How block paving sealers really work

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It has become almost an annual ritual for thousands of us – cleaning the block paving. Over the winter time especially our driveways and patios pick up dirt from car tyres, wind-blown dust and autumn leaves. Cleaning up this lovely mess is made all the more challenging because this dirt tends to gather in the “V” grooves between the blocks attracting weeds and moss growth. This dirty job is best tackled with plenty of enthusiasm and a good pressure washer, with an output pressure of 2500 psi and a “rotary jet” nozzle, also referred to as a “turbo” nozzle. This will usually do a very good job of brightening up even the dirtiest paving.
It is at this point in the process that most people’s thoughts turn to “why is it faded and how can I make this job easier for next time??? Which brings us onto the subject of “paving sealers”….Are they any good? Which one should I choose? And where can I get the best deal?

So, do they work and do I really need a sealer at all?

The answer is that it depends on what you are looking for…. Block paving fades as it weathers and ages, so the right sealer can make a huge difference to the appearance of your driveway or patio, bringing out the colour and enhancing the overall appearance. A good quality sealer will also protect against oil stains and resist de-icing salts which are very corrosive to concrete block paving. However, be wary of sellers telling you that their sealer will stop weeds coming back permanently by sealing the sand joints. Whilst most sealers will bind the sand joints to some extent, it is not desirable to seal them completely as the concept of block paving is that it partially drains through the sand joints.

There are 3 main “types” of paving sealers;

Water Based Acrylic Sealers
These will typically come in a 5 litre plastic container and fall into the cheaper end of the price spectrum. Being water based they are easy to apply by brush or roller and don’t have any of the solvent odours associated with polyurethanes and oil based acrylics. However, although they have improved greatly in recent years they still do not have the durability of the oil based acrylics and polyurethanes.

Oil Based Acrylic Sealers
Long favoured by professional applicators and usually supplied in 5L or 25L tin containers, these are also easy to apply by brush roller and even spray (if you have the professional equipment). They have better durability than their water based cousins but you need to avoid moisture contamination from random rain showers. Most give a pleasing satin finish which mimics the appearance of wet paving and brings out the original colour.

Polyurethane Sealers
Also well regarded by professional applicators “Polyurethanes” are undoubtedly the most durable variety of paving protection as well as the most expensive. However, DIY applicators especially beware as there are drawbacks. Application must be strictly according to the manufacturer’s guidelines - beware of moisture contamination as unlike oil based acrylics there is no chemical method to remove the staining.

So where do I go to get the best deal?
An average 2 car driveway is around 50 to 60 square metres and paving sealers usually cover 5 sq m per litre, so for two coats you will need 20 to 25 litres. Unfortunately most DIY stores don’t stock the big drums so you will pay more by buying multiple 5L containers. Look online for known manufacturers selling direct and avoid “white tins” as that usually tells you that they are small volume producers.
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