Various Types of Materials for Constructing a Retaining Wall!
Monalisa Patel is a Structural Engineer who has earned her Master’s degree (ME) from the L.J College of Engineering and Technology Ahmadabad in 2018. She is an Engineer (Civil) at SDCPL – Gharpedia. Helping people to solve their queries about construction is her passion. Apart from being blogger, she also participates in structural design at SDCPL. She is reachable on LinkedIn, Twitter, Instagram & Facebook.
A retaining wall is a structure that is used to support the soil mass laterally, so that the soil on one side of the wall is retained or preserved when the levels are different on either side. Thus, retaining wall is constructed for the purpose of holding soil. Walls that are normally constructed while raising general structures bear vertical loads, whereas retaining walls are specially meant to bear horizontal loads. According to ‘Frederick S. Merritt & Jonathan T. Ricketts’ (Author of Building Design and Construction Handbook), A retaining wall is defined as a structure whose primary purpose is to resist the pressure exerted by soil, rocks or even water pressures. In some exceptional cases, such as basement walls and certain types of bridge abutments, it may also support vertical loads.
The strength of the retaining wall is merely dependent upon the height difference on both the sides of wall and the height of the wall above the finished ground level on higher side. Thus, while constructing such walls, utmost importance must be given to these details as they will ultimately define the strength you require.
Remember, when you use retaining wall in landscaping, even the aesthetical aspect needs to be taken into consideration along with its strength. Hence, the choice must be a balanced one. However, if the height is not more, the strength is not critical.
In many situations (gardening) the loads are not that substantial, so the load-bearing capacity of the wall is mostly determined by the material used in constructing the wall. We have already discussed various types of retaining walls. Here, we shall discuss some of the most commonly used retaining wall materials and understand how best they can play their role in adding beauty to it.
Retaining Wall Materials
01. Stone Veneer as a Retaining Wall Material
Stone veneer is a protective material that can be used in retaining wall as a decorative covering for vertical walls and surfaces. It does not hold load bearing capacity. This means, stone veneer is completely an aesthetic element and it needs a solid core to even work as a wall. It looks wonderful and brings enough of its own unique personality to earn a spot on the list.
Advantages of Stone Veneer as a Retaining Wall Material
Durability – The natural stone is a superior material for retaining walls. Stone Structures are capable of withstanding weathering effects i.e. snow, rain, heat, cold etc. Thus, your wall will also have the capability of resisting all these.
Appearance – Natural stone has a very beautiful texture and look. Beautiful patterns, colours, unique shapes or even the lichen growing on the rock are some noticeable features of these materials.
Light in Weight – Although it is not claimed to be amongst the lightest materials in the market, stone veneer is yet reasonably lighter in weight.
Flexibility – The solid core can be built literally for all height and thickness.
Disadvantages of Stone Veneer as a Retaining Wall Material
High Cost – Unlike some others manufactured materials, natural stone is not available at an affordable price. Retaining wall made of stone veneer will prove a bit costly.
Installation – Installation of stone veneers generally involves skilled masons and a professional contractor.
Design Problems – Matching all the single pieces with existing architecture is not always easy.
Solid Core – Stone veneer alone as retaining wall material is not a freestanding element, so you will have to double the work.
02. Natural Stone as a Beautiful Retaining Wall Material
In a sense, natural stone retaining walls are very similar to boulder walls. The only obvious alteration is that natural stone pieces are much smaller than boulders. But that makes all the difference in the world. Natural stone, therefore, retains all the good qualities of other types of stone (tradition, strength, durability), while allowing you much more design options than boulder pieces.
According to ‘SP 20(S&T): 1991’ (Handbook on Masonry Design and Construction), Mostly stone retaining walls are built either in dry random rubble masonry or dry coursed rubble facing masonry with a backing of random rubble masonry. The former is mostly constructed in areas with thin population where appearance is not of much consideration whereas the latter in thickly populated areas, where appearance is an important criterion.
Advantages of Natural Stone as a Beautiful Retaining Wall Material
Appearance – Natural stone look amazingly beautiful, and fit perfectly into any kind of traditional rustic setting. Because you are working with smaller building blocks you will have more freedom to experiment with different textures and colours.
Tradition – Natural stone is one of the oldest and the most reliable retaining wall materials used for grade transitions.
Durability – Much like any other stone masonry construction, if constructed well, natural stone can last for years.
Disadvantages of Natural Stone as a Beautiful Retaining Wall Material
High Price – Stone was always considered to be one of the more pristine, but also the most expensive retaining wall materials.
Drainage Problem – When it comes to natural stone, drainage can become a serious problem after a short period of time.
Heaviness – Setting up a stone wall is a very labour-intensive process. Handling and transportation of stone is not easy as they are heavy in weight.
Stone Masonry is weak in tension. It may collapse or slide under tension. Hence, you must use adequate bond stones, cornerstones for its long life.
Also Read: Know All About Stone Masonry
03. Use of Limestone as a Retaining Wall Material
Limestone is a sedimentary rock. Its primary materials are aragonite and calcite. Although one may think that limestone is more fragile than traditional rock, but it is interesting to know that some of the most long-lasting structures in the world like Taj Mahal and Great Pyramids of Giza are made out of limestone. Like any other material, Limestone to has its advantages and disadvantages.
Advantages of Limestone as a Retaining Wall Material
Appearance – Limestones are usually grey or yellow in colour. They give a very classy and timeless feel to the space they occupy.
Durability – Limestone is weather-resistant, fireproof, bug-resistant, and impact-resistant. Even with the passage of time, it remains unaffected and does not lose its beauty and visual appeal.
Easy to Maintain – The best part is, limestone retaining walls are very easy to clean and maintain. They only require a gentle brush.
A Variety of Options Available – There are lot of options available in Limestone as it gives ample variety to choose from. Sandblasted, split-faced, polished, rubbed, grey, silver and variegated are some of the types of the limestone available.
Disadvantages of Limestone as a Retaining Wall Material
Susceptible to Chemicals – Though Limestone is weather-resistant, it is also susceptible to chemicals. The most common cause of weathering is rainwater with high carbon dioxide.
Susceptible to Staining – Due to its highly porous nature, limestone is very susceptible to watermarking and staining caused by other liquids.
04. Boulders – The Oldest Retaining Wall Material
Boulders are one of the oldest retaining wall materials. They are the largest type of natural stones available which provides a miscellany of shapes and sizes and demands less maintenance. Unlike quarried stone or manufactured modular blocks, boulders are widely available and ready to use for retaining wall construction even without additional refining. At the same time, they retain most of the positive aspects of the furnished stones and can last for long.
Advantages of Boulders as Retaining Wall Material
Natural Look – Boulders are a great match for any kind of landscaping design and rustic style.
Easy to Use – Boulder retaining walls are very convenient to build. Some of the retaining wall can be easily constructed simply by stacking the boulders on top of each other i.e. dry wall
Availability – Boulders of all sizes and colours are easy to obtain.
Durability – As we have mentioned earlier, boulder constructions were in use since the beginning of human existence. Some of them still exist in a better condition.
Disadvantages of Boulders as Retaining Wall Material
Size – Boulders tend to be quite large. So, if you own a smaller yard, you must probably skip this idea as they will occupy a lot of space.
Transportation – If the blocks are not locally available, then transportation is not easy and it will turn out to be expensive as well.
Height – Boulder retaining walls can not be constructed as high as concrete walls as stone masonry is weak in tension.
05. Gabion – A Flexible Retaining Wall Material
Gabion is also a very old and traditional method of building the retaining walls. The name ‘Gabion’ is derived from the Italian word Gabbia which stands for cage. They are simple cages made out of steel rod or wires and filled with rock/stone or rubble.
Gabions are flexible materials and ideal for retaining walls, particularly in landscaping. On one end they look natural and beautiful, and on the other end they being flexible, they do not suffer much stress. Hence, distresses due to horizontal or vertical movement of soil do not cause substantial settlement or sliding.
Advantages of Gabion as a Retaining Wall Material
Heavy Basis – Gabion walls can stay firm in any position, even during the worst downpours.
Flexibility – Gabion is a wire container or ‘a basket.’ Thus, it is very flexible and extremely easy to fit in any type of backyard setup.
Upgradability – Gabion walls are modular. It means that each of their sections can be easily upgraded or replaced. Also, the gaps between concrete pieces or rock can be filled with vegetation and silt which should further reinforce the wall.
Ease of Use – Gabion retaining walls can be built even with the slightest knowledge of masonry or architecture. The time taken for raising such walls is comparatively very less and transportation is also manageable.
Disadvantages of Gabion as a Retaining Wall Material
Visual Appeal – Although they can play along with a wide variety of riverside and coastal homes, gabion walls do not give a better aesthetical look and neither they are visually pleasing.
Prone to Rust – If you ignore the maintenance part, wire baskets can easily rust and render the whole setup worthless.
Vulnerable to Water – Exposure to water can damage the basket and cause the corrosion of cage and the materials inside. (Depending upon the elements)
If you wish to go for this option, you may require a large width. Hence, if you have limited space, this option would not be a feasible one as it will occupy major of your land, along the boundary.
06. Bricks – The Most Popular Retaining Wall Material
Brick is one of the most popular building materials, and it is very easy to deal with as well. Unlike concrete and stone, bricks give a very warm and inviting look. They do a wonderful job complementing traditional landscapes and homes. Bricks as retaining wall materials have a lot of other good things that makes them popular in the list.
Advantages of Bricks as Retaining Wall Material
Low Maintenance – Brick is a comparably low-maintenance building material. Also, it retains its colour so well that you don’t have to bother for painting too often.
Eco-Friendly – Bricks are made from clay and fertile land. Thus, they are eco –friendly. Also, bricks can be reused later for other landscaping elements like walking paths.
Weather and Fire Resistance – Bricks are not damaged by dampness. Also, bricks are not a combustible material; hence they do not spread fire.
Durability – A solid, well-made brick masonry retaining wall is nowhere near to the durability of the one made by stone, but still we can say that its durability is good.
Also Read: Various Shapes of Brick used in Construction
Disadvantages of Bricks as Retaining Wall Material
Colour limitations – Although they come in a range of different colours, compared to some other retaining wall materials, bricks do not offer a large variety of colours.
The Lack of Flexibility – As it lacks flexibility, changing the outer appearance is difficult, but replacing a damaged brick is even more problematic.
Like stone masonry, brick masonry is also weak in tension. Hence follow Codal provisions.
07. Wood as a Retaining Wall Material
Wood is amongst the popular retaining wall materials, but you need to be careful while selecting the type of wood, if you want to use it for retaining wall.
Advantages of Wood as a Retaining Wall Material
Natural Look – Wood retaining walls have a tendency to blend into the landscape quite seamlessly.
Cost – Wood retaining walls are normally very cost-effective.
Ease of Installation – Wood retaining walls are also very easy to install which makes them ideal for DIY landscaping project.
Lightweight – Although reasonably durable, wood is a very lightweight retaining wall material which is easy to dismantle, move around and reuse.
Disadvantages of Wood as a Retaining Wall Material
Limited Lifespan – Amongst all the retaining wall materials discussed here, wood probably has the shortest lifespan. Though with proper maintenance, you can increase the lifespan of the wood retaining wall.
Wood Rots – With proper treatment you can control the rotting of wood to some extent but not totally. If you are living in a place that falls under heavy rainfall region, you are advised not use this material.
Susceptible to Termites – This is the area where utmost care is required. If you do not maintain the wooden structure properly, then someday it will be susceptible to termites which will ultimately damage the retaining wall and backfill too.
08. Timber – A Durable Retaining Wall Material
Although, at the first glance wood and timber may seem to be the same, but they are not. The word timber is used for any stage of wood after the tree has been cut. The so-called “finished” timber is the wood that has been processed and cut into various sizes. Mostly they are of good quality and normally used as structural wood for buildings.
Advantages of Timber as a Retaining Wall Material
Durable – Thick timber pieces are more durable and much heavier than wooden planks.
Good-Looking – Timber as such possess natural charm. Thus, it ought to bring a lot of old-school charm in your backyard. It will also create a very strong impression on the viewers.
Easy to Install – Installation is quick and easy as you don’t have to use concrete or mortar in it. Timber retaining walls have a good structural integrity; even if you simply stack the pillars on top of each other and a nail them together.
Disadvantages of Timber as a Retaining Wall Material
Timber Rots – Although timber retaining walls are said to last at least for 15-20 years, but not many of them are this lucky as the rotting can affect its lifespan.
Lacks of Flexibility – Timber pillars are very bulky and large. Making any kind of advanced design with such retaining wall material is not easy as it lacks flexibility.
Susceptible to Termites – Again, like any wood, timber is also vulnerable to termites.
09. Concrete Blocks – Modern Retaining Wall Material
Concrete blocks are latest, modern and common type of retaining wall material. This is because it is produced artificially (Precast), and moreover concrete gives a lot of flexibility and variety to choose from.
Concrete walls are generally designed to be set on a compacted gravel base and remain strong even when pressure is applied to them.
Advantages of Concrete Blocks as Retaining Wall Material
Durability – A concrete wall has the best of longevity and can usually last up to a whole century.
Variety – Concrete blocks are available in different shapes and sizes. They can also be used to create curves.
Easy Installation – Concrete block walls are generally much easier to install than some other, more labour-demanding block types.
Low Maintenance – It has practically very low maintenance. Cleaning it once in a year is what is required.
Eco-Friendly – Moreover, concrete walls are non-toxic and eco-friendly. They do not emit dangerous chemicals or allergens.
Disadvantages of Concrete Blocks as Retaining Wall Material
Architectural Demands – Concrete block retaining walls have to be carefully designed, hence you must seek for professional advice for addressing drainage and other effective associated issues. Also, the lack of proper support may affect the durability of retaining wall.
Limitation on Height of Wall – Concrete block retaining walls can be used only for walls that are not taller than four to six feet. So, if you want to raise your rose beds at higher level, you will have to look for another option.
Complicated to Remove – If you ever want to change the placement of the wall, you will have to undergo a lot of difficulties to dismantle it.
10. Poured Concrete or Cast-in-situ Concrete as a Retaining Wall Material
Poured or cast-in-situ concrete is a very popular architectural option produced by pouring the concrete directly into the forms on the site. Since it looks very clean-cut, cast-in-situ concrete plays the best with the modern-looking surrounding. The ability of the concrete to support the soil load depends on weather conditions and other elements, apart from its thickness.
Advantages of Cast-in-situ Concrete as a Retaining Wall Material
Strength – Since it has higher density than blocks retaining walls, the walls built of cast-in-situ concrete are much stronger.
Variety – Concrete can be poured and shaped into any form you desire, which means it gives you a lot of design options to choose from.
Consistent Look – It looks consistent.
Flexibility – Poured concrete helps incorporating other architectural elements i.e. drainage systems very easy.
Apart from the retaining wall materials, we have also listed the masonry materials. Please check them here,
Disadvantages of Cast-in-situ Concrete as a Retaining Wall Material
Susceptible to Crack – Concrete walls generally need some kind of structural support (e.g. steel rods). If such supports are not provided to them, they may crack.
Building Requires a Lot of Skill – It requires skilful hands. Also, the forms in which you are going to pour concrete should be immaculate and perfectly set up.
Moisture – Retaining wall made with poured concrete when exposed to excessive amounts of water, concrete tends to become unacceptably damp. This may damage its surface treatment i.e. paint.
Vulnerability to Chemical Damage – Concrete can be easily damaged by a number of chemicals like sulfates, chlorides and even distilled water.
In brief, when it comes to residential retaining walls, there is a variety of materials available as discussed above. But there are certain things that need to be kept in mind – firstly, you need to decide the purpose of the wall, then the appearance you are desiring for and finally your budget while deciding the retaining wall material. Having understood the pros and cons of every material, now it is up to you whether you choose timber, stone, concrete block or any other material. We are sure that this article must have helped you in understanding the basics of retaining wall construction so that you can have the wall that has been designed and built flawlessly.