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How to Compare Paving Installations

On the face of it, all block paving installations may appear the same. However, the foundations tell a different story, one which greatly affects the lifetime, quality and appearance of paving. This article explains the different approaches to the installation of block paving and what to look out for to ensure that your paving is fit for the purpose and will remain in a good condition for years to come.

From The Surface

The drawing below shows a block paved driveway as viewed from above.

The hatched area on either side of the sketch is called the haunch, this should come at least two thirds of the way up the side of the BPER (block paving as edge restraint) to retain it in position.

Paving view from the top

Regardless of the construction method used, all of the examples would look like this when viewed from the top. The laying pattern used in this illustration is a 90 degree herringbone pattern.

Foundations

It is in the foundations where we see different stories told. The diagrams of each method below shows a cross-section of the paving foundations, as if viewed from the side.

Method A below is our own approach to laying block paving - one which is of a high specification and will guarantee your driveway or patio for years to come.

We then explain alternative methods, each one subsequently less scrupulous.

Method A -  A Correct Installation

This diagram shows a driveway when it has been constructed to our specification.

Method A - A Correct Paving Installation

The method of construction is as follows:

  • There is a complete excavation of the existing surface to a depth of 300mm
  • A deep concrete footing is installed (diagonal lines). This prevents any of the construction layers from moving laterally
  • The BPER is set upon the concrete
  • An underlying geo-textile membrane is then laid to prevent layers from above mixing with the sub soil in very wet conditions
  • An 8" 'Type 1' sub-base layer, which is a mixture of stones, is installed. Its purpose is to spread evenly the load of the paving and aid drainage. This is laid in two layers, each individually compacted, to ensure that the sub-base is fully compacted prior to installation of the surface layers
  • A sharp sand is then laid to create a flat surface area. This is achieved using ‘screeding bars’ and a strait edge
  • The blocks are laid in the pattern as chosen by the client
  • Gaps are filled by cutting blocks accurately using a diamond-cutting blade prior to initial compaction
  • Finally, Kiln-dried sand is brushed over the area until all of the joints are filled and the driveway is compacted again.

Method B

The diagram below shows an installation similar to the one above, but with a number of corners cut.

Method B

Characteristics include:

  • A less deep excavation of 260mm
  • No underlying membrane, the lack of which will cause the sub-base to mix with the underlying soil in wet conditions
  • A thinner 6" sub-base is installed prior to concrete footing. This means it will move laterally with use and over time, which in turn will cause gaps to appear between the block. This may be mitigated if a 600mm margin of sub-base has been laid around the driveway, however if the paving sinks it would be very difficult to relay if the BPER has moved, even just a little.

This method requires less excavation, muck away and concrete to install the BPER on, it would also take slightly less time to construct because less concrete would be mixed on site, but this has been achieved at the expense of longevity.

Method C

This method is similar to B, but is progressively worse.

Method C

Characteristics include:

  • A shallow 200mm excavation
  • As per B, no underlying membrane
  • A 4" sub-base is installed, half the depth of Method A, and as with Method B, no restraining concrete footing
  • The BPER is laid directly on the sand and only retained by a concrete haunch. This driveway will start to fail quite quickly, water will freeze around the haunch causing it to fail and the blocks will very quickly start to move apart allowing weeds to establish.

This method requires even less excavation, muck away and hardly any concrete. This approach will significantly reduce time and costs, but at great expense to the lifetime and quality of the installation.

Method D

This is the worst scenario we have come across.

Characteristics include:

  • Sand has been spread directly over the existing driveway, no excavation.
  • The blocks have been installed and the haunched with concrete

As no excavation has been done, the surface is likely to fail very quickly. Block paving should always be installed on a permeable surface. Even if the existing tarmac is solid and the levels are acceptable so that the new finished level does not breach the damp course, the contractor should still remove the impermeable tarmac or concrete layer - otherwise the sand layer becomes so wet that it turns into a jelly-like substance.

Laying the block paving is around 30% of the time taken to complete a driveway as in Method A, so with no excavation or muck away and a negligible amount of concrete, an installation based on this method would be massively cheaper - but at what real expense?

Choosing a Firm Foundation

We build to our own specification (Method A) because it gives our customers the assurance of a long lasting capital investment. It also gives us the confidence to offer a guarantee of up to 10 years with a couple of maintenance visits, and will provide you with a driveway or patio that you can enjoy, trust and be proud of for years to come.

When comparing quotations for a paving installation, ask your paving contractor to describe the method they use, and compare it with the methods described here.

If you have any doubts or questions, we are always on hand to answer them.

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Many of our neighbours have commented on the quality and speed of your service, and the difference the materials and design you used has made to enhance the appearance of our property.

Mr Williams, Dale House Lane, Kenilworth

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176 Kenilworth Road, Balsall Common, Coventry, CV7 7EW, Tel 01676 535 675
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