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Rigid Construction for Block Paving

By: Chris Hogan MSc - Updated: 22 Mar 2012 | comments*Discuss
 
Blocks Driveway Rigid Paving Setts Cubes

Block paving, the sort that’s made from smaller, traditional-sized blocks rather than the larger flagstone sized blocks, is usually laid in one of two ways, rigid or flexible. In the past, when roads and streets were made this way in many parts of the United Kingdom, the laying method would have been of the flexible kind.

Rigid versus flexible

But in more recent decades the trend has been toward rigid construction, where the blocks (variously known as setts or cubes around the country) are laid on a concrete bed. Flexible bedding isn’t, of course, flexible in the way that rubber is, but it is more flexible than rigid paving. The level of movement allowed by flexible construction can make it more suitable for areas where a little settlement can be expected.

But for most driveways the rigid construction is simple to lay and more than adequate. The exact specification for the various levels of the driveway will depend on the amount of traffic the driveway can expect, but we will give guidelines for a lightly trafficked driveway, two to three cars in length.

The different layers

The laying principles of a rigid construction driveway are simple, hence it’s popularity in the modern era. Instead of a number of different layers of hardcore, sub-grade and bedding, all you need is a concrete bedding layer about four inches deep to bed the blocks into.

This means you only have to dig the channel for the driveway to four inches plus the depth of the blocks you are going to lay. The channel should also be two or three inches wider than the actual drive to give you room to manoeuvre the blocks at the edges. Don’t forget to allow for an edging strip as well.

Clear any weeds and consider putting some weed-killer down if they are particularly bad. Once the bottom of the channel has been compacted, fill any significant depressions with crushed hardcore and compact again.

Edging – if you fancy it

If you are thinking of edging your driveway then build that in before you start adding the bedding layer. It isn’t strictly essential to use edging on a rigid construction block driveway, as the blocks should be held securely in place by the bedding layer. But it may help the driveway to last longer, in particular preventing chipping of the blocks at the extreme edges.

It can also look better too, although it depends what’s at the edges of your driveway, grass, edged beds, fencing or perhaps something else? There are a couple of articles on edging for the various different driveway types on this site so take a look at some of those to help you decide.

Of course you need to measure the width of the driveway site very accurately and lay your blocks very accurately to make this all come together properly. If you are using reclaimed blocks which are irregular in size, you will need to plan very carefully as you reach the edges, selecting a combination of blocks that will allow you to reach the edge on each row without it looking odd.

Bedding layer

The bedding layer is a concrete mix that has a cement portion, just enough so that it stays flexible for longer, allowing you to lay the blocks, then sets hard, but not rock hard. This is known as a ‘lean mix’ and various websites, particularly concrete manufacturers, offer calculators which will tell you the right ratios and the amounts you will need for the area of your driveway.

There needs to be a camber in most driveways so build that into the bedding layer. The easiest way is to cut a template of plywood that curves the correct amount then use it to check the profile of the bedding layer as you go. You can use the same template later to check the profile of the blocks themselves and retain the integrity of the camber.

Block laying and jointing

Lay the blocks, setts, cubes, whatever it is you are using, in the pattern you’ve decided on, taking great care to keep joints as consistent as possible. You will also need to joint the blocks to keep them in place and set properly.

We have articles that cover the laying of the blocks in more detail and numerous articles on the different types of jointing available for block paving, so refer to those to help you make your choices and do the job when the time comes.

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