Defects in Stonework
Stone is a natural yet complex material. There seems to be a lots of misconception surrounding stone that is on the market these days and it is important to at least understand the fundamentals. Source stone from reputable suppliers who have come from the industry. Ask if they have mined stone, processed stone or if they are just traders. Probe away as it may save you a lot of hard earned money, stress and heartache along the way.
Stones all vary in compositions and are do not all react in the same manner. For example not all sandstones in Australia have the same compressive strength and not all sandstones are prone to salt attack. In fact, there are some sandstones found in NSW which have very minimal salt attack results. Not all stones absorb at the same rate and so forth. We can get in to the nitty gritty but for the purpose of keeping this simple, we will provide just some basic information.
The significance of pore structure in stone is highly important. Pore structure is significant because it affects the amount of water entering and moving through the stone. Also, salts that may damage the stone can be transported by water and accumulate in the pores. The critical factor is not the total amount of space created by the pores but how they are structured.
Stones with low porosity will not allow much water penetration and are therefore less likely to suffer salt and/or frost attack. Stones with low porosity are therefore generally more durable.
Stones with high porosity will allow more water in but, if the pores are large, the water will tend to be able to evaporate reasonably quickly. However, if there is a large network of fine pores, capillary action will be high, but evaporation will be relatively low. In addition, a stone with large pores is less likely to suffer salt damage than one with small pores. This is because the larger space is more likely to be able to accommodate the expansion pressures of salt crystallization.
Incorrect bedding. All too often we see stone delaminating in particular stone sourced from overseas as there does not seem to be any emphasis placed on incorrect bedding. Basically this means that the stone will delaminate prematurely as sedimentary stone needs to be cut or split with or against the grain depending on the intended final use. For example, walling stone needs to be split horizontally opposed to flooring which is to be cut or split vertically as extracted from the ground.
To give stone the best possible means of protection. It is always recommended to seal the stone. There are a lot of sealers on the market but we have always stood by the Aquamix range and found it to be the most effective. Contaminants such as acid rain, bird droppings, insects and pollution are just some to name a few which can have an affect on stone so it is always good practice to seal the stone upon completion.
As with brickwork, an inappropriate mortar mix can cause problems in both the mortar and the stone itself. The main problem is usually related to having too strong a mortar. Because a strong (dense) mortar allows less evaporation, any moisture in the wall will have to evaporate through the stone. This may increase the likelihood and severity of salt related defects.
Additionally, stronger mortars are relatively brittle and may be susceptible to shrinkage cracking. This may increase the likelihood of rain penetration, which in turn may increase the potential for salt related defects and frost attack.
Aussietecture proudly owns and operates several quarries and factories and the owners have over 40 years combined experience in dealing with stones. Our experience and knowledge is your peace of mind. Talk to us about our experienced installers who can assist which the same kind of service we provide as suppliers.