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In our guide you will find all the details in regard to the uses of cinder block, the cost of it as well as up to 4 free contractor quotes.
A cinder block is a man-made building block made from a special type of concrete. Both concrete blocks and cinder blocks use Portland cement to bind the aggregate together but whereas concrete blocks use between 60% to 75% of fine crushed stone and sand, a cinder block will use the same amount of coal cinders or ash.
Are there any other names?
Sure there are. As usual the names vary depending on what English speaking country you are in. So we all know what we are talking about let’s just run through the differing names and where they are used.
Cinder blocks – USA. These are made from cinders or otherwise known as fly ash or bottom ash.
Breeze blocks – UK. Breeze is another name for ash.
Hollow blocks – Philippines. Often the blocks are constructed so as to be hollow.
Concrete blocks – Canada and New Zealand.
Blocks – New Zealand.
Construction blocks – New Zealand.
Besser blocks – Australia. The US Company ‘Besser’ used to be a major supplier of concrete block making machines.
Clinker blocks – These are the same as cinder blocks only made with clinker rather than ash.
Although these are all basically the same product, the terms ‘Cinder block’ and ‘Breeze block’ are used in general usage to mean all of these different types.
Cinder blocks are made in exactly the same method as regular concrete blocks except that the aggregate is replaced with cinders and fly ash. When coal fired power stations and steel smelting centrers were prolific worldwide there was a substantial problem of what to do with the waste products, namely the ash, clinker and other non-combustible by-products. Bottom ash, also known as clinker is the non-combustible part that settles at the bottom or sticks to the side of a furnace. Fly ash is the non-combustible part that is finer than bottom ash and escapes the furnace with the flue gases.
As clinker and ash mainly consists of silicon dioxide, magnesium dioxide and other non-combustible minerals naturally found in coal, incorporating these minerals into a construction block became a cheap and useful way of using the waste products from power stations and other furnaces. The minerals found in the furnace by-products are the same as those found in sand and other types of rock.so rather than having to mine or quarry the raw aggregate for concrete production there was a ready to use waste product.
The use of ash and clinker tend to produce low density blocks suitable for non-load bearing walls. They are also used outside as garden walls and single skin shed and garage walls.
As a direct result of the low density they are also very lightweight so a bricklayer will prefer to use cinder blocks if it is possible to use them. Because they are used as non-structural walls, cinder blocks are sometimes produced with hollow centrers to make them even lighter and to improve their thermal insulation properties.
The standard nominal sizes of cinder blocks available vary depending on which country you are in:
USA – 155/8” x 75/8” x 75/8” (410 mm x 200 mm x 200 mm)
UK and Ireland – 440 mm x 215 mm x 100 mm (17.3” x 8.5” x 3.9”)
New Zealand and Canada – 390 mm x 190 mm x 190 mm (15.4” x 7.5” x 7.5”)
Because cinder blocks are not designed to provide structural support they can only be used in a domestic setting as internal non-structural walls and as partitions. In exterior applications they can be used as garden walls, retaining walls, or purely ornamental structures.
Because they are made from concrete in molds they can be literally any shape you might like. In practice, they come in a variety of standard styles to suit different needs.
Standard. This one is also known by the name ‘Concrete Masonry Unit’ or CMU. The blocks measure 155/8” x 75/8” x 75/8” which means that when you add on the standard thickness of a mortar bed (3/8”) you will get exactly 16” x 8” x 8”.
Half blocks. This is half the length of a standard block. They are used to finish walls smoothly and are useful when building curved walls.
Sash. This type of block has a notch cut to accept casement windows. This is usually seen in the construction of sheds.
Rounded corners. Also known as bull nose blocks. The round can be on any of the corners or all of them. They are very useful when dressing an edge and preventing the block from having sharp corners.
Headers. These blocks have slots designed to accept frames.
Jamb joists. These have slots designed to accept wooden door and window frames. They are usually used when a garden wall has a gate or other opening or in structures such as sheds.
Capstones. These blocks are flat and decorative and are shaped to finish off the top of a freestanding wall.
As stated earlier, cinder blocks are mainly used as internal non-structural walls or external garden, retaining and shed walls. From this we can see that the most likely contractors to use this type of block would be bricklayers and masons or gardeners and landscapers depending on who is most relevant to the job.
Yes you can build a cinder block wall as long as you can physically lift the blocks, mix up some mortar, use a spirit level and lay the blocks in a straight line. The biggest advantages in doing this work yourself are that you will not have to pay for the labour to build the wall and you can spread the work over as many of your spare time hours as you need. Some people even regard laying blocks as a very therapeutic hobby.
Ok. So you want to have a go at building a cinder block wall, do you? Well there is a bit more to it than just laying one block on top of another. If you really want to learn however then read the following section and see if you still want to do it after you have seen the steps.
The purpose of the wall will define how you intend going about the task of building the wall. The different types of wall could be:
A standard wall. This can be for decoration in the garden or for privacy in place of a fence panel. This has to be able to support the weight of the blocks above them and also be able to withstand wind and other types of bad weather.
Retaining walls. These walls are to stop the ground from eroding or to lessen a very steep slope. This needs to support the weight of soil and underground water pushing laterally against the wall.
Check in your deeds and at City Hall to find out if there are any covenants or regulations about how high garden walls can be. Often any wall less than three feet in height does not need a permit. Anything above this and most retaining walls will need a permit. If you are building a small retaining wall well away from your property borders to form terraces in the garden or for a similar purpose then probably you won’t need a permit. If you aren’t sure whether you need a permit or not then just go to the permit office and ask.
When you build a wall, it isn’t just a case of mix up some mortar and off you go. You need to do some fairly rigorous planning first. After drawing the required shape on paper, you need to mark out the perimeter on the ground using string and stakes. This will give you a better idea of the physical limitations of your wall and whether or not you have to change anything.
It is less expensive to move a piece of string and a couple of stakes than it is to move a half built wall. If you intend laying out curves on the ground then use non-toxic paint (you can buy aerosol cans of special paint) or even use garden hosepipe to describe the contours and curves.
The next step is to start thinking about the foundations. This involves digging a trench in the ground so before you start to make any holes get in touch with your utility companies to find out if there any pipes, drains or cables in the way. When you dig your foundation trench you will need to go at least one foot down (the depth of trench depends on the height of your walls).
If you live in a cold region then you will need to go down at least a foot below the frost line, this will prevent any expansion and contraction from putting any unnecessary stress on the concrete. Once you know where your utilities are you can dig. If you have got pipes or cables in the way then ask the utility company to reroute their service line. Let us assume there is nothing in the way.
You will need to dig a trench to the required depth. It is probably worth getting advice here from a trained and licensed bricklayer or architect on the correct depth and width for your foundations. If your ground is sloped then you may have to build your foundations in steps. Once again get a qualified professional to help you with this. You will find that the width of the trench should be about twice as wide as the thickness of the wall.
Let us assume you have dug the trench to the correct depth and the correct width and the bottom of the trench is dry and level. Pour the correct amount of concrete into the trench (you will need a minimum of four inches deep concrete to provide a stable footing but once again get advice depending on the height of your wall). Make sure the surface of the concrete is level and tamped down so all air bubbles have been removed.
While the concrete is setting mix up a bit of mortar and practice laying some blocks somewhere out of the way. Practice getting the gaps between blocks the correct distance and get the correct consistency of mortar. It is much easier to take some time getting it right before you start on the actual wall.
Never skimp on the mortar. If you have about 100 feet of wall then you will need about three cubic feet of mortar. Basically multiply the length of the wall by 3%, so a 100 ft wall needs 3 cubic feet, while a 150 ft wall needs 4.5 cubic feet of mortar. Remember when you are laying the mortar bed you will need about 3/8” between each block and between each layer. If you are using hollow blocks (and if the wall is retaining or if it is tall then I would recommend it to be hollow with reinforcing bar and cement infill), then allow enough mortar to fill the cavities. Usually about one cubic yard of concrete or mortar will fill 74 standard cinder blocks. Don’t be exact on this figure; always get a bit more to allow for wastage and settlement.
These bars, also known as ‘rebars’ are shaped like a capital letter ‘L’. Submerge the short arm in the concrete footing with the long arm sticking vertically upwards. Make sure the bars are about two or three feet apart and will either be inside the block cavity or are on the hidden inside surface of the wall. The rebar and concrete infill are there to absorb some of the loads pressing against the wall from the soil and water in the retaining wall.
Rebars cost about $0.80 per foot and are sold in lengths starting at two feet. When buying rebar, it is often more economic to buy the bar in the longest length you need as usually the cost of long lengths is less than shorter lengths. For example a 10 ft x 0.5” rebar could cost about $4.50 while the 2 ft x 0.5” length is about $2. You will find that there is really not much need to shop around for rebar as the price depends on the cost of steel, the prices will be approximately the same no matter where you buy them.
If you are building a retaining wall you will need drainage pipes about two or three feet apart running through the wall just above ground level. Usually the pipes used are 0.75” PVC pipes with small holes drilled through to allow the water to seep through and drain away from your wall. If you don’t have these drain pipes then:
Before you start placing the pipes, find out from the permit issuing office or your local building codes office exactly how far apart the pipes need to be and how many are needed in a certain area.
If you are building a retaining wall then dig away the slope behind the wall to give you enough room to work. Cover the exposed slope with a tarpaulin and use wooden or corrugated iron sheets to help prevent he slope from caving in to the area where you are working.
As you build the wall higher and higher, gradually backfill the area behind the wall with gravel to a depth of about 18”. This will help with drainage and prevent the cinder blocks from being corroded at the base. Above the gravel you can continue to backfill using the previously excavated soil.
When you insert the drainage pipes, protect the pipes from the surrounding soil with about 4” of gravel. This will prevent the small holes in the pipes from becoming blocked by waterlogged soil. As you continue to backfill, make sure to compact the soil as you go.
Make sure the blocks are evenly spaced between the corners and work from the corners to ensure the lines are straight and level. Lay the blocks so the joints are staggered and don’t forget to allow some space for the drainage pipes to poke through the wall.
Thread the hollow blocks over the rebar and fill the hollow with concrete or mortar to hold the bar and block together. When the bar needs to be extended just add another length and bed it into the concrete fill.
Once the wall has been completed you should consider finishing off the top by using a course of cap stones. These will not only make the top edge look smooth and tidy but will also divert rain away from the top of the wall and prevent it from becoming trapped in the tiny holes and cracks and subsequently expanding and cracking the blocks when freezing weather comes.
Some people will leave their block wall uncovered except for a couple of coats of external paint, while others will consider covering the blocks with either a veneer of brick or other types of ornamental stone or will consider giving the surface a coat of stucco or render to make it look finished. Whatever you do, you should try to protect the mortar joints and cinder block from being exposed to the weather. A finish to the block wall can cost up to $300 depending on what type of finish you choose.
As said before, building a block wall is not just as simple as stacking blocks on top of each other. In order to do a good job that you can be proud of you will need some tools and something to protect you and your work area if the weather starts to rain heavily. Let’s have a look at these and learn a bit more about them.
You need somewhere dry and safe to store your tools and materials at the end of the day and also somewhere to run and shelter from the rain if it becomes a downpour. Bags of cement should not be stored in a damp place so keep them covered and preferably off the ground such as on a wooden pallet. If your cement mixer is an electrically powered one then you will need to have mains power available. Ideally this needs to be nearby and within easy reach of the work area.
Portland cement when dry is highly caustic and mortar when wet is also very caustic. Both situations can burn the skin and cause severe problems with your vision if dry cement dust blows into your eyes. You will also be cutting blocks with hammer and chisel which will also be throwing around sharp grit. Good safety equipment will prevent you from being injured in a variety of ways:
Safety glasses. Will prevent cement dust and sharp grit from blowing into your eyes.
Heavy duty leather gloves. These will prevent scratches and grazes from handling sharp cornered blocks. They will prevent cement dust and mortar from burning your skin.
Face dust mask. This will prevent you from inhaling cement dust which will burn your lungs.
Safety boots. These will protect your feet from dropped blocks.
Scaffold tower. As the wall becomes higher so it will be more difficult to continue building the wall unless you have a working platform.
Ear defenders. All machines give off unwanted noise which can damage your hearing. Concrete mixers and concrete tampers may not be particularly loud in small doses but over a long period of time the noise can have a profound effect on your hearing.
Knee pads. When working with concrete and laying blocks, you can spend a lot of time working on your knees. The ground can be hard, damp and be covered in small sharp pieces of gravel so it makes sense to protect your knees from damage.
Shovel. Both shovels and spades will be necessary for digging and for moving material. Even if you hire a mobile digging machine, you will still need shovels for the fine work of squaring off and smoothing the trench. You will need a shovel for transferring the cement and sand into the mixer prior to making mortar.
Hammer, pegs and string line. These are used to lay out the perimeter of the foundations and later to maintain a straight line when block laying.
Chisels and lump hammer. These are used to cut and groove the blocks. The hammer can also be used to tap the blocks to bring them into line and level.
Spirit levels. You will need at least two levels, preferably three of different sizes. A four foot or one meter level to keep blocks level over a long distance, a smaller boat (or torpedo) level, about six inches long to level individual blocks. The third level is about two inches long and is grooved to be able to hang along the string line to maintain the line’s level. Not only can spirit levels measure how horizontal something is but they are also equipped with bubbles which can show if something is vertical or is at forty-five degrees.
Tape measure. You will need a short pocket sized rigid metal tape measure (about ten feet or three to five meters) to measure short distances and a large waterproof cloth tape measure to measure distances along walls and foundation runs. These are about thirty or fifty feet long.
Shims. Sometimes all that is needed is to move a block a fraction of an inch for it to become level or vertical. Rather than tap the block and add more mortar, often it is better to insert a shim of known thickness to move the block. These can be strips of slate of varying thicknesses or sometimes varying thicknesses of rigid plastic.
Brooms. Not only do you need long handled brooms (both hard and soft bristle) to keep the work space clear and safe, you will also need a hand brush to clean dust and wash stone, block or brick.
Wheel barrow. These are needed to carry loads of block from one place to another as well as carrying mixed batches of mortar from the mixer to the work place.
Buckets. You will need clean buckets to carry water and to provide a place where tools can be washed. You will also need buckets to carry small amounts of mortar.
Trowels. There are various sizes and types of trowels and floats to be used for differing purposes but the essentials are a bricklaying trowel, a wooden float and a plastering trowel.
There are many factors that will affect the cost of your new cinder block wall and we are going to discuss those now:
Finished area of the wall. This is a combination of the length and height. Bear in mind that if a block wall is longer than about 12 ft or if the wall is built in a windy area, then it will need piers built within the wall. These can be described as a thicker piece of wall looking like a square pillar. It gives the wall extra stability.
The height of the wall governs how deep the foundations should be. The idea is to provide a stable foundation to prevent the wall from tilting and falling over. Therefore the higher the wall, the deeper should be the footings and therefore the more of the wall should be underground.
The shape of the wall. If the wall involves curves, corners or piers then there will be more labor involved in producing the finished object.
The type of labor used. The cost will depend on whether you use a fully trained bricklayer, a gardener, a handyman or DIY.
Surface finish. If the wall is to be covered in a render or stucco finish or have a veneer placed on after building then there is no need to be particularly neat when cleaning up the mortared joints. If however the finish is to be paint only then the pointing between the blocks needs to look good.
Other work. Depending on the purpose of the wall you may have to incorporate openings for gates, build arches, incorporate recesses for ornamental pots etc. You may have to add external wall lights to the wall. If the wall is a retaining wall then you will need to grade the slope to be a lot shallower than before. You will have to mix more cement than normal to infill the hollow blocks. You may or may not be using rebar as reinforcing for your wall. You may be building a shed or a simple garage in which case you will need to incorporate windows and a roof as well as a concrete floor.
The costs shown here are intended to be an approximate value and are indicative of the true value which will vary depending on the various factors.
|Cost of materials|
|Mortar||$5 to $7 per square foot.|
|Reinforcing bars||$0.80 per linear foot.|
|Cinder block||$1 to $3 each|
|Cost to install a cinder block wall|
|Cost per linear foot||$6 to $8|
If you decide to build your wall yourself as a DIY project then you will not have to worry about dealing with a contractor at all (remember to find out if you need a permit, this is vitally important). If, on the other hand you decide that you haven’t got the time or the skills to build your wall, you will have to hire a contractor to do the work for you.
The first question to ask yourself is which type of contractor to hire. We have already mentioned that for a non-loadbearing wall in the garden you can use a few different professionals such as a bricklayer, gardener, handyman or general contractor. They may not even have to be licensed, that requirement depends on the stipulations laid down by your local government. If however your wall is extra tall or incorporates a lot of difficult bits then it would probably be worth your while getting someone who is a fully trained and licensed bricklayer.
If you are deciding to use a contractor you should agree a contract with him that will contain all the details applicable to the job in hand. Some of the relevant questions to ask and information to find out include:
The scope of the job. Specify exactly what you want to be done. Exactly what you are paying for.
Material specifications. Specify what you want the wall to be made from and how you want it finished. Don’t forget to include the approximate dimensions.
Deadlines. When is the job to start and for how long is it expected to go on?
Payment. When is the payment due and how much is due? Is there to be a deposit?
Any changes to the contract. No matter how well a project is planned there will always be something unexpected that occurs. For example when the trench is built for the foundations you might find a higher than expected water table which requires more work to dry out the trench and fix that problem. The contract needs some way to cope with unexpected changes and how the changes will be paid for.
Insurance. Make sure the contractor has enough insurance to cover any damage that might occur to property or to people.
Certification. If the contractor is licensed, he should enclose a copy of the license and provide a means by which it can be checked.
We have already talked about the safety equipment you need to wear and why you need to wear them so we won’t go into any great detail now except to say that you must wear:
In addition to personal protective equipment you should use a scaffold tower as a work platform when the wall becomes higher than chest height.
A building site is a very exciting place for children especially with the pile of sand, the stack of blocks and holes in the ground. Unfortunately these can also cause injury to children so make sure that any little ones are excluded from the work area at all times.
We have talked today about cinder block and their uses. We have seen how cinder blocks are a good way of using the bye products from coal fired power stations and industrial furnaces so that we do not have to quarry for more aggregate for these low density blocks. We have described the different types of cinder block available as well as the cost to build a cinder block wall.
Cinder block walls are usually built in the garden as a non-load bearing wall or as a retaining wall to reduce the slope on a steep bank. They can be built by a contractor or by you as a DIY project. It is up to you and depends on your spare time and DIY skillset.
We wish you well and thank you for reading.