Learn About Paving Grouting
The material used between paving plays a vital role in the structural integrity of any paved system. In this article, we will explore the suitability of various paving jointing materials. Most importantly, we should understand that different types of pavers might be installed according to different methods, and this will have an influence on the choice of grouting material.
Grouting for small gaps
The most common type of paving installation, throughout the world, is a flexible system. In simple language, this could be described as paving with very small jointing gaps, usually filled with sand only. This method has been used since the Roman times and is what you will see in any large commercial paved areas like warehouses, residential complexes, municipal roads, etc. The engineering principle behind it, is to allow for “movement” of the pavers. This is the reason for using sand. Sand is flexible but creates interlock because of friction. Generally, after a few months, detritus makes its way into the sand filled joints and “binds” sand particles together naturally. The benefit of this is that the pavement remains flexible.
SANS 1200MJ is the national standard for the installation of flexible paving. It specifies that you sweep sand over pavers after which, you run a plate compactor over the surface, to vibrate the sand deep into the joints. In addition, sand should be swept into joints a few weeks after you start trafficking a pavement as sand will start settling in the joints. The principle is to establish and maintain joints that are completely full of sand, until it is stabilised naturally with detritus. Generally, in South Africa, we use plaster sand for paving jointing. However, in South Africa, like the rest of the world, you also find specialised paving grouting sand. It is a much better solution than generic plaster sand for various reasons, beyond the scope of this article.
Cement grouting
In many instances, property owners, want to fast track the natural stabilisation by detritus as described above. In South Africa, there is a great misconception that cement should be used between pavers, as this is hard and brings strength to the paved surface. A quick Google search will confirm that it is ONLY in South Africa where we subscribe to this misconception. When you use cement grouting between pavers, with small joints, you lose flexibility and that defies the purpose of installing pavers according to this method in the first place.
There are two major problems with cement grouting
- It stains the pavers…permanently.
- It simply doesn’t work. It starts off okay but as you traffic the pavement and expose the system to the elements there is movement, stress, expansion, and contraction, and the cement grouting starts breaking out. It is also impossible to successfully re-fill the joints with cement grouting.
Joint stabilising sealants
The best possible option when you wish to stabilise sand between pavers and prevent it from washing out etc, is to use a Joint Stabilising Paving Sealant. These are specialised, urethane-based sealants, engineered to bind sand between pavers while maintaining complete flexibility. These stabilisers are fool-proof and used in specialised applications all over the world. Resiblock is a brand available in South Africa.
Polymeric sand
Another option is to use sand mixed with special polymers. This method became very popular in the USA and eventually made its way to South Africa. It is simple to install. Sweep the sand mixture over joints and plate compact as you would do with normal sand. Then you use a leave blower to remove fine polymer dust from the pavement…or it might stain your pavers and apply a fine water mist. This will result in hardened joints. The only drawback is that polymeric sand does not last as long as the specialised joint stabilisers described above, but it is more cost effective in the short term.
Romex NP sand
Romex is a specialist German manufacturer of paving grouting. Some of their products are available in South Africa. They sell a product called NP sand which is installed in a similar way as Polymeric sand described above, but the active binding agent is not polymer based. This offers three major advantages. The product lasts much longer than conventional Polymeric sand. Secondly, it is self-repairing. Should small cracks start forming, contact with water “repairs” and “revives” the grouting material. Lastly, it is highly flexible. The disadvantage is that it costs more than conventional polymeric sand.
Grouting in large gaps
The second type of paving installation is where jointing gaps are large, and pavers are installed on a mortar screed. We generally call these pavers “Flagstones”. Grouting gaps are also bigger than flexible pavers described above. These gaps are generally 5mm or more, in width.
In South Africa, cement-based grouting is generally used for these applications. Unfortunately, it never works in the long term. The problem is that pavers are installed outdoors and expands and contracts. Cement grouting simply can’t stand up to these stresses. Eventually it cracks and breaks out.
Specialised resin grouts for large gaps
The only jointing material for large gaps that can stand the test of time and withstand the elements, is a range of specialised resin-based grouts. Again, manufactured by Romex , these products are imported from Germany and are not cheap. They are however guaranteed to last a lifetime.
Generally, pavers with larger gaps, (flagstones) are used for outdoor living spaces. It is simply not worth-while using a grouting material that might ruin your outdoor living experience. Who would want the floor in their lounge to start failing after two years???
