How to Build a Stacked and Mortared Limestone Wall
If you’re looking to incorporate groovy limestone features like planters, retaining walls, and waterfalls in your garden’s design, the operative word is “wall.” You’re going to need at least one if you want structures like these in your garden. And if you’re up for tackling your limestone garden project yourself, you’re in the right place. Keep it here to learn how to build a stacked and mortared limestone wall.
Table of Contents
Introduction
Greetings, gang, and welcome back. Today’s offering takes us into the heart of The Renaissance Garden Guy “Garden Construction and Hardscape” category. In past articles here, I’ve discussed my use of limestone in my garden’s design. The article titled “My Garden Design Scheme” lays out all of my existing, planned, and ongoing limestone-garden-feature-building-and-implementation activities. Overall, these activities make for a pretty ambitious project; but what’s already been built looks pretty cool, and what’s coming up should be even cooler. The plan incorporates a lot of limestone planters of varying heights (I built the first section in 2020), and a fairly substantial waterfall and much larger (than the existing) pond. There are limestone walking paths in the plan, as well, but you’ll read about how I build those in a future article. The point today is that the construction of limestone planters and waterfalls relies on the implementation of one major component: the wall. So today, I’m going to show you how to build a stacked and mortared limestone wall. We’ll start with a quick look at the benefits and drawbacks of both a dry stacked limestone wall and a stacked and mortared limestone wall, and then I’ll get right into the nuts and bolts – or stones and mortar – of how to build your own stacked and mortared limestone wall.
Dry Stacked or Stacked and Mortared Limestone Wall: Which is Better?
Before you ask how to build a stacked and mortared limestone wall, you need to make sure that it’s the limestone wall that you really want. It’s not the only kind. A limestone wall can be built as a dry stacked or stacked and mortared wall. A dry stacked wall is exactly what it sounds like: a wall built of stones stacked on top of one another, with no bonding agent – such as mortar – affixing them to one another. The weight of the stones holds them in place and the result is a wall that can be easily dismantled or restructured because its components – the individual stones – are loosely placed. A stacked and mortared wall, on the other hand, is solid and totally immovable. The individual stones are mortared to a stable concrete footing, and stacked with mortar holding each one of them permanently in place. If a stacked and mortared stone wall is engineered and built correctly, it’ll be standing until doomsday.
Benefits of a Dry Stacked Limestone Wall
- Drainage. When used to construct a planter, the dry stacking methodology offers beneficial drainage. Excess water readily drains out of the planter through the gaps between the stacked stones.
- No footing required. A dry stacked wall can be laid out directly on surface of the ground without the need for a solid, immovable concrete footing. If the substrate is loam or clay, which is prone to heaving during freezing temperatures, the loosely set stones of the wall will shift with the expanding and contracting ground. A modest amount of ground movement should not compromise the integrity of a dry stacked wall. If the substrate is sand, which does not heave or contract with freezing/thawing temperatures, the situation is even better. The dry stacked wall won’t move at all, even though its loosely laid construction does safely permit some movement.
- Appearance. It’s often easy to achieve a natural, or “relaxed” look for a dry stacked wall because there are no visible signs of affixation. In other words, there are no mortar joints – just stones piled on top of one another. Although such a wall is obviously engineered, it doesn’t look too terribly so.
- Reworkability. Just like it sounds. Since its individual units are loosely placed and not permanently affixed to anything, a dry stacked limestone wall can be easily reworked and/or restructured.
Drawbacks of a Dry Stacked Limestone Wall
- Motility. The ability of a dry stacked wall to shift and move can work against it in certain circumstances. If the underlying ground is subject to extensive and dramatic heaving, a dry stacked wall could possibly topple. Even routine movements like dragging a water hose across the top course of a dry stacked wall can dislodge individual stones and send them tumbling to the ground. The toads and frogs which live in my garden are usually around when I’m watering. It wouldn’t do to knock pieces of limestone off the top of a wall when those little guys are close by.
- Soil leakage. Since there are gaps of varying size between the individual stones of a dry stacked limestone wall, soil can leech its way out from a planter built in this way – particularly when that soil becomes drenched through natural precipitation or watering. Trust me. It happens.
- Unsuitable as a base for additional structures. A dry stacked wall will not provide a stable base for continuing/attached structures, particularly if those structures are designed to be higher than that particular dry stacked wall, or designed to rely on the dry stacked wall as a basis of structural support and stability. If the wall moves, anything attached to it, or built on top of it, will also move.
Note: Depending on the size of the individual stones being used in a dry stacked limestone wall, that wall’s stability can range from poor to pretty good. A wall built with small and light stones dry stacked atop one another will not be as stable as one that’s dry stacked with big, heavy stones. (In either case, a dry stacked wall will never be as stable as a stacked and mortared wall.) Likewise, the reworkability of a dry stacked wall will be directly affected by the size of the individual stones – small units are obviously much easier to move around than stones that are big and heavy.
Benefits of a Stacked and Mortared Limestone Wall
- Stability, strength, and permanence. Just like it sounds. A correctly engineered and constructed stacked and mortared limestone wall is totally stable, incredibly strong, and definitely permanent. It lends itself well as a base for continuing/additional structures and will withstand any and all ground heaving/movement and will never be affected by someone or something bumping into it.
- Drainage. My stacked and mortared limestone planter drains beautifully. As long as the planter’s interior has an open floor (just the earth as a floor), and the substrate is not dense clay, the planter will drain beautifully. If the substrate is clay, you may want to consider digging down another 12″ to 18″ and replacing the clay you’ve dug out with sand or 3/4″ crushed stone, and then filling the planter with a high quality soil.
- Appearance. The effect is up to you. You can “stuff” the joints between stones with mortar so that the mortar joint is really evident and obvious, or you can recess the mortar joint back from the face of the wall so the stones look almost like they’re dry stacked. A stacked and mortared wall can be just as beautiful and “natural” looking as a dry stacked wall.
- No soil leakage. Since the joints between individual stones are mortared, there is no possibility of soil escaping from within a planter built with a stacked and mortared wall system.
Drawbacks of a Stacked and Mortared Limestone Wall
- Need for a concrete footing. There’s no way around this one. If you’re going to build a structurally sound stacked and mortared limestone wall, it’s going to need an appropriate concrete footing. The footing negates any and all movement of the ground and provides the absolutely necessary level and stable surface upon which to build the wall. A stacked and mortared wall built with no footing, or an inadequate footing, will soon suffer cracks and instability as the ground beneath it shifts and stresses – and ultimately cracks – the wall’s mortar joints. If you want a wall like this, and you want it to last, you’ve gotta dig and you’ve gotta pour some concrete.
- Extremely poor to impossible reworkability. You can’t just pick up the stones and move them around when they’re all mortared in place. What’s done is done. Unless demolition is in your plans.
How to Build a Stacked and Mortared Limestone Wall: The 10-Step Template
I’d be lying to you if I told you that building these kinds of things is a piece of cake. It’s not. There’s a lot of work that goes into building a structure comprised of stacked and mortared limestone walls. But if you plan that structure properly, and think everything through ahead of time, it’ll make your building project run smoothly without a lot of unnecessary screwing around. Here’s the template I use for my own limestone building projects. Follow it, and you’ll have an excellent plan and have a damned good idea of how to build your own stacked and mortared limestone wall. I break my game plan down into the following steps:
1. Observe, Anticipate, and Measure
2.Locate Utilities
3. Design and Plan
4. Follow All Local Ordinances and Obtain All Necessary Permitting
5. Get Your Materials Together
6. Get Your Tools Together
7. Run All Planned Power and/or Water
8. Dig, Form, and Pour Your Footing
9. Lay Your Limestone
10. Use Concrete Blocks (CMUs -Concrete Masonry Units) When Possible in Non-visible Locations
1. Observe, Anticipate, and Measure
This is the all-important first step that you’ll be taking when you decide to build a stacked and mortared limestone wall. The characteristics of your land, specifically, the intended location of your planned limestone structure(s) and the amount of space you’ll have to work with, are your project’s starting points. Take a serious look around and understand these things. Then, anticipate. Anticipate your limestone structure’s use. Is it going to be a planter? A retaining wall? A cascading waterfall? If you want to build a limestone planter in your garden, what will be growing in it? Will those plants need lots of sun? Or shade? Observing your structure’s potential location, assessing space considerations and other determining conditions, and accurately and correctly anticipating the structure’s suitability for the spot(s) you’ve got in mind are your initial imperatives.
Once you’ve gotten your mind around these things, take some measurements. The best way to understand the proper dimensioning for your structure is to get outside and measure. Measure the total space available to you, then measure the length, width (depth) and height of the thing you’re planning to build, and make sure the numbers work well together. This step will give you a feel for the actual size of your structure, and how much room it will end up occupying and will often inject a dose of reality into your planning. My pie-in-the sky ideas of mountainous limestone structures were quickly modified to incorporate much more modest dimensioning once I actually measured how much room I actually had to work with. You should record the measurements you take. You’ll use these as the starting point for the drawing(s) you’ll make in Step 3.
In terms of observing your structure’s location, I’ll make a really strong suggestion. Make sure you understand what your land’s substrate is made of. Is it loam? Clay? Sand? The underlying composition of your land will determine, among other things, the required depth of the concrete footing you’ll pour in Step 8, and either your ability to build over, or entirely change your intended spot in order to avoid buried utilities, which you’ll locate in the next step.
2. Locate Utilities
Knowing how to build a stacked and mortared limestone wall means first knowing where all underground utilities are buried. So, I’ll say this again: Before you do any digging for a garden construction project, locate any and all utilities. This is critical. You’ve got to know if and where gas, electric, cable, telephone, and/or water lines are buried – and if possible, how deep they’re buried – before you start excavating. Contact a local utility locating company and have them send out personnel to locate your lines. Once they do, they may be able to give you an idea of the depth at which they’re buried. If the lines run below the ground where you’re planning to build your structure, pick another location. Simple. There’s no practical reason to try to build a concrete and limestone permanent structure over utility lines. Aside from the risk you’ll run of striking a line when you’re digging, any potential repair/replacement of an existing utility line will necessitate the need for excavation, and the inevitable demolition and removal of your structure. Build it somewhere else.
3. Design and Plan
In my article of January 2022 about the massive arbor and trellis structure I built in my garden in the fall of 2021, I discussed at great length the absolute necessity for a plan and a set of working drawings. This necessity holds true for any construction project you may be planning, including your limestone structure project.
There are countless numbers of designs and drawing sets available in books and online as downloads. And, of course, you can come up with your own design and drawings. In fact, it can definitely be more beneficial for you to use your own plan. After all, back in Step 1, you got to know the characteristics and space limitations of your intended construction site intimately. Who better to come up with a plan for some wildly cool limestone structure for your own property than you?
If you’re planning on using your own design, your drawing does not need to be of Frank Lloyd Wright quality, and it doesn’t need to have structural engineering detail. It should include dimensions (overall, and for individual elements), elevations (heights and below-grade depths), and a rough sketch, or sketches, of how you want things to look when everything is done. You’ll thank yourself when you’re in mid-construction and you get hung up on something, or you forget how tall something’s supposed to be, and you can refer to the handy-dandy drawings you’ve created that will jog your memory and remind you precisely of how to build your stacked and mortared limestone wall(s).
Trust me. Make yourself a set of drawings.
4. Follow All Local Ordinances and Obtain All Necessary Permitting
Check with your municipality or county’s building department regarding permitting requirements, building code requirements, and/or ordinances. Chances are, you’ll get a bunch of useful project information (like frost line depths) along the way.
5. Get Your Materials Together
There’s nothing worse than running out of materials when you’re right in the middle of a construction project. Make sure you’ve got everything you need ahead of time. The drawings that you intelligently created back in Step 3 will be your guide for the required materials and their respective quantities. Your drawings will jog your memory in case you’ve forgotten about easily overlooked items like the forms you’ll need to pour the concrete for your footings, or the pipe material you’ll need to implement a “chase” to run plumbing or electricity directly through those concrete footings (more on footings and chases in just a bit). Refer to your drawings, and the measurements you’ve taken and recorded there, then make a materials list and get all your stuff. Knowing how to build a stacked and mortared limestone wall the right way means having all of your munitions stockpiled and good to go. Over-buy when you can – it’s better to have too much than not enough. Except for a few different types of material, you can always return the excesses.
How Much Limestone Will I Need to Build a Stacked and Mortared Limestone Wall?
Good question. The amount you’ll need is probably somewhat variable, and contingent, at least to some degree, on the size of the stones you’ll use, and how large you’ll make your mortar joints. I can give you a very basic rule of thumb based on my completed first planter section. I used individual stones that fall into the “landscape stone” size as offered by most stone retailers/wholesalers. Although there are a few curves and a second, higher tier to the wall that comprises this planter, my measurements tell me that it is approximately 19 linear feet (or 228 inches in overall length) by approximately 20 inches in height. My horizontal mortar joints average between 3/4″ and 1-3/4″ in thickness, and the vertical mortar joints vary from 1/4″ to 1-1/2″ in width (this variance in the size of the horizontal and vertical mortar joints is due to the irregularity in size and thickness of the individual stones). I used approximately one ton, or 2,000 pounds of limestone “landscape stones” to build my planter. So, a stacked and mortared limestone wall, as I’ve built mine – including the mortar joints as I’ve implemented them – at a height of 20 inches, will use approximately 105-106 pounds of limestone per linear foot (2,000 lbs ÷ 19 feet). You can take these numbers and extrapolate to come up with a value for your own wall. If your wall is only going to be 10 inches tall (1/2 of 20 inches), you’ll need only around 53 pounds per linear foot (106 lbs ÷ 2). If your wall is going to be 30 inches tall (1.5 x the height of my 20″ tall wall), you’ll need somewhere around 160 pounds per linear foot (106 lbs x 1.5).
I want to emphasize again that this is just a rough rule of thumb. It’s based entirely on my own set of design and construction circumstances, and the figures are approximate. At the very least, it will provide you with a ballpark figure to keep in mind when it’s time to go shopping for limestone.
6. Get Your Tools Together
This step can include wide variations in terms of the types of tools you’ll be using. If you’re running electricty or plumbing (as in tubing for a pond/waterfall pump), you’ll need specific tools designed for that type of work. But let’s say that you’re just going to be building a stacked and mortared limestone wall, set upon a concrete footing, just like it’s supposed to be. The following is a basic lineup:
- Tape measure
- Claw hammer
- Brick hammer
- Wheelbarrow
- Mixing box/trough
- Mortar hoe
- Round point shovel
- Flat shovel
- String line
- String level
- Box level
- 24″ masonry level
- Masonry hawk
- Masonry/brick trowel (different sizes)
- Pointing iron (different sizes)
- Brick jointing tool (different sizes)
- Concrete float
- Cordless driver/drill
- Worm drive saw or circular saw (for cutting wood/plastic forms and staking material)
- Paint tray and paint brush (for applying form oil)
This aluminum masonry hawk from Edward Tools is strong, light, and maneuverable. Use it to keep a workable pile of mortar right in front of you while you lay and point your stones. It’s the one I use for all of my masonry projects. If you want to build a stacked and mortared limestone wall, this tool is absolutely indispensable. Click the #advertisement link to order it here, conveniently, direct from Amazon.
I love Marshalltown’s line of masonry trowels. I’ve got several in two different sizes. Order them here, directly from Amazon, by clicking the #advertisement link.
I use Marshalltown pointing irons for getting mortar into tight spaces between stones. I’ve got them in 7/8″, 3/4″, 1/2″ and 3/8″ sizes. Build a stacked and mortared limestone wall the right way by using the right pointing irons. Critical point here, gang. Click the #advertisement link to order them directly and conveniently from Amazon.
I’ve got Marshalltown brick jointing tools in 3/4″/7/8″ and 3/8″/1/2″ combo sizes. Use them to create, smooth out, and shape recessed mortar joints. I’ve used them for years. Order them here, conveniently and directly from Amazon, by clicking the #advertisement link.
7. Run All Planned Power and/or Water
If you’re going to have, for example, a water feature with non-freezing water in it during the freezing winter months, there’s going to be a heater, and electricity, involved. And if you’ve got the cascading flow of a waterfall in mind for that water feature, then there’s going to be a pump, and electricity PLUS plumbing, involved. And if those heated and cascading waters are going to be doing their thing amidst the structural elements of your planned stacked and mortared limestone walls, you’re going to need a way to get everything connected – or at least have the pathways for those connections in place – before you finish building those walls.
Trying to explain this particular Step 7 subject can get really complicated, so I’ll try to keep it as simple as possible. For my structures, I’ve chosen to route the direct line voltage electrical power under my planters along the western elevation of my garden southward, toward the locations of my planned waterfall and expanded pond (complete with a large pump, heater, and waterfall spillway box). I ran rigid, heavy-wall steel conduit (through which I’ll pull the electrical wires) belowground at a greater depth than any concrete footings. This was part of my plan. I ran this pipe before I began any work on my existing limestone walls and their footings. It will terminate in a location where my new waterfall pump and heater can easily plug in. This has been the relatively easy part – to implement and to explain. The slightly more complicated part will come when I run the pump hose from my pond’s skimmer box/pump location up through my planned high planter/top waterfall tier location to the waterfall spillway, and when I run the pump’s power cord to the power source. I’m not planning to trench deep into the ground below my planned footing depth (as I did with the steel conduit running beneath my first planter section, as described above) to run my pump’s water hose and electrical cord, so they’ll each need to pass, below grade, through the concrete footings I’ll be pouring on which my limestone walls will be built. I’ll need to install a chase for each – the pump’s water hose, as well as its electrical cord – through the planned concrete footings.
In the case of a project like this, a chase is an opening in a solid structure (the concrete footing) through which electrical, plumbing, mechanical, gas, cable, and/or telephone lines pass. When I work on my concrete footings (which you’ll read about next), I’ll make sure to have two sections of PVC pipe in place – each with a diameter large enough to easily pass the pump hose and power cord through, respectively. These chase pipes will be routed through the footing forms (and through the concrete in which they’ll be encased), underground, and up through the soil so that they’ll deliver the pump hose to its point of attachment to the waterfall spillway, and the pump’s power cord to the waiting electrical receptacle.
There are two takeaways here: 1) When you’re planning how to build your stacked and mortared limestone walls, make sure you anticipate the need for any electrical and plumbing lines, and that you incorporate their routing in your drawings. 2) You’re more than likely going to need to incorporate one or more chases (chase pipes) in your plans, each with a diameter large enough to accommodate and deliver these lines to their intended locations.
Hint: When running chase pipe material, make sure that any changes in direction – from side to side, or up and down – are accomplished gradually. You’ll need to be pulling things like electrical cords/plugs, or flexible water hose through them. Use 45° elbow fittings or “sweep” (longer radius) 90° elbow fittings. It would be a real bitch to get this far and not be able to pull your lines through the chases you’ve installed.
API Pond Algaefix. Knowing how to build a stacked and mortared limestone wall, and associated structures, in your own garden means knowing how to maintain them after they’re built. If you’re planning to have a water feature to go along with all your groovy new limestone, then plan on having some intense algae, too. API Pond Algaefix is the product I use to control and eliminate unwanted algae growth in my gardens’ water features. This product very effectively controls and/or eliminates green or green water algae (Chlorella), string or hair algae (Cladophora), and blanketweed (Oedogonium) in my two ornamental ponds. The product comes with very exacting manufacturer’s directions, which in turn must be followed exactly. When used according to these manufacturer’s directions, API Pond Algaefix is harmless to fish and aquatic amphibians and reptiles. My large frog and toad populations have never been harmed by this product. It keeps my ponds extremely clear and free of unsightly and unwanted algae growth, and is simple to administer. I highly recommend this product. I’ll stress again, however, that all manufacturer’s directions must be followed exactly. To learn more about this excellent product, or to order it here, directly from Amazon, please click the #advertisement link.
8. Dig, Form, and Pour Your Footing
A footing is an integral and absolutely necessary element for anything that’s built outdoors as a permanent structure. In the case of building stacked and mortared limestone walls, footings are made of poured, high-strength (or mechanically reinforced) concrete. The footing provides a perfectly level and stable surface upon which to build the walls. In cold areas, and where the ground is subject to heaving and contraction, footings are often poured to a depth slightly exceeding the local frost line. Frozen ground heaving is caused by the freezing and expansion of groundwater trapped in the soil. Unlike soil or clay, sand does not retain water, so it does not heave in freezing temperatures. If the substrate (the ground just below the surface) of a particular land is sand, any concrete footings poured there do not need to be terribly deep. The substrate of my property is sand. Although I’d excavated much of the land that my garden occupies and replaced as much as the top four feet of sand with soil in a number of locations (back in the spring/summer of 2020), I knew, at that time, that I’d eventually be building limestone walls along the southern and western borders of my garden, so I left the sand in these locations undisturbed. I knew that I’d be pouring footings, and I knew that if I was pouring them into a sand substrate, they wouldn’t need to be super deep. Leaving the sand in the ground in the areas of my eventual stacked and mortared limestone walls was one of my smarter moves as a so-called gardener/garden designer/garden builder.
Note: I’m going to tell you again right here how important it is to have your utility lines professionally located and marked, to obtain any and all required permitting, and to consult your local building codes to determine the depth of your frost line. Make your project safe, legal, and structurally sound.
- Dig. Dig the trench for your footing according to the drawing you made back in Step 3. It should be wide enough so that your finished footing extends about an inch on each side beyond the width of the widest stone you’ll be laying on it. And it should be deep enough so that it extends to just below your specific frost line depth. In my non-heaving sand, my footings are 18″ deep.
- Form. You’ll need to provide side “walls,” or forms in order to achieve the desired dimensions of the footing, and in order to make sure the footing is perfectly level. This is super critical. The forms should be no less than 8″ in height. Since they’re used for leveling purposes and for maintaining the dimension and form of the upper part (the part that the first course of your limestone wall sits on) of the entire poured footing, it’s not necessary to make the forms as deep as the trench into which you’re going to pour the concrete (but make sure that the unformed, deeper part of the trench is flat along its bottom, and that it’s at least as wide as the distance between the inside walls of the two forms). As long as at least the top 8″ of the footing are formed, and the forms are perfectly level along their entire lengths (this guarantees that the poured footing will also be perfectly level), you’ll be good to go. Attach stakes (usually wooden dimensional boards like a 1x2s, 2x4s, etc, sharpened at one end) to the forms so that the tops of the stakes are exactly even with the top of the forms, and make sure that the stakes are long enough to hold the forms firmly in place during the pour. Since the tops of the stakes are flush with the top of the forms, you can rest your level on them when leveling your forms. If you’ve got chase pipes (for electric/water lines) that will be running through your footing, now’s the time to make sure holes have been drilled through the walls of the forms, and that the length(s) of chase pipe that will be travelling through the poured concrete are in place. Before you pour the concrete, make sure to oil the interior walls of your forms. Use a paint brush to lightly brush motor oil on those inside walls. This will make the forms a million times easier to remove after the concrete has set. The forms themselves can be constructed from a number of different materials, but are typically wood or flexible plastic. For my curving, continuous footing, I used 12′ lengths of vinyl soffit material ripped (longitudinally sawn) to 8″ widths and overlapped to achieve a longer continuous run than the 12′ individual lengths allowed. Their flexibility allowed me to easily create the curving, sinuous shape of my footings, and the limestone walls that I built on them. (Just this last fall, I built a short wing wall extension of my existing first phase planter, in order to extend the existing wall about 22 inches back to my new fence line. For this, I constructed wooden forms for the short footing, and cut the boards to a width of 18 inches (longer than necessary, but just fine for this short footing).
- Pour. Your forms are in place, any and all chase pipes are routed through the forms, and the insides of the forms are oiled. Time to pour the concrete. I recommend a high-strength concrete that features reinforcing fibers in its mix. You can also add rebar (steel reinforcing material) for additional strength. I used the high-strength mix with no rebar. You’ve got some choices in terms of how your concrete comes to your worksite. If you’ve got lots of linear feet of footings formed and ready to pour, I highly recommend a truckful of ready-mix high strength concrete. You’ll probably want to enlist the assistance of a helper if you’re going to be wheeling the concrete from the mixing truck to your waiting footing forms. If you’ve got access to a gas-powered or electric mixer, you can order the individual components of the concrete and mix it yourself on-site. Finally, you can buy individual 80-pound bags of high strength concrete and mix it yourself on-site. This last choice works well for shorter and shallower footing pours. After your footing forms are full to the very top with newly-poured, fresh, wet concrete, you’ll need to float, or smooth, the surface of the concrete. A uniformly smooth, flat and level surface is necessary for bedding your first course of limestone in mortar.
A few final concrete pouring Dos and Don’ts:
Do mix your concrete according to existing field conditions and current and predicted weather conditions. In hotter weather, mix your concrete a bit “looser.” This means that the concrete will have a higher water content which will in turn allow for greater and lengthier workability. In cooler weather, you can mix up “stiffer” (less water content) batches.
Don’t add too much water to your concrete mix. Too much water can take the mixture beyond its maximum saturation point. At this point, the mix will have lost the ability to reconstitute and it will not cure/reconstitute properly.
Don’t pour concrete if rain is forecasted within 24 hours of your pour. It’s not necessarily the end of the world if it rains within this time frame, but it can cause problems. Play it safe and wait until you know it’ll be dry for a couple of days.
Don’t pour concrete if temperatures below 40° Fahrenheit are predicted within the 24-48 hours after your pour. Cold temperatures interfere with the curing process and can compromise the strength of the concrete.
Do remove your forms 48-72 hours after pouring your footing. The form oil you applied to their interior surfaces guarantees that they won’t stick to the concrete when you pull them out. Remove the forms slowly, carefully, and as gently as possible.
DO MAKE SURE THAT THE SURFACE OF YOUR FINISHED CONCRETE FOOTING IS TOTALLY AND COMPLETELY CLEAN AND FREE FROM DIRT AND DEBRIS BEFORE ATTEMPTING TO LAY ANY LIMESTONE!!!
In your “How to Build a Stacked and Mortared Limestone Wall” game plan, your poured concrete footings figure big. Their proper construction and implementation is critical. Pour your footings the right way, and you’ll have successfully completed the first major construction step of your project, and you’ll have provided your wall with the proper base it will need in order to stand the test of time.
If you’re interested, check out my six-minute YouTube video about building forms and pouring a concrete footing. It’s got all of the qualities you’ve come to expect from a RGG video: terrible cinematography, crappy screen presence, lousy acting, and decent info. For much more technical/detailed, expert information on concrete and its applications, please visit the excellent website, Concrete Construction.
9. Lay Your Limestone
This it, gang – the moment we’ve all been waiting for: The nitty-gritty of how to build a stacked and mortared limestone wall. I’m going to try to break this down so it’s simple to follow and easy to understand. In this section, I’m going to explain how to go about laying the individual stones so that the stacked and mortared limestone wall you’re building is level and plumb (important for structural, aesthetic, and practical purposes), is indeed structurally solid and strong, does not let soil leech out (if the walls are being built to form a planter or retaining wall), and achieves the same “relaxed and natural” appearance as that of a dry stacked wall. To accomplish these things, we’ll make each of the following items a checkpoint in the limestone laying process: A) Set up a lengthwise level benchmark. B) Mix high-strength structural mortar appropriately. C) To achieve the look of my limestone walls, mortar joint thickness will vary between approximately 3/4″ to 1-3/4″ in thickness (due to the irregularity/non-uniformity of the individual stones). D) Thoroughly wet (with clean water) each individual stone prior to laying it. E) Only slightly recess, from the face (front) of the wall, the horizontal (and vertical) mortar joints which bed the first limestone course to the footing. F) Continually check side-to-side and front-to-back level of individual stones as you lay them. G) Continually check plumb (vertical straightness) of the wall as you lay each stone. H) For all mortar joints after the initial bedding mortar joint between the first limestone course and the concrete footing (which is the broadest mortar joint), restrict your mortar application to approximately the back (away from the face of your wall) 3/5 portion of each stone in order to achieve a recessed mortar joint. I) Fill verical mortar joints from the top. J) Fill any and all gaps on the backside of your limestone wall (inside wall(s) if you’re building a planter or retaining wall).
A) Set up a lengthwise level bench mark. Do this with a string line and a string level. Drive a wooden stake into the ground at each end of the length of your footing, right up against the face of the footing. Run a level string line between the two stakes (using the string level) at the height you’d like to set for the top of your first course of limestone. Base this height on one of your thinner first course stones bedded on top of a roughly 1-1/4″ thick mortar joint. This level string line, set at this height, will be your guide as you lay your stones, one by one, on top of the footing, and all along its length. If you start with one of your thinnest stones, any subsequent thicker stones that you lay on the footing will “smush down” the thickness of that first, bedding mortar joint as you hold each stone’s top to the level string line.
B) Mix high-strength mortar appropriately. The type of mortar you’ll absolutely need to use for your limestone wall has a mix ratio of 2 parts cement, 1 part lime, and 9 parts masonry sand. Mortar mixed in this ratio develops a compressive strength of 1,800 pounds per square inch, and is known as Type S mortar. It’s super strong, and is perfect for structures like those we’re talking about here. You can mix this stuff up yourself if you’ve got a gas or electric mixture AND you know what you’re doing, or you can buy it in 60-pound or 80-pound bags, already with the correct ingredient ratios – all you’ll need to do is add water and mix it up. For detailed information on Type S, and other types of mortar, please visit the excellent Gambrick website.
Since you’re going to be laying fairly large, irregularly sized and shaped stones on this stuff, it’s best to use a slightly stiff mix. If the mix is too loose and soupy, it will not properly support the individual stones as you try to lay them. But remember, if you’re working with a slightly stiff mortar mix in hot weather, it will begin to set fairly quickly. I’d suggest mixing smaller batches at a time, and keeping your mixing box/trough covered, and maybe giving the mortar inside a light, occasional misting of water in order to keep it workable.
C) To achieve the look of my limestone walls, horizontal mortar joint thickness should vary between approximately 3/4″ to 1-3/4″, and vertical mortar joints will vary from approximately 1/4″ to 1-1/2″ in width. (These variations in mortar joint thickness and width are due to the irregularity and non-uniformity of shape and size among the individual stones. I believe that these variations – in both the stone and the mortar joints – contribute to the more natural, relaxed look of my limestone structure. If you allow your own mortar joints to fall – and vary – within these tolerances, and you recess all of the mortar joints above the first course of limestone (you’ll read about this very shortly), your limestone walls will achieve a look that’s similar to mine.
D) Thoroughly wet (with clean water) each individual stone prior to laying it. If at all possible, immerse each stone completely in clean water in a bucket or spare mixing box/trough and let it soak for a bit (less than a minute has always worked for me). If you can’t soak the stones, at least thoroughly hose each one off before working with it. The water rinses off any dust particles which could interfere with the setting/bonding process. It also saturates (to a degree) the porous stones, which makes them more amenable to bonding to the mortar.
E) Only slightly recess, from the face (front) of the wall, the horizontal (and vertical) mortar joints which bed the first limestone course to the concrete footing. That first course of limestone, I feel, should have an amply broad bedding mortar joint. This first joint, which is the one immediately between the surface of the concrete footing and the first limestone course, is by far the least noticeable. No one will see that it’s not recessed back as far as those of the higher limestone courses. Trust me on this one. See the pics immediately below.
F) Continually check side-to-side and front-to-back level of individual stones as you lay them. By using your level string line (which you’ll adjust upward on the stakes as you begin each successively higher, new course), and your masonry level, it’s fairly easy to maintain level for these stones. When you use the level, from side-to-side, simply place it so it spans from high point to high point on each stone (remember, the stones are irregular in size and shape). As the width of the wall is equal to the width of only one stone, checking front-to-back level will not quite yield exactly level results. You’ll see in checkpoint “G” below that continually checking for plumb will help keep your wall’s front-to-back level within acceptable limits.
G) Continually check plumb (vertical straightness) of the wall as you lay each stone. Keeping the wall plumb as you build it is critically important. Nothing will more seriously compromise the structural integrity of a stacked and mortared limestone wall than a “lean” or “tilt” to its structure. Checking and maintaining plumb as you build your wall is surprisingly easy. Use the front, or face, of the wall as you benchmark, and hold your level from the most prominent point of the stone you’re currently laying to the most prominent point of the stone immediately below it. By keeping these prominent points plumb, and continuing to check and lay in this fashion, you’ll end up with a wall that’s just about perfectly plumb. The process just requires consistency and diligence. And you’ll notice, as you build your side-to-side level, and vertically plumb wall, the individual stones will sit virtually level from front-to-back, as well.
H) For all mortar joints AFTER the initial bedding mortar joint between the first limestone course and the concrete footing (which is the broadest mortar joint), restrict your mortar application to approximately the back (away from the face of your wall) 3/5 portion of each stone in order to achieve a recessed mortar joint. Trowel enough mortar onto the stone(s) below the stone that you’re about to set in order to achieve a fat spreading of mortar that covers the back 3/5 (approximately) of that lower stone(s). When you set your current stone on top of this mortar joint, some of the mortar will squeeze backward to eliminate any possibility of recess on the back of the wall (the inside wall of a planter), and some of the mortar will squeeze forward a bit to create a good looking, and structurally sound recessed mortar joint. You can use your pointing irons and/or jointing tools (or even a gloved finger) to work any forward “squishing” mortar back from the face of the wall. See the photos immediately below.
Knowing how to build a stacked and mortared limestone wall so that it looks natural and “relaxed” when it’s finished implies a couple of things. First, keeping the mortar joints recessed from the face of the wall as described above, plus allowing moss to grow on the stone and mortar, really help give my limestone structures a natural feel. See the four pics below.
I) Fill vertical mortar joints from the top. The vertical mortar joints are easy to fill from the top. Of course, as you lay each stone, you can smear some mortar along its edges (keeping it recessed from the face of the wall, as I’ve been preaching here). But once two stones are set next to each other, it’s really simple to stuff mortar into the space between them from above. In any case, keep the mortar joint recessed from the face (just like we’re doing with the horizontal mortar joints). There. I said it again. Check out the pics below to see what I’m talking about.
J) Fill any and all gaps on the backside of your limestone wall (inside wall(s) if you’re building a planter or retaining wall). This totally prevents soil leakage (if you’re building a planter or retaining wall) and will contribute to the wall’s further strength and structural integrity. And doing it should be fairly easy, since you’ve kept your mortar application toward the back 3/5 of each limestone course. Although you may want to use your brick trowel or pointing irons to smear more mortar along the back (inside) of your wall(s), enough mortar should have “oozed” out the back of each mortar joint (due to the weight of the stone being set upon it, and the actions of setting that stone) so that a smoothing action of that “oozed-out” mortar should be enough to fully seal the back of the wall. In addition to the mortar that oozed out the backs of the mortar joints, I did apply additional mortar to the inside (back) walls of my planter, further sealing it, and increasing its structural integrity. The two photos immediately below demonstrate the appearance of my filled and sealed back (inside) faces of my limestone planter’s walls.
Note: As I mentioned back at the beginning of this article, when you build stacked and mortared limestone walls for a planter like mine, and your land’s substrate is clay, or some other poorly draining material, I strongly advise excavating down approximately 18″ below the existing level of your new planter’s “floor,” removing the clay (etc) to this depth, and replacing it with sand or 3/4″crushed stone. Your stacked and mortared planter will not allow drainage if its floor is clay. Adding a layer of sand or 3/4″ crushed stone, as I suggest here, will add drainage capabilities to your new planter.
Some notes about weather, moisture, and mortar: As is the case with concrete mix, if you add too much water to your mortar mix, you’ll wreck it. And I keep the same weather eye on the atmospheric conditions of my stone-laying activities as I do with my concrete pouring activities. Don’t work with mortar when rain is in the forecast within 24 hours of the completion of your work. Don’t work with mortar if the temperature is expected to dip below 40° Fahrenheit within 24 hours of your job completion. However, if you’re mortaring your limestone wall on a hot and dry day, it’s not a bad idea to LIGHTLY MIST your work with water when you’ve wrapped up. And I do mean LIGHTLY, and I do mean MIST. A super light misting from your hose nozzle’s finest setting on a hot and dry day is good for the mortar’s curing process, and prevents any potential cracking that may occur as a result of the mortar baking in the sun and drying out too quickly.
Here in Step 9, you learned the A to Z (ok, the A to J) of actually laying the stones. (If you’d like to check out a video of yours truly building the short limestone wing wall section of my first planting feature, click here. It’s another typical shitty RGG production, but it’s actually fairly illustrative.) The fact that you’ve gotten this far means two things: 1) You’re well on your way to learning how to build a stacked and mortared limestone wall, and, 2) You’re only gonna have to put up with me for one more step…
10. Use Concrete Blocks (CMUs – Concrete Masonry Units) When Possible in Non-visible Locations
Yep. Concrete blocks, or CMUs, in construction parlance. When you build a stacked and mortared limestone wall, you’ll want to use these whenever and wherever you can. They’re structurally sound, they support incredible amounts of weight, and they take up a lot of vertical and horizontal space. This last means that where you’ve got CMUs, you don’t have smaller, trickier stones. And that means less work for you, and less time spent screwing around. But if you’re wondering how to build a stacked and mortared limestone wall with a bunch of concrete blocks, and still have it look beautiful and relaxed and natural, you can wonder no more. The way to make sure that CMUs don’t screw up the look of your wall is to use them in places where they won’t ever be seen. My limestone planter design scheme serves up a perfect example of this kind of situation. My first planter section leads to the second section, which will be approximately twice as tall as the first. The lower section shares a wall with the taller section (which has yet to be completed). This shared wall provides the perfect opportunity for CMU use. The CMUs are buried in the soil of the first, lower planter section, and only the stacked and mortared limestone upper portion (which has been laid on the buried CMUs) of this shared wall is visible. The shots below show this shared wall, and illustrate how CMUs can be cleverly – and totally unobtrusively – incorporated into the structure of a stacked and mortared limestone structure.
Now that you can see how useful the incorporation of CMUs can be in the construction of a stacked and mortared limestone wall, I’ll give you a quick rundown of the things I do to make sure that the concrete blocks that I incorporate in my limestone structures are installed properly, and that they’re more than strong and solid enough to provide permanent support for the courses of stone that will be laid on (or next to/in front of) them. Install them onto your concrete footing and do this:
- Mortar-fill and fully point them. The 8″x16″ CMUs I use have hollow channels running through their centers. When I lay these blocks, I fully point the mortar joints (not recessed), and I fill the hollow channels with mortar. This makes any wall built in this way incredibly strong, completely immovabale, and totally permanent. In other words, such a wall is the perfect base for a bunch of stacked and mortared limestone. Below are some pics illustrating the appearance of filled and fully pointed CMUs.
- Use brick ties. A brick tie is a strip of galvanized, thin gauge, profiled and perforated steel designed to fit permanently in a mortar joint and protrude so that it can be incorporated into a successive, adjacent mortar joint, or mechanically fastened to an adjacent, non-masonry surface. I use these to tie my CMU walls horizontally to adjacent stacked and mortared limestone walls, or to adjacent, non-masonry structures like my laminated, treated wood planter backs (of which you’ll read in a future article). If the CMU portion of your wall is transitioning, horizontally, to a limestone portion (as in the case of a particular stacked and mortared limestone wall section extending from the front of a CMU wall section, in order to obscure it), you’ll want to use brick ties to effectively bond the two different types of wall together. Just embed the protruding ends of the brick ties (protruding from the CMU wall portion) in the corresponding mortar joints of the adjacent limestone wall. Below is a shot of protruding brick tie ends ready for embedding in the mortar joints of the limestone wall which will extend horizontally from, and obscure the CMU wall.
A “How to Build a Stacked and Mortared Limestone Wall” article wouldn’t be complete without a few pics of the wall(s) in question, in limestone planter form, with stuff growing all over them. Here you go. Thanks in advance for indulging me.
How to Build a Stacked and Mortared Limestone Wall: Now You Know
Well, gang, we’re at the end. And now, you really do know how to build a stacked and mortared limestone wall. If you’ve stuck the whole thing out, I am grateful. And I commend you. There was a lot of info to soak up here. But as a result of hanging around until the final note, you know what the difference is between a dry stacked wall and a stacked and mortared wall. And you know my 10-Step plan for thinking through, designing, and building limestone walls of the stacked and mortared variety. In the not to terribly distant future, and right here on The Renaissance Garden Guy, you’ll read about my methodology for building the heavy, laminated, treated wood planter backs that I’d mentioned earlier, and which you’ve no doubt spotted in a number of the photos in this article. They’re an integral part of my stacked and mortared limestone planters, and although they’re not the only option for an effective back for this type of planter, they’re definitely a damned good one. But this topic is for another article, and for another time.
For right now, you’ve taken it all in, and, once again, you’ve got what you need to know to build a stacked and mortared limestone wall. Damn, guys and gals, you did a great job!
Thank you again for sticking this one out. Your kind interest and readership is always dearly appreciated.
Cheers, and Happy Gardening!
The Renaissance Garden Guy is a participant in the Amazon Associates Program. As an Amazon Associate, I earn from qualifying purchases.
Please click here to view The Renaissance Garden Guy Disclosure page.
Your garden is totally amazing. I drool.
Thank you so much, Annie! I’m glad you’re liking the garden. Reading your kind words here make all the work more than worthwhile. Thank you again, Annie – I truly appreciate it!
Amazing article, can’t get more precise than this….
Beside the knowledge, the writing, the beautiful images… Your work is fascinating !!! It’s because you put so much love and passion into it … this is the only way to accomplish greatness and beauty.
You should write an encyclopedia of gardening, your knowledge is amazing 🙏❤️🌸 THANK YOU
Thank you so much for these incredibly kind words, Roxxy! I cannot tell you enough how much I appreciate your kindness and your interest. I’m so glad you enjoyed this article, and that you like my gardening material. It’s so encouraging to read such lovely thoughts and enthusiastic praise. Bless your heart, Roxxy. And thanks once again!
The limestone walls add an incomparable dimension to any garden. Your project is ambitious, and your work is amazing. The process is truly fascinating. Great article.
Thank you so much, Mary! Such lovely compliments – I’m humbled. I’m so glad you’ve enjoyed reading about my limestone projects, and I’m thrilled with the fact that you like the way that they’re shaping up. As much as I enjoy the design and construction processes, I’ll be more than happy when the final stone is laid (I actually see piles of that stuff in my dreams)! Thanks once again!
As always a great article with a lot of great information. When I see your planters and walls, it makes all of your hard work come to life. I also wanted to let you and all of your readers know that I just finished reading April Doyle’s book “Hive”. It was a good read. If any of you have not read it go and check out John’s book review.
Thank you so much, Kevin. I’m glad you enjoyed the article, and I’m glad you like the limestone monstrosities I’m building in my garden. I think stone structures like these add an amazing dimension to a garden, and are well worth any effort involved in their construction. I do enjoy the construction process, but I’ll really be glad when I’ve finished building these things! And I’m so glad you enjoyed reading April’s novel. I thought it was a terrific, fast-paced read. Thanks for the feedback!