Okay, so you've taken my advice and built (or at least planned) a "raised" railroad. Now you have to figure out how to get your towns and forests the same height as your trains. The most common backfills used to raise the apparent "ground level" of garden railroads are dirt and gravel. To hold the backfill in place, most garden railroaders use some kind of retaining walls, generally made of wood, stone, or preformed concrete blocks. Of course, each of those materials is available in a wide variety, some of which may not be affordable or even available in some areas. So this article is largely a review of basic principles that affect any retaining wall/backfill project, with some notes about advantages and disadvantages of specific kinds.

Note: Most landscapers face most of the same obstacles as garden railroaders when designing retaining walls. As a result, all but one or two of the examples discussed on this page are visible in parks, front yards, and even near restaurant entrances where you live. So don't wait until you see a bunch of garden railroads to decide what kind of retaining walls would look good supporting your own garden railroad. Observe the dozens of non-railroad examples you pass every day and decide what look would most suit your back yard, your skills, your tastes, and your budget. In fact, several of the photographs in this article are not from garden railroads at all, but from raised vegetable gardens or city businesses that tried to dress up their space a little.

The following topics are discussed in this article:

• Backfill Options
  • Dirt
  • Gravel
  • Calculating Backfill Amounts
• Wall Issues
  • Rigidity
  • Drainage
  • The Wall as Transition
  • Costs
• Wooden Retaining Walls
  • Railroad Ties
  • Landscaping Timbers
  • Fence-style Construction
• Stone Retaining Walls
  • Loosely Stacked Stone
  • Tightly Stacked Stone
  • Building a Stacked Stone Wall
• Concrete Product Retaining Walls
  • Landscaping Blocks
  • Poured Concrete Walls
• Cosmetic Treatments for Retaining Walls
  • A Wall Over a Wall
  • Concrete Cliff Veneer
  • Scale Model Walls
• Conclusion
• Reader Feedback and Tips

Backfill Options

The first part is relatively easy. For backfill, you basically have a choice between gravel only, or dirt and gravel.

• Dirt - If you want plants to grow around your trains, your backfill needs to include dirt. If the dirt is on top of gravel, it should be at least a foot deep to support most groundcovers suitable for garden railroads, or two foot deep to support dwarf conifers as well. The dirt doesn't have to be very good - if you plant something that needs excellent soil, buy a couple bags of good dirt and use around those particular plants. But for most of your garden railroad, anything short of pure clay will suffice. After all, you don't want your plants to take off and constantly need trimmed or moved. When I ordered dirt for the first loop of my garden railroad, the New Boston and Donnels Creek, the fellow I bought it from said it was "mostly topsoil" that had been scraped from a vacant lot that was going to be used as a building project. My take is that it had more likely been scraped from a cornfield, and was pretty low in nutrients. But that was okay with me. I can always pour some Mir-Acid on my Dwarf Albertas if I don't think they're growing fast enough (generally they grow more than I want them to, anyway). When I extended my railroad, I used a mix of clay and topsoil (mostly clay) from one of my own building projects to raise the level of the next section. With the exception of a few square feet that won't support most ground covers (although they do support dwarf evergreens and dandelions), that hasn't caused me any serious problems.

  When you try to buy dirt, you'll discover quickly that, while dirt itself may be "dirt cheap," having it hauled to your place costs real money. So you don't want to order a tad too little and wind up paying way too much for a little more to "top things off." Just how much dirt you need depends on how many square feet you are raising, how high you are raising it, and how much of your backfill will be gravel. But don't bother paying a premium for the "best" topsoil anyway. Even if you knew you were getting great topsoil (and not river silt or any of the other products they sell as topsoil), it would be overkill for your railroad. Note: To figure out how much dirt you'll need, see the Calculating Backfill Amounts section below.
  
  

• Gravel - To assist drainage, plan on pouring several inches of gravel against the inside of each retaining wall, especially if it is wooden. If the "base" of your railroad is in an area that occasionally gets standing water, you might consider a few inches of gravel under the whole "base" of your retaining wall as well. Some folks have used gravel for most of their backfill, and used dirt only in specific places where they planned to put plants. (This is most common in very dry climates where folks going to drip-irrigate on a plant-by-plant basis.) Whatever you decide, do not buy pea gravel, "river rocks" or other gravel with rounded edges. It will never stabilize, and it may contribute to other parts of your railroad failing dramatically. One bad example of misuse of rounded rocks occurred to some friends who used those trapezoid-shaped landscaping stones to build a very large bathtub-shaped wall to support their railroad. The railroad was over thirty foot long and over three foot high at one point, backfilled with rounded gravel, and with very little provision for drainage. After one very heavy rain saturated the "bathtub," the water pressure "blew out" one side of the wall. A good proportion of those rounded stones poured right out into the yard, spilling out of their enclosure as freely as they had spilled off of the truck, and taking track and buildings with them. With crushed gravel, the whole thing would have been far more stable; even if part of the wall had fallen out of place, most of the railroad would have remained intact.

Calculating Backfill Amounts

Backfill is usually sold by the cubic yard, which is 27 cubic feet of dirt. This sounds like a lot if you're talking about trunk space, or even mulch (which you only spread a few inches deep, after all). But a cubic yard of earth will only raise a 5'x5' square area by about a foot.

You probably won't get a precise measurement - the people who haul your dirt are as likely as not to be 10% off or so anyway (how would you know)? But you can get a good idea if you multiply the width by the length of the area you plan to turn into railroad, then multiply that by the average height (in feet) you want to raise the railroad. So a 15'x30' railroad, raised 2' on the average, will require 900 cubic feet of backfill, which (divided by 27) is about 33 cubic yards. Of course nobody says you have to get all the dirt at once. The first loop of my New Boston and Donnels Creek railroad was about 14' wide by 20' long, and averaged 18" (1.5') high, or a little over 15 cubic yards. The topsoil company I used could only bring about 9 cubic yards in one trip, but I also had dirt that I dug out from the pond, and earth from other landscaping and gardening projects to contribute, so I made it work. The northern loop of my railroad is also raised, but it's mostly raised on rock walls and timber framing, so I didn't need as much dirt there. When a business across the street had some landscaping done and the company left a pile of dirt no one wanted, I got good use of my wheelbarrow. That said, garden railroader Ray Turner had over 100 cubic yards brought in for his garden railroad, which is, admittedly, far bigger than mine.

Wall Issues

Rigidity

• Examples of rigid walls include:
  • Stone walls or concrete block walls that are held together by mortar.
  • Pressure-Treated 4x4" post and 2x6" wall combination.
  • Railroad ties that are stacked horizontally in an effective staggered pattern (like a log cabin), then fastened together and to the ground with rebar (very dry climates only).
  • Landscaping timbers that are staggered appropriately (like a log cabin) and fastened together and to the ground with rebar (very dry climates only).
  • "Castle Rock" or similar trapezoid-shaped landscaping block, the kind with the little lip to keep the upper layers from moving outward(requires good drainage).
  • "Tightly Stacked Stone" - Stacked stone that is deep and rough, so there is a lot of weight and friction to keep the stones from sliding across each other, and in which the stone pieces are properly banked, as shown below. Rough-quarried limestone works better than smooth stones like slate. Even with this solution, I may be tempted to dump a little "sand mix" in every layer to lock things in place a little better while the rest of the railroad is "settling in."
  
  
• Several kinds of walls are not rigid at all but will help to hold back dirt on hillsides (especially if you get groundcovers or vining plants established as well). They add to the natural appearance and charm of your railroad but will not help to stabilize your roadbed and track, or at least not until groundcovers establish. Popular choices include:
  • "Loosely Stacked Stone" - Miscellaneous stones that are arranged in rows or piled together so that they hold back or stabilize the soil, but not in such a way that they "interlock." This is the way my grandmothers and great-grandmothers used to make "rock gardens."
  • Stones laid with the long edge parallel to the slope of the soil, so that they hold the soil in place but only friction and inertia are holding them in place. (This only works on very shallow slopes, by the way.)

Another way to think about a wall's rigidity might be to think about how well it would hold up to your weight. The first category above should be able to hold up to you walking or climbing anywhere on its structure. You should be able to kneel on or clamber around the second category, as long as you paid attention to where you are putting your weight. But if you tried clambering around on the third category, you'd find yourself slip-sliding away. (There's nothing wrong with a wall that's not designed to hold your weight, just make certain that something else is supporting your roadbed.

Drainage

All retaining walls require pressure relief, that is, a system for allowing water to escape instead of building up pressure behind the wall, be it weep holes drilled through concrete or unmortared vertical cracks between stones in a wall.

Drainage is especially important when using wood products in your retaining wall. Timber that is made for ground contact is still not necessarily made to hold water like a bathtub. Many homeowners have discovered that landscaping projects that they expected to last the life of their home needed replaced within a few years. And we won't even talk about what that kind of upheaval does to garden railroads.

My friend Larry the contractor tells me that the best way to avoid wood products rotting out from ground contact is to keep the dirt away from them altogether. The drawing shows a hypothetical installation. A gravel buffer" lies against the lumber, with a top-quality landscaping fabric (the kind with the little tiny holes) between the dirt and the gravel. The landscaping fabric is to slow the leeching of the dirt into the gravel buffer, so that drainage is maintained. (I added the landscaping fabric on the top because I've become a weed nazi in my old age.) A side view of the same installation would show that every place the ends of the timbers (or railroad ties) appear to "butt" up against each other, there is actually an inch or two between the ends of the members, to reduce water pressure behind the wall. In the drawing, I also included gravel underneath the wall. This is suggested if you're using "landscape timbers" in a damp area - they don't really hold up as well to constant moisture as you'd think they should.

Update for 2015 - After having experienced nearly total failure of my original railroad tie installation, I no longer recommend using railroad ties or "landscape timbers" anywhere east of Kansas or in the Pacific Northwest, even if you do it the "right way." More below.

Additional points about drainage will be inserted as they relate to specific materials below.

The Wall as Transition

Most retaining walls around garden railroads use materials that won't fool anyone into thinking that they are part of the miniature world they support. However that's not altogether bad. A wall that looks like a wall provides a layer of "demarcation," a sense that here the "real world" ends and the miniature world begins. People viewing dioramas or indoor railroads don't let the base of the table distract them from enjoying the miniature world; neither will people viewing your garden railroad. As an example, the vertically-installed landscaping timber segments at the top of this page nicely separate the lawn from the railroad, while at the same time looking like they belong to both. (On the other hand, you can also tell that the protective chemicals are already leeching out of the poor things at ground level. So I would not recommend this specific installation outside of desert regions.)

One way to think about it: If you take one photo in which you can see the wall and your back yard but not the railroad, and another photo in which you can see the wall and your railroad, but not your back yard, and the wall looks like it "belongs" in both photos, you've created an effective transition.

Some garden railroaders, though, want the "borders" of the railroad to be less distinct; to make you feel a part of the railroad even as you're standing on the path. Loosely stacked stone walls achieve this effect to some extent. Some of the best examples use "cliffs" with a concrete "rock" veneer that extends right down to the ground. Ray Turner's railroad, shown to the right, is a great example.

To summarize, whether you choose a wall that draws a line between reality and imagination or one that blends the railroad into its surroundings, you'll want to choose materials that:

• Seem to fit in with the rest of the gardening and landscaping in your yard, and
• Avoid detracting from the railroad they support.

Costs

In almost every case, you need to remember that the most expensive wall is one that someone else builds. So if the most expensive solution you see also looks like the easiest, and it keeps you from spending hundreds or thousands on professional installers, that's still not a bad deal.

In the other extreme, the cheapest wall is the one made entirely of free or repurposed materials. An example would be my earliest loosely-stacked rock walls, which were made entirely from stones I found in the yard of our old house. Chances are you won't be so lucky, or you may not have time to chase down bargains. That said, you should sit down with a calculator and figure out your relative costs before you make your decision.

One way to figure out relative cost is to figure the "square foot" of surface. To give an example, a modest 15'x30' garden railroad that is raised 2' on the average will require 180 square feet of surface ([15+15+30+30]x2).

Let's say you live in the desert, in an area where termites aren't a huge problem, and you think railroad ties might do the job. (They vary in size, so be sure of what you have available before you do your final calculation.)

As an example, a railroad tie that is 8' long and 6" high gives you 4 square feet of surface. If you can get ties in good shape for $10, that gives you a base cost of $2.50 a square foot, or $450 for our example. If you figure you'll need to spend $75 on a truckload of gravel, $75 on landscaping cloth, and $20 on rebar to finish the job, your total cost for our example 15'x30'x2' railroad, would be $620, or $3.44 a square foot.

But what if ties are hard to come by in your area or you don't want to futz with anything that heavy? Most "landscaping timbers" are 8' long and 3.5" high. So each timber gives you about 2.3 square foot. If you pay $7 per timber, that's $3 a square foot. But if you want your timber walls to stay around a while, you'll want to use gravel and landscaping cloth, too. And the cost of those products could raise your total cost to something closer to $4 a square foot. So in the example shown, railroad ties would be cheaper. But if railroad ties in your area are $16@ instead of $10@, that would push the overall cost of a railroad tie wall to almost $5 a square foot, and the timbers would be the less expensive choice.

What about those cool vertical timbers as shown in the photo at the top of the page? Bad news - to stay in position, at least a third of the timber must be underground to maintain enough "leverage" to hold back the backfill. So if you want a 2' raised railroad, your timbers will need to be 3' long (longer if you're in a heavy rain area). Actually, though, these things usually come only in 8' lengths, so to maximize your investment, you'd really wind up cutting them into three 32" pieces, giving a final height of about 20". Still, the cost of the lumber will be half again as much as if you were putting these in horizontally. All other things being equal, a retaining wall for our example 15'x30'x2' railroad would cost $960 (counting crushed gravel and landscape cloth). Worse yet, in damp climates, this solution will have the shortest life span of any other solution discussed in this article; see below.

The cheapest wooden retaining wall I've stumbled across is the "fence-style" wall shown below with 2"x6"s screwed to vertical 4"x4" posts. I got the idea for this approach while doing research for my article on Accessible Garden Railroads. Many vegetable and flower gardens that have been built to serve mobility-impaired gardeners use this sort of construction. The version shown in the photos was actually a 4'x8'x1' version built for our tomato garden, which we decided to raise in 2012. The lumber for this project came to about $2 a square foot. (I got 2"x6"x12' boards for $9@ and 4"x4"x8' posts for $6@. This 4'x8'x1' raised bed used two posts and four boards, for a total of $48 of lumber to create 24 sq. ft. of retaining wall. Ironically, the pricing for this lumber was all over the map. If I had bought six 2"x6"x8' boards instead of four 2"x6"x12' boards, the cost would have been closer to $3 a square foot, so take a calculator to the store when you shop for pressure-treated lumber. Also, if I were building a higher version, I might use a higher ratio of posts, but the overall cost would still be about $3/sq.ft. For our example of a 15'x30'x2' railroad, that would come to $540. Note: In 2015, the price for most of this lumber is 25% higher than it was in 2012, so adjust your estimates accordingly.

Stones come in all shapes and sizes and cost levels; however, if you have to pay cash for your stones, a stone retaining wall will likely cost you more than any other solution. It's also hard to estimate how many square feet of retaining wall a given pile of rocks will give you. Of course, if you like the look of stone, nobody says you can't build the "front" retaining wall with stone and the back with something else, or start out with something less expensive and add stacked stone in front of it later.

Concrete products offer a good compromise, although you have to pay attention to exactly what you're getting. The most common landscaping blocks are 12" across by 4" high, so it takes three to give you a square foot of retaining wall. If you buy the kind of block that has the little molded-in "lip" in back to hold upper layers in place, and you provide a little bit of space for drainage between stones, you don't have to use crushed gravel, etc., for backfill like you should do with lumber, so your cost is mostly just the cost of the blocks. If your blocks cost you $1.75@, you'll pay $5.25 a square foot, or $945 for our example railroad. On the other hand, some discount stores are selling 8"x3" stones. Unfortunately, you need six of these to make a square foot, so if you pay $1@ for these, you're paying $6 a square foot, or $1080 for our sample wall. Worse yet, walls made with these "bargain" blocks will be less stable than walls made with the bigger ones - there is less weight and horizontal surface to create "drag," and most of them don't have the little "lips" to keep upper layers from sliding forward.

If nothing else, these examples show you that "your mileage will vary." You'll have to do your own homework on costs; we've just tried to give you some things to think about.

Wooden Retaining Walls

Railroad Ties

• Railroad ties come from real railroads, which gives them extra appeal to us train geeks.
• Their color is neutral so you can build or plant anything near them without worrying about color issues.
• Folks are so used to seeing railroad ties used in landscaping that they basically ignore them and focus on the railroads they're supporting, as opposed to some elaborate solutions that may draw attention to themselves.
• Railroad ties are so heavy that they offer exceptional stability.

On the other hand:

• Railroad ties are very heavy; most are too heavy for one person to move, even flipping them end over end as I used to do when my back was strong. So don't consider railroad ties unless you can count on the help of more than one assistant with a strong back.
• Railroad ties do not last nearly as long in most landscaping applications as they do in railroad roadbeds, where they are sitting in and on crushed stones.
• You can't always get good ties in certain areas.

Building Tips - When I was taking photos for this article, it didn't occur to me to take photos of "what not to do," but I saw plenty of examples of railroad tie walls that either looked stupid or that self-destructed because the builder had ignored basic principles.

Now that parts of my railroad are sixteen years old, I realize that - even if you use them correctly, they will not hold up indefinitely in Ohio. So I would only recommend considering them if you live someplace much dryer. If you live anywhere you have to water your lawn more than five times a year to keep it alive, you can keep reading this section, though.

One principle to consider is slope. Railroad ties (like anything with a strong horizontal line) look best when they are fairly level. If your ground is not level, consider digging it out a little so your first tier of ties lays level. (For extra protection, pour a layer of crushed gravel underneath the part that is "dug in" to give it a little extra drainage. Just because the tie has stood up to half-burial in a rocky ballast for generations doesn't mean it will stand up to full ground contact in damp topsoil indefinitely).

Another principle to consider is mechanical structure. Many folks have made the mistake of thinking that "these things are so heavy, they're not going anywhere." You would be surprised at the horizontal pressures that heavy rains, freeze-thaw cycles, or shifting soil can bring to bear on retaining walls of any kind, even railroad ties. Even my little two-tie-high "wall" bowed out more than I liked before I got out the power drill, hole saw, and rebar. The best installations stagger the ties like Lincoln Logs, then use rebar to fasten the ties to each other and to the ground. My preference would be to install each layer an inch or so "back" from the previous layer, to help compensate for an outward shift later, but you don't see that often.

A final principle to consider is drainage, as shown above. Use gravel backfill against the ties to help moisture drain away from them. Also, install the ties so that there is an inch or two gap between the ties wherever the ends come together. (On my railroad, I stuck some Creeping Jenny starts in those gaps in the hopes that it would spread out a little and soften the profile of the ties. It hasn't yet.)

Caution: As charming and useful as railroad ties are in the garden, Ohio State warns that they most likely contain chemicals that make them unsuitable for use in a garden in which food is going to be grown. Now, that's not likely to affect many garden railroaders, but we thought you should know.

Landscaping Timbers

Timber buried completely in the soil may not receive enough oxygen to support decay, and timber above the soil generally doesn't stay moist enough to support decay. But un-treated, or under-treated timber at the soil line in moist climates creates a "perfect storm" for premature decay. That's why I show the gravel underneath the landscaping timbers in the discussion on drainage. Yes, using a gravel "footing" instead of hard-packed dirt may be more hassle at first, but if it keeps you from tearing things out every 7 years or so, it's worth it, don't you think? Also, it's a lot easier to replace these before they blow apart, spilling mud and trains on the adjacent walkway.

Building Tips - As discussed above, these work best when they're stacked in a "log cabin" formation with the lengths interlocked, then fastened together with spikes or rebar (preferred for anything over three layers high). For the best visual effect, try to keep the horizontal posts level, rather than having them go up and down with the slope of your yard. And monitor them seasonally for any signs of premature decay that might indicate it's time to improve drainage or make other changes.

What about vertically-mounted Landscaping Timbers? - As you can suppose from what was written above, landscaping timbers do not have enough treatment to withstand full ground contact indefinitely, and worse yet, are especially vulnerable where the post enters the ground. Although I admire the vertical timber walls I've seen, I can't help noticing how soon the greenish "treatment" color fades away near the ground, or how often folks have to start shoring them up somehow after a few years. In other words, this is an attractive, but not necessarily a permanent solution.

Update for 2015 - Since I last edited the paragraph above, my angry-at-the-world neighbor threw up a privacy fence on both sides of his property, using the cheapest possible panels and those 3.5"x6"x8' landscaping timbers instead of fence posts. If he'd told me he was going to do it, I'd have split the cost with him and bought decent materials. As it was, the landscaping timbers were only about $2 cheaper than 4"x4"x8' ground-contact-rated posts, so he saved about $16 by buying them. Our water table is so high that sometimes in the spring, that part of the yard is standing in water for weeks. Plus we get high winds from the west.

You guessed it, within fifteen months, several panels of the cheapo fence was laying on the Arborvitaes I had planted near the fenceline to hide his trash piles (did I mention he was a great neighbor). The landscaping timbers had rotted out and snapped off. I went to the store and bought several 4"x4"x8' posts and installed them on my side of the propertly line adjacent to his rotted and rotting posts. I also connected my posts with 2x6s to dress up my side of the thing. From my side it looks great. And if the cheapo fence ever falls apart completely and the people who live there now want to keep a privacy fence there, it will be a "piece of cake" to screw good panels onto the posts.

Consider using 4x4s Instead - It occurs to me that if you want the sort of "log cabin" retaining wall that folks often buy the cheapo landscaping materials to create, the cost of ground-rated 4"x4"x8' posts would only be 25-30% more, and they would last much, much longer. Plus, since they no longer use arsenic to bug-proof the things, they're much safer to have around than they used to be.

That said there is an even cheaper solution that is just as attractive. Read on.

Fence-style Construction

Building Tips - I used 2"x6"s because for some unknown reason, 2"x6"x12' pieces cost substantially less per "square foot" than 2'"x8"s or 2"x10"s, or even 2"x6"x8' pieces, which would have worked just as well.

Because I was creating three of these in a row to create my new "vegetable garden," I was more careful about measurements on these than I usually am on measuring the boundaries for my railroad. I measured the location of each post carefully, then dug the posthole to just below the frost line (I didn't use concrete because this is in a garden someone might want to reuse as a regular garden some time).

Then I cut the posts and set them loosely in each hole. Next I used two of the 2"x6"s to build a framework that looked like a bottomless 4'x8' box. I set the box over the first set of posts and used a square and tape measure to make certain that the box was parallel to the garage and perfectly rectangular. Then I backfilled the post holes enough to hold the posts in place and checked again. When I was certain I had the right location for each post, I tamped the dirt in around them. Then, using a level, I found the highest corner of my "box." I screwed the box to the post there, then continuing to use the level, raised the framework the right amount all the way around and screwed it to the remaining posts. Because the ground sloped, there was a few inches' worth of space between the box and the ground at one end. After checking the "square" all the way around, I added the next layer of 2"x6"s, then added a few more screws to both levels to keep the whole thing very solid.

As it turned out, all of the posts stuck out a little, and some of them stuck way out. I trimmed the long posts to match to match the short ones, but left them there in case I want to add another layer's worth of height some day. If I was doing it for my railroad, I would trim the posts flat. At any rate, I them backfilled now and holding tomatoes, cucumbers, and zucchinis. (It would be more fun to have them holding trains, but I have another garden for that.) As of this writing, several years have gone by without any noticeable problems. I've added two more raised gardens, and I've even used this technique to shore part of my railroad where the ties completely gave out.

Stone Retaining Walls

If you don't have free access to good limestone blocks, though, you'll either have to come up with serious cash or make do with odds and ends (most of which are fairly round north of I-70).

Loosely Stacked Stone

Building Tips - Although there is some engineering to any stacked stone wall (see below), there is more "art" than "craft" in arranging irregular "found" stones on a slope. In my case, I made certain that there was topsoil between the layers, and I poked starts of miniature sedums (mostly Acre and Stubby Fingers) into the cracks between the stones once they were installed, to give the look of vegetation taking root in a cliffside. If I had to build my railroad over again, I'd still use loosely stacked stone on the "front," I'd just give my roadbed a firmer foundation and not count on a stacked stone wall to hold everything exactly in place.

Tightly Stacked Stone

Building Tips - Treat flat stone like any other stone; install it at a slight angle, backfill carefully, and make certain that each layer is reasonably stable before you add the next layer. The nearly vertical "flat stone" wall in the photo is actually not holding dirt as much as it is hiding the pump and filter mechanism for the owner's waterfall. It's also on a portion of the railroad where no one would be climbing. Again, if this was a "real" retaining wall, I'd recommend a little more angle to it.

Building a Stacked Stone Wall

To start, make certain your lowest row of stones is firmly set into the soil. If your stones are somewhat flat, they should lean back "into" the slope as shown in the photo. Commercially quarried "flat rocks" don't have to lean back as steeply as the irregular stones shown in the drawing, but there should still be a pitch of about 5 degrees.

Backfill to the top of the first row of stones, filling any gaps between the stones. Tamp down the backfill firmly enough that it can support the "back" of the next row of stones.

Add a layer at a time, backfilling and tamping between each layer. Be certain to fill gaps between the stones with soil as well. (Later you can go back and stick sedum starts in each gap to give the wall and to help stabilize the soil). If your rocks are entirely irregular, you may find yourself resting the next layer on the tamped-down dirt behind the lower layer instead of resting it even partially on the stones. This isn't a problem, but it will make your slope far more gradual.

Concrete Product Retaining Walls

Landscaping Blocks

But when easy to use "mortarless" products began to be made for do-it-yourselfers with deep pockets, visions of "castle walls" began to spread across the land. The most common version is shaped something like a bulging trapezoid with the sharpest corners knocked off. In fact, on many of these blocks the corners are knocked off, literally, to give the blocks' face a more natural appearance.

Building Tips Instructions for building a mortared wall are beyond the scope of this article (and there are already many books on the subject at your library). So the following notes focus on the kinds of "mortarless" systems used by most do-it-your-selfers, including garden railroaders. When you shop for landscaping blocks, look for heavy blocks with a little "lip" on the back of each block to keep upper layers from sliding forward over lower layers. You'll also have to figure what the "pitch" of a wall made with these blocks will be, so you can start the lowest layer far enough "out" to compensate for each layer receding a half-inch or so back from the layer below it. Also:

• Consider how you will finish the top layer. Since you're using this system to provide a base for something that demands close inspection (your railroad), consider how the top of the wall will look when you're done. Some mortarless systems come with "capstones" to dress up the top layer. Or you may consider some solution to camouflage the top layer, such as installing scenery or roadbed near the edge, over the top of the block. Or you may be fine with the way they look period, which is also your choice. The point is to think about it.
• Make the base layer as horizontal as possible, even if it means digging some blocks into a sort of trench. Your wall's "footprint" can be as round or as straight as you want it. But if your blocks look like they're going up one hill and down the next, you spoil the effect.
• Make certain that the base blocks are level from front-to-back. This means that if you're using the blocks with "lips" on a hard, flat surface like a concrete driveway, you'll have to:
  • Buy matching "capstones" without the lips and use that for your base layer, or
  • Whack the lips off with a big hammer before you install the base layer (wear safety goggles), or
  • Carve a trench to accommodate the lips of the base layer.
• Leave a little horizontal "breathing space" between stones to provide drainage.

Even after you're satisfied with your "final" installation, inspect it every few weeks at first (and every few months thereafter) for signs of bulging or settling that will detract from the cosmetic or mechanical benefits of the wall. And don't let kids walk around the top edge (they will try, especially if it looks like a row of stepping-stones).

Poured Concrete Walls

Cosmetic Treatments for Retaining Walls

A Wall Over a Wall

Concrete Cliff Veneer

Another approach that is available even to people who don't have a back yard full of old building foundations is to use a homemade concrete stone "veneer". Since Bob Treat documented this method for Garden Railways in the August/September, 2001 issue, many other modelers have adopted his technique, including Ray Turner, whose work is discussed in the Transition section.

One advantage of this method is that you can use inexpensive methods such as concrete blocks or a pressure-treated lumber "fence" to get your railroad started, then go back later and dress it up. The end result is dramatic, and you've still spent less than you would if you had gone with "castle rocks" or something.

Scale Model Walls

Another approach is to build "cribbing" from scale-sized timbers. This is a kind of retaining wall in which timbers poke back into the earth to stabilize the whole structure. Again, a little bit of effort can provide a great deal of interest. Some examples of cribbing I've seen on model and garden railroads are only a veneer that looks like cribbing. This one looks like the builders have actually built a functional example.

Again, these are only examples of ways you can dress up retaining walls - there are almost as many solutions are there are garden railroaders.

Conclusion

Since I've been looking at home-made (and even some commercial) retaining walls on purpose for the last few months, I've noticed enough examples of "what not to do" to fill a book. If you're wondering why I have so many cautions and "gotcha's" above, the answer is that short cuts don't work.

Okay, that's enough scarey stuff. The truth is that building an effective, attractive retaining wall to support your plants and villages (and if necessary, your trains) is within the reach of every homeowner, if you just take the time to follow some simple guidelines.

If you have any images of your railroad construction that you'd like to share or any tips or other things I've left out, please get in contact, and I'll publish whatever you have.

Best of luck,

Paul D. Race, Editor for Family Garden Trains

Reader Feedback and Tips

Dave Smith, of Long Island:

Great article on retaining walls and backfill! Subjects near and dear to my heart since my layout is raised. I have no changes with what you wrote but might have some additions readers might find helpful (based on mistakes I made).

When ordering "fill" there is a difference in what you can get, at least here on Long Island. Clean fill is cheaper than top soil or sand/gravel but you'll get bits of glass and other small "junk" in it. This in itself is not too bad but when I got my first load of fill it was damp and HEAVY! If you're moving it yourself via wheelbarrow, be sure what you're getting is as dry as it can be.

When filling in the planter DON'T fill in with old tires, old auto rims or harden bags of old cement. Believe me when I tell you, wherever you put those items is going to be the EXACT spot you're going to have to dig someday. [I'll add that old tires will rise through the earth to the surface like something from a CSI episode after a few freeze-thaw cycles. - Paul]

Someone may think that it might be wise to rent a soil compactor to get the fill inside the retaining wall "packed" down. I was told by a rental place that if you use a powered compactor you'll probably never get anything to drain or grow because the machine does its job so well. I did my moving of dirt in the fall and let the winter snow and rains "settle it in".

When building a raised bed along a fence for mercy sakes leave at lest 18" between the wall and the fence (24" is better) You'll thank me when you need to work on the fence side of the layout in order to maintain track, shore up a sagging retaining wall OR replace the fence!

If building a wall out of nominal sized lumber, say 2x10x8, and using vertical posts to support the boards, put the vertical supports on 4 foot centers. I tried to support them on 8 foot centers and the boards bowed out in the middle from the weight of the fill. I also placed plastic sheeting on the inside of the boards where the soil would contact them. Besides getting torn when shoveling in dirt, the plastic seemed to hold MORE moisture against the wood and sped up rot.

Remember when using "real" railroad ties that have been treated with creosote, sometimes, in very hot weather, the creosote will STILL ooze out and ruin the clothing of anyone brushing up against it.

Consider a walkway around the retaining wall. Unlike a ground level railroad where people don't seem to "follow a distinct path" around the layout, it appears to me that when you make boundaries using a retaining wall, everyone walks right along the wall and the grass quickly becomes only dirt (even a layer of gravel will help here).

When working with pressure treated wood, consider using sizes that aren't "square" (i.e.6x6). I'm using a pressure treated timber that is 4 by 6. This make the total weight less and easier to cut. Also, consider using the timber screws sold at the major home outlets rather than nails or rebar to hold things together. They're more expensive but when you realize you made a mistake, and you will, it is so much easier just to unscrew a timber screw than try and pull a timber nail/spike out of the wood. They also do less damage to the wood and I believe hold things together better.

[In another part of his response, Dave had made a reference to "sleepers" that I asked him to clarify. His response is below:]

When building a long retaining wall of multiple timbers, every once in a while you're supposed to turn a timber perpendicular to the main wall. This timber, fastened to the lower timber and perhaps even fastened to the two timbers on either side, stabilizes the wall and prevents it from moving outwards. The photo in your article titled, "Interlocked RR ties fastened with rebar..." shows the idea of a sleeper. In that photo, consider that, instead of the wall ending, it continued along. The second railroad tie that makes up the end wall in the current photo would be installed as a "sleeper". That is, in the exact same place and direction it is now in but without the top and bottom timbers show as the end wall in the photo. The other railroad ties surrounding it would be fastened to it. In that configuration, most of the second RR tie would be back in the dirt of the planter and offer stability to the outer wall timbers.

Dick Friedman, of California:

Ray Turner, of Silicon Valley, California:

At least in California with its heavy clay soils we get a lot of settling. So for starters, build the wall on compacted soil. If you have to dig a little where you're going to build a wall (like for electrical and plumbing pipes or to create a level base), pound it tight before placing the wall, or use sand to backfill a hole since it won't compact later. I built a lot of walls with stacking blocks and I would say to spend a lot of time getting the bottom row level and even. This is time well spent as the upper rows will go on so much easier and be more stable. Also, fill and compact the spaces between the blocks on each layer before adding the next layer of blocks. This will avoid dirt settling later and lowering your railroad. For sloped ground, it's easier to start at the low point and work toward higher ground.

I understand Dave Smith's advice about having to dig later in VERY compacted soil, but I had the opposite problem of just hosing down the area and walking on it to compact it. For the next two years the railroad settled and I had to keep re-leveling the track and re-ballasting it. Who's got the patience to let the ground settle for 1-2 years before building your railroad?

I echo Dave Smith's comment about Creosote staining clothes. Also, Creosote is pretty toxic so wear a mask if you're going to be cutting it with power tools. I found that a chain saw was dulled in no time from the creosote and sand on the tie. I used a carbide blade in my circular saw to cut a ring around the tie and then cut through the center with a bow saw - much less work than manually cutting all the way through.

Also, I would draw one more contrast between RR tie walls and stone/block walls. Stone/block walls can be irregularly shaped which allows a more organic shape for your yard and RR that the straight sides afforded by RR ties don't.

Great work Paul. Keep it up.

Wil Davis, of Dayton, Ohio:

Peter Stremic, greater Philly:

Only thing I have any comments on is the section on using RR ties.

I installed a ton of these back when I was still able to, about 20 years. I used in general landscaping applications though, not RR areas. I'm replacing them now with jumbo Belgian blocks. I also put some of them a tad too close to the house and invited a few termite colonies by doing so.

They've all but turned to rot now, so you may want to give a "caveat emptor" about using these. Real RR ties will also wreak havoc on the users chain saws... better get ready to replace these several times, depending on the number of cuts.

Also, I didn't see anything regarding offsetting these, or 6x6 PT timbers either, by 1/2" to 1", depending on the number of courses. If the people stack these without any offset, the resulting wall will look like it's tilting away from the bordered area, when actually it may be perfectly perpendicular to the ground. It's an optical illustion thing, but it's still unsightly IMHO.

Nice job! and thanks for sharing.

Walter Sheldon

Early versions that did not use multiple rods, began to bulge, but drilling a hole and running a new rod thru to the opposite side I was able to pull the sides back together. This time you will have to add a nut and washer on the outside to pull the sides in.

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