Sealing Stone
FAQ quicklinks
1. Do I have to seal flooring products?
2. What type of sealant should I use?
3. How often do I need to seal?
4. Sealing pool surrounds?
1. Do I have to seal flooring products?
Natural stone is tough and very durable but may need to be sealed depending on how it is used. Sealing is not always recommended for outside areas that are frequently inundated - it depend on the type of stone used and its environment. In general though, sealing is recommended anytime the stone is subjected to chemical (coffee, wine, salt) or biological (leaves, food) staining.
In other instances sealing may be a good option as it can enhance colours and make the surface easier to clean. In a kitchen or outdoor BBQ for instance, sealing is recommended as it will help prevent discolouration or staining caused by spillages.
If sealing, make sure the sealant is appropriate for the type of stone being used eg. sealants designed for marble may not be suitable for sandstone.
2. What type of sealant should I use?
There are different types of sealing products to give different finishes and you need to get good advice to ensure you get a product that suits your purpose. Penetrating sealer leaves the stone looking natural; while acrylic sealers highlight colours within the stone.
3. How often do I need to seal?
It is recommended that at least two thin applications of a good quality sealant be applied initially with follow-up treatments applied as needed depending on traffic and exposure to the elements. The initial applications need to be kept thin so the sealant doesn’t puddle in grout joints.
Ensure that the surface has been thoroughly cleaned to remove all dirt and grime before applying the first coat of sealer. Sweep and re-clean the surface with a neutral cleaner before applying subsequent coats.
After re-sealing your natural stone will look new again!
4. Sealing pool surrounds?
Salts from swimming pools can cause some types of stone to exfoliate so the choice of stone for use around swimming pools is critically important. The best indicator of how well a stone will perform in a pool environment is its test result for resistance to salt attack (see test results section).
There are big differences in the ability of stone to resist salt attack. Grey Gum & Sofala quartzites are very dense, durable stones with low water absorption characteristics and good salt resistance. Both are suitable for use around pools but should be sealed as a precaution.
Sandstone is extremely popular for use around pools but they are highly variable in porosity, density, water absorption and resistance to salt attack. Sandstone sourced from Rajasthan in India are far more dense than Sydney sandstone; tests reveal better potential durability. Some types of sandstone (eg Coolum) are not recommended for use around pools. It would be sensible to thoroughly seal sandstone with a water based penetrating sealer even if they have a high rating for resistance to salt attack.
Pool coping that is likely to be frequently inundated by splashing water should be sealed at least three times on all sides prior to fixing and re-sealed annually.
Make sure that any stone used as pool coping is thoroughly sealed under the exposed lip as any salt laden moisture that gains access at this point will be held in the stone. Eventually the water component will escape through the barrier created by the sealer just under the top surface of the stone, but the salt will remain.
Salt will cause damage to any hard surface not just stone. It will reek havoc with concrete if it can gain access - water is just its means of transport! Water carries the salt into the minute pores of the hard surface and eventually the water evaporates leaving salt in crystal form. If the process is repeated the salt crystals get larger creating a force capable of damaging the structure of its host. The symptoms of structural damage are pitting, flaking and spalling.
Most pool aprons are a battle ground of physical (high traffic) and chemical (salt) forces and that is why annual re-sealing is desirable.