Link or Stacker Retaining Wall Blocks That You Can Build without Mortar/Cement

They stack on top of each other and do not require any mortar or cement joins. This obviously makes construction much easier and means that the home handyman can produce a quality outcome. In fact, there have been some comparisons made with good old fashioned “Lego” where once the bottom course is laid, the blocks just click together!

• If a mistake is made… as there is no mortar, you can just dismantle it and start again.

• In most cases, the block weights are  less than 20kg each making installation easy and possible for most people.

• Being a manufactured product, their sizing and uniformity is very consistent, again making installation a breeze.

• Depending on the style chosen, they can be used in straight or curved walls and in many cases can do right angled corners too.

• Given the variety of styles and colours available, they can blend in with any type or style of landscaping project.

• There are styles that build a vertical wall and some that slope backwards into the bank to give more strength and there is even a style that is hollow, allowing you to fill them with soil and plant them out … giving a rockery type appearance.

• There are quite often special money saving offers running on one form of block or another which means, this type of wall can be built very economically.

Things to be cautious of when using Link Retaining Wall Blocks

• It is a good idea to read the manufacturer’s guidelines as to the capabilities and specifications of the block. Some of the biggest problems arise when a block is used for an application that it is not designed to handle, e.g. a specified height or right angled corners, etc.

• In spite of modern technology, all these blocks have the potential to fade to varying degrees over the years and depending on their location, they may well succumb to some mould growth on the surface. These are processes that happen naturally and cannot be avoided, however, they do respond well when cleaned with a gurney or high pressure spray.

• If the bottom course is not laid level and carefully, this can result in the wall appearing uneven, as each course will follow the pattern of the one below. Ensure extra care is taken laying the bottom layer and have a spirit level available at all times! See DIY Video

Consider the stability of the ground when planning the footing below the wall. Some brochures recommend compacted road base which can be fine for small walls (say around 50mm) but on higher walls, up to 1m, the use of concrete (a mix of Concrete Blend and Cement) is a much better idea as it not only strengthens the wall base a great deal but also ensures that each level stays exactly level for the life of the wall.

Timber Retaining Walls

All the timber sold at Centenary is treated, with most using Copper Chrome and Arsenic (CCA), which protects the timber from both fungal attack (rotting) and insect attack (termites). Copper is the fungicide, Chrome, the insecticide, and Arsenic is the fixing agent that holds the chemicals in the wood.

Over recent years there have been growing concerns about the safety of such chemicals in timber, and Europe and America have moved away from such treatments. In Queensland, CCA treated timber is now not allowed to be used in schools or playgrounds, but can still be used in general landscaping. Slowly there is a move towards "ACQ" treated timber which we also supply.

Levels of treatment

There are different amounts of treatment put into the wood, depending on what it is being used for and it is very important that the timber you buy is treated to the level required for the job at hand. When building a retaining wall, the timber will be in contact with the ground and therefore has to have a treatment grading of “H4”. The gradings of timber are:

• H3 ….  Exterior use but above ground (e.g. fence rails and palings, pergolas, etc.)

• H4 ….  Exterior use in ground (e.g. retaining walls and fence posts)

• H5 ….  In contact with water (e.g. jetty or pontoon)

A second type of grading that is used on timber is related to its strength and while this is especially important in the building industry, it is also important to be mindful of when landscaping. The strength of a piece of timber is the "F" rating. Most landscape hardwood is graded "F7", while most pine is graded "F5". High quality building grade timber (which we do not sell) is generally around "F14". For most domestic retaining walls, the "F5" Pine is more than adequate, although, a wall over one metre tall will require your local government Council approval and more than likely will require an engineered drawing. (Check with your particular Council for heights that need approval and engineering plans.)

The timber we sell that can be used in Retaining walls, can be divided into the following groups:

Treated Hardwood Sleepers

Our sleepers are taken from a variety of hardwood species including Ironbark, Grey Gum, Spotted Gum and Yellow Stringer. You have to remember that when buying hardwood, it will always be of poorer quality than that used in the building industry, and is termed “Landscape Grade”. For example, a good and satisfactory sleeper only has to have one good face and one good square side to be considered OK. This is an important consideration when deciding on the construction method you will be choosing for your wall and it is a good idea to come and see the actual sleepers here in our yard before buying them. We consider them to be of a higher quality than what is usually available at a lower price. We also can access cheaper sleepers but they cause too many problems for our customers.

Whilst the hardwood is treated, it comes with no guarantee against termites or fungal attack, primarily because during the treatment process, the chemicals only penetrate the outside couple of millimetres (because the wood is dense and “hard”). This means that if a crack opens up in the timber, or it is cut, untreated timber becomes exposed. So the treatment of hardwood will only minimize the risk of attack, not stop it altogether. Hardwood sleepers are treated to the "H4" level.

Treated Pine Sleepers

Most of the pine timber we sell is harvested from the State Forests near the Glasshouse Mountains, although some is imported from New Zealand. The range of sizes in Pine is different to those in hardwood so be careful.  The overall appearance and quality in pine sleepers is much better. Hardwood is mainly dark brown in colour, with pine being much lighter with a green tinge. Some customers know that this green colour has something to do with the treatment (it is actually from the Copper) and believe that unless the sleeper is green in colour, it hasn’t been treated properly. You can be reassured that ALL timber is treated, and that the extra green is generally when that pack is at the base of the treatment tank and sits in the copper residue a little longer. With all pine timber, you will find a stamp on the end of it that shows when and where it was treated, and this is our assurance that the process has been followed correctly.

Unlike the hardwood, pine timber comes with a 40-year guarantee against termite and fungal attack, because the timber is not as dense as hardwood, so that when it is treated under pressure, the chemicals can penetrate all the way through the timber thus giving it complete protection. This guarantee does not however mean that the piece of wood will always look perfect. It will still age, weather in the sun and potentially crack and bow just like any other piece of wood exposed to the elements. Obviously, this can be minimized by applying wood stains or other protecting paints/oils. Pine sleepers are treated to the in ground "H4" level.

If you are looking to build a vegetable garden, or sandpit …. And are concerned about the "CCA Treatment", then we now have in stock a range of "ACQ" Treated sleepers. These have a slightly darker appearance and are a little more expensive than the "CCA" Sleepers.

Treated Pine Logs

We carry a large range of pine logs in lengths, diameters and different profiles (see the price guide) and they come with the same guarantees as the pine sleepers. Stock availability is also good, except with the odd sizes, but again, check the price guide and it will tell you what sizes we have to order in. Logs are treated to the in ground "H4" level.

The logs are just as effective as sleepers, they just provide a different look to the wall. In fact as of March 2011, we have been able to reduce the price on logs by up to 25% …. And this is not just a temporary special but a new low price that makes them a very competitive alternative.

When comparing pine and hardwood timber, consider the following:

• Pine will last longer and comes with a 40-year guarantee

• Pine is lighter and easier to cut and drill

• Pine is generally better looking and there are fewer rejects

• Pine is from plantation forests, not old growth hardwood

• Hardwood is structurally stronger... but how strong do you need the structure to be?

• Hardwood is slightly cheaper initially.

Rock Walls

If you are considering building a Rock Wall, and it is going to be substantial, over one meter or even more, it is advisable that you consult a professional. Give us a call at Centenary and we will pass on some contact details of a Contractor who could visit your home and advise as to the best strategy.

If you are considering building a Rock Wall, and it is going to be substantial, over one metre or even more, it is advisable that you consult a professional. Give us a call at Centenary and we will pass on some contact details of a Contractor who could visit your home and advise as to the best strategy.

If the effect you are looking for is more of a rockery type finish or a smaller wall below one metre, then we have some “Man Handleable” sized rocks for you to choose from (see the Rock & Boulder Shop).

Once you have had a look at the types of rock available, browse through some of the websites below for extra tips on putting a rock wall together yourself:

• Build a Dry Stack Retaining Rock Wall
  

• Rock Retaining Wall - Ask the Builder

• Retaining Walls - Building Stone Retaining Walls - Tutorial on building retaining walls out of natural stone, three feet in height or less. Building retaining walls from natural stone without.

Concrete Sleepers

I guess here we are stating the obvious when we say that you can now get the look of a timber retaining wall while using concrete. This avoids all the inherent problems with using timber: The concrete sleepers do not bow or they crack; don’t twist; and don’t weather as a pine or hardwood wall would. They also will never rot!

There are three different types available which can be viewed in the Concrete Sleeper Section. There is a rustic, charcoal look (similar to old railway sleepers); a textured dark brown one (more similar to normal sleepers) and a plain concrete finish which is more economical.

Be mindful that these sleepers can be quite heavy and are not that easy to cut ( as they are reinforced). They are therefore not that flexible and while they are available in a variety of sizes, they are designed to work in those lengths and only those lengths. These can be a drawback and frustrating when using them in your structure.

How Important Is Drainage??

The short and simple answer is …. EXTREMELY  IMPORTANT!!!

Whenever we build a wall, be it retaining a stable “cut” in the land or holding back fill,  the effort we put into the drainage behind the wall is crucial to the long term success of the wall itself. By erecting a vertical or near vertical structure at a point where the land changes in height, there is  the potential for it to become a “Dam Wall”. If this occurs, water will be trapped behind the wall where it builds up pressure on the supports and in some cases results in the wall failing or bring pushed over.

In our DIY Video, there is a strong emphasis on the drainage material used behind the wall being built. The whole reason for the drainage is that during heavy rain or extended wet periods, water does NOT collect behind the wall and instead has a way to “escape”.  This is done by placing an "Ag Pipe" at the base of the wall (behind it) and then covering this with Drainage Gravel. The quantity of gravel used will vary, depending on the height of the wall and the amount of water runoff expected, but as a general rule, the more gravel used the better.

One thing to avoid at all costs, is lining the back of the retaining wall with plastic as this will indeed result in water being held behind the wall. If you are concerned about dirt seeping through the joints in the wall, then you can line the wall with a filter cloth called "Geofabric" (Bidim) as this will let the clean water drain through and hold back the dirt. See DIY Video.

When designing your wall, check the manufacturers’ brochures or the DIY videos on our website to get the full story on the importance of drainage.