Block Paving Sealer - Info

Solvent Based v Water Based and Polyurethane Sealers.

The vast majority of contractors will choose to use a solvent based acrylic sealer for block paving rather than a waterbased sealer (or a polyurethane) mainly because they are significantly more user friendly. It is also much easier for a homeowner to use a solvent based block paving sealer to refurbish their paved areas.

Polyurethanes sealers

Are expensive, but they are very hardwearing and very resistant to chemicals and solvents. They are ideal for certain applications such as on petrol forecourts, where the surface would be subjected to petrol and diesel spillages. They are generally regarded ‘over spec’ for the average area of paving and in particular for domestic areas of paving.

Waterbased sealers

Are less durable and are not so chemical resistant, however can be used for domestic or light commercial applications. The resultant sealed surface is slightly opaque, unlike urethanes or solvent based acrylics (which are clear) and the natural colour of the paving is not enhanced to the same degree.  

The significant negatives to using a urethane or a water based sealer are when either a) something goes wrong (remember we are sealing exterior areas and subjected to various weather conditions) or b) when an area would benefit from refurbishment.

Polyurethane sealers 

Are not affected by solvents, such as xylene and therefore ‘just melting’ the defective sealed layer and allowing it to reset is not an alternative. Any problem areas would need to be totally removed using aggressive chemicals or by mechanical means such as shot blasting, prior to resealing the area. In the case of a reseal, to rejuvenate an area, the sealed surface must have a mechanical key in order to ensure a good bond between the original layer and the new layer. This entails significant additional work and also, the sealed surface will develop  a thicker layer which can make the paved area less authentic and more artificial in most instances (tiles, would perhaps be an exception to this aesthetic observation). Also, thicker layers of sealer reduce the skid resistance values of paved areas. An important consideration for external areas.

Water based sealers

Are partially, but not totally affected by solvents. The solvent partially melts (and damages) the sealed layer however it does not change back to its original finish. The damaged layer would need to be removed before it is resealed with any type of sealer. In order to fix a damaged area, the original layer needs to be totally removed before the area is resealed. For future reseals, or to rejuvenate an area, the original layer requires a mechanical key, just like a urethane, and just like a urethane, a thicker layer is formed on the surface, making the area less authentic and reduces skid resistance values.

Regarding refurbishment, after two or three re-applications, both these types of sealer would generally be removed in order to ‘start from scratch’ for any other future refurbishment work.

Solvent based acrylic sealers

Produce a totally clear film, therefore enhancing the sealed surface to maximum effect. Should there be a problem with the sealed surface, xylene (solvent) is applied to the area, the sealed layer is melted, it resets and the area is rectified. It may need a light application of sealer in certain places and if it does, bonding is not a concern as a new layer of sealer will always bond to an existing layer of sealer as the new layer will ‘melt’ the exiting layer and the layer will ‘become one’.      

Refurbishment is equally easy. The sealed surface is simply melted using just xylene to bring it back to new, and if an area has worn in places, it can easily be re-coated with another layer of solvent based sealer, which will bond totally to the underlying layer. If required, areas that have been sealed with a solvent based acrylic sealer can easily be kept in pristine condition.


Although all three types of block paving sealer can be used successfully to seal areas of external paving, listed below are the main positive and negatives of each type of block paving sealer.


  • Hardwearing, highly chemical resistant.
  • Expensive, problematic to resolve defects, problematic to refurbish or reseal.

Water Based Acrylics

  • Solvent free, no smell, environmentally friendly.
  • Opaque film, problematic to resolve defects, problematic to refurbish or reseal.

Solvent Based Acrylics

  • Totally clear film, easy to solve defects, easy to refurbish or reseal
  • Smell, hazardous material.

Although we can supply all three different types of sealer we would recommend acrylic sealers for the reasons above, for further information on any type of block paving sealer Smartseal on 01268 722500 or fill in our online form