don’t have adequate drainage and hold water in the soil. Make sure that your wall is not watertight and don’t overwater the plants there, and you should be fine.

4

Pro Landscaper/ lite construction guy here.

No, you are certainly not in over your head. I will chime in and say level isn’t as much a concern as straight is. in fact a slight slope from one end of the bed is disirable as it can assist in run off during heavy rain.

Best way to attain a nice straight wall is to set one stone at your height, then measure out where the last stone in a straight line will go, set it’s height where you want it, then run a string that sits on the top of both tightly between the two. Place the stones on either compacted sand, or in your case (with such a short wall) plain ol dirt will do. You can adjust the height of the individual stones in the first course by adjusting the compacted sand base the first course sits on. Just give your string a little “twang” after you place the stones to make sure the string is just barely kissing the top of the stone you just placed.

Tamp tamp tamp, make sure your first course is sitting on a solid base, step back and eyeball your line to make sure it is going where you want. Taking a 2x4x8 and smacking the face of the bricks (like an 8’ long straight edge)will help keep them straight as you progress.

In an unmortared retaining wall all subsequent courses will follow your first course so if you get the first run correct you are home free. be sure to place the first brick exactly centered on the space between the two beneath it or it may bite you on the butt when you go to finish the ends. Half bricks are good for this but if you wind up a little off, a hammer can remove some material from the brick with ease.

Drainage is easy, plain ol gravel (not too fine) will work, a perf pipe imbedded in the gravel with a positive slope will work better. Not really too big a concern with the type wall you are planning, it’s not really tall enough to worry about and the butt joints drain pretty readily on their own.

Corners are up to you, curved or square its a matter of esthetics, square joints will line up better while curved ones will “overhand” or “underhang” a bit. Nothing major.

Other concerns to address before starting are “how will this wall effect the drainage of the lot?”, Does water still have a place to go? Also whatever you do, make sure your new soil bed does not slope towards your house and that the soil is a minimum of 6" below the siding of any structure.

I Hope I covered everything here. My tool list would include a flat tipped shovel, line level, torpedo level, wheelbarrow, a couple of buckets, masons twine, a short screed stick (1"x2" stick cut slightly longer than the width of you wall block) for spreading sand, and a 2x4x8 “helper board” for lining up the front and tops of the block. You may want a good pair of gloves if you are unused to handling masonry with your bare hands.

5

EvilGhandi, any chance I can coerce you to come over and build it for me? I can pay you in beer. :smiley:

Seriously, that was really helpful. I’m not too concerned about drainage, since the wall is intended to be more of a border to a flower bed I’m building than an actual functioning retaining wall, and the bed already naturally slopes away from the house…it just doesn’t have any demarcation from the lawn, it just fades into the grass. I was figuring that if I just follow the instructions in the oh-so-helpful Lowe’s pamphlet I picked up and backfill with gravel as I build, that should be enough.

I’m a little confused about how to make sure the wall is the same height at both ends…what does “set one stone at your height” mean? The lot doesn’t appear to slope along the length of the house to a major degree, and I know I’m going to have to excavate a long trench to put the first course of stones, so I can vary the depth I need to dig down to get the course level.

Oh…and what’s a line level and a torpedo level?

6

A torpedo level is a small one, shorter than your forearm, and often tapered at the ends.

A line level is a wee level the size of your pinkie, with teensy hooks on each end to hang on a string. If the string is tight, this gadget will tell you if it’s level.

Another old long-distance level trick is the water-in-tube trick. Get a clear, flexi tube a few feet longer than the wall. Fasten each end where you need to check, and fill the tube with water up to the line you want to mark. The water level at both ends will be the same height.

Now, of course, a laser level would make the whole thing simpler.

I’m about to do the same project here, and I’m nervous about it.

7

Sorry about the delay in reply. I’m in Hawaii and only post in the eves, its probably tomorrow already. My line of work makes it difficult to have computers at the workplace.

To clarify, what I meant by set a stone to your height was:

Determine how high you want the finished wall to be in relation to something else, ie the siding on your house, height above the grass whatever you are after in the finished wall.

Using two wooden stakes, tie one end of your masons line to a stake set by your height determining object. pound another stake near where you plan on setting the height of the wall. (corner point is good)

Attach your line level to the string and when the bubble is in the middle, there it is, your finished wall height.

Then using math or more simply a stack of brick, figure out how deep the groove you need to cut in the soil will be.

I recomend going an inch or so deeper and making up the difference with a sand base as it is much easer to spread smoothly than soil.

Then proded to the next step, that is walk down your trench and find the longest span in a roughly strait line as you can and set your second stone. measure it with a tape but dont be too concerned, if its a litte out of place you can scooch it over when you get there.

Like I said before level isnt really a big concern here, straight is. The tops of the stones should all follow a straight line or the finished wall will have a wavy, up and down roll. Sure sign of an amatuer job. An inch or so slope along the length is of no concern and may help with drainage.

The next real concern is that the stones are straight along their width. This is where the torpedo level comes in. Use it to make sure each block isn’t “leaning” in or out. This is very easy so spot by eye in a finished wall but hard to see when you are right there placing brick.

Remember to step back every few blocks and eyeball the wall as you progress. if it looks a bit crooked, rap em with the 2x4. Ive found this really helps for small adjustments.

Hope this helps.

8

Sorry, forgot to include that if you want the wall to be level, that is same height at both ends, you can do it with the line level as well. Just attach it to the string when you set your second block. After that its a matter of adding or subtracting sand under the block till the bubble centers. Repeat the process as you go.

Some other tips.

Make sure nothing gets under the string, keep checking, I had to dimantle about 20’ of mortared block a few weeks ago because a 1/4" stone got under my line.

You can even out the blocks by “stuffing” sand under a corner rather than lifting the whole block and re-screeding the base.

Retainer block is heavy, have it delivered and save your suspension.

Don’t be discouraged, this is a simple masonry project very suited for the do it yourselfer

9

I was going to attempt this sort of project, but EvilGhandi has just scared me out of it.

Could you re-post those instructions, step-by-step, using language you would use to talk to a 3-year-old? Pretend I don’t know what “screed” means. Because it sounds to me like you want us to first set one stone at one end and the second stone at the other and then fill in so everything is straight and level. That doesn’t make sense to me. Nor does “level doesn’t matter, straight does. The tops need to be straight…” (Wouldn’t that mean the whole wall is level?)

Anyway I’m just really confused and will now procrastinate doing this project for a couple years.

10

Sorry, not trying to scare anyone. This is really a simple project That anyone of reasonable handiness can pull off. I am just tossing out a few methods us pros use to get, well, professional results.

Ok lets clarify a few terms.

Picture a glass window looking over the ocean.

Draw a line across the horizon using the ocean as a guide. That line is level.

Now measure up one inch on the right hand side, using a stick, draw a line from the left to the right. That is a straight line.

The reason you set to stones and fill in between is so you can easily line the tops of your blocks straight, that is no up or down “waves”. If that makes no sense you can just as easily pound a stake and measure where the brick will be and tie your string to it. Me I just use the brick, I know it’s the right height.

Don’t be discouraged, it really isn’t as complicateed as I made it sound, there just are a couple things to watch for.

11

Oops forgot to define screed. Scree or screed is an industry term basicly meaning set a surface to a uniform height usually using a board as a straight edge.

What I meant in this case was to lay your sand into the ditch, take the little piece of wood, drag it to and fro until the sand is all smooth. Gives a nice, even footing to set the stone on.