Home > Concrete & Tarmac > Putting Expansion Joints In Concrete Drives

Putting Expansion Joints In Concrete Drives

By: Chris Hogan MSc - Updated: 10 Apr 2017 | comments*Discuss
Expansion Joint Expansion Joints

A lot of people reading this will be thinking, "What, joints in concrete? Doesn't concrete just get poured out?" They'll be right, to an extent, but if you remember any really large, flat Concrete Surface you've seen, there will have been black lines across it every so often. Yes, those lines mark where the expansion joints are.

The Need For Expansion Joints

Concrete sets very hard, more so than many other popular drive surfaces. But like most materials it also expands and contracts as it heats up and cools down. Combine that strength with this expansion and it's easy to see why Concrete Cracks, and why you need to put in an expansion joint in a large slab.

There's aren't that many driveways that will need expansion joints. A slab can be about 20ft square (6m square) before it will need an expansion joint, but it's not only size that matters. As well as preventing the slab from simply pulling itself apart, expansion joints protect fittings, like drain access covers and adjacent walls, from being broken by the forces that the slab exerts as it expands and contracts.

Components Of An Expansion Joint

Expansion joints are gaps between sections of poured concrete filled with a material that allows movement in the gap (more on this later). The top edges of the two slabs will often be chamfered to prevent them from cracking (spalling) and one or both sides will have a recess for the top inch or two.

This recess is filled with a flexible sealant to prevent debris and water getting into the gap. It's this flexible cover that gives rise to the black lines, as traditionally this would have been bitumen. These days bitumen isn’t used so much and it's more common to employ a resin-based compound that's applied cold with a curing agent mixed in.

Filling The Gap

On a very large concrete surface dowelled joints are used. The steel dowels are inserted into one side of the joint with recesses in the opposing face. As the concrete expands and contracts the dowels slide in and out. The gap between the slabs will also be filled with a flexible material, often a board made of fibre.

It might seem odd filling a gap that's meant to allow movement, but the movement is small and slow. The board can cope with it as long as it is the right width for the gap, usually between 0.5-1.5in (about 1.5-4cm). The board prevents too much dirt and water getting into the gap which it inevitably would, even with the sealant at the top.

Get Expert Help For Your Drive

If this all sounds a bit complex, then that's because it is. Creating the right gap widths and filling them with the correct material is not really a job for the amateur. It's far better to get a contractor who can demonstrate that they have previously put expansion joints into a concrete drive.

If you are intent on laying a large or long concrete driveway yourself, you really should consult a structural engineer with the relevant experience before starting the project.

You might also like...
Share Your Story, Join the Discussion or Seek Advice..
Why not be the first to leave a comment for discussion, ask for advice or share your story...

If you'd like to ask a question one of our experts (workload permitting) or a helpful reader hopefully can help you... We also love comments and interesting stories

(never shown)
(never shown)
(never shown)
(never shown)
Enter word:
Latest Comments
  • diddy
    Re: Gravel Driveways: Advantages and Disadvantages
    Have just had a loose gravel driveway laid and already finding it hugely inconvenient for wheeling anything…
    16 November 2017
  • Edd
    Re: Planning Permission for Driveways
    My house is not on the same level as the street, it is down from the road and path. I want to build a driveway, but if I…
    6 November 2017
  • Saxa
    Re: Resin Bound Driveway Surfacing
    Hi, had a resin bound drive layed last May, and we were very pleased with it until now. What we didn't know then was that…
    30 October 2017
  • Colin
    Re: Resin Bound Driveway Surfacing
    Hi. Can bound aggregate be laid on an established concrete drive which is damp or wet? My contractor says it can though the…
    20 October 2017
  • John
    Re: The Art of Laying Tarmac
    We had a new ditch dug earlier in the year which holds a new drain, gas, water and electricity pipework, which goes to a garage…
    17 October 2017
  • Helper
    Re: Resin Bound Driveway Surfacing
    @Safetyfirst Without going in to the drainage, planning and use of a flexible system details, as a manufacturer we would not…
    15 October 2017
  • Helper
    Re: Resin Bound Driveway Surfacing
    @Thomo5949 Resin bound or bonded surfaces are not suitable for this application. Whilst they can be installed directly onto a…
    15 October 2017
  • Helper
    Re: Resin Bound Driveway Surfacing
    @jock No this is not normal. Trowel marks are either the result of an unskilled installer, the over use of solvents to lubricate…
    15 October 2017
  • Ruth
    Re: Planning Permission for Driveways
    Hi I need advice. We want to pave our driveway. Our rainwater directed to border. Do we need any permission? Just one thing…
    11 October 2017
  • gilly
    Re: Patterned and Textured Concrete
    just looking to see how much for a new driveway.patterned concrete
    11 October 2017
Further Reading...
Our Most Popular...
Add to my Yahoo!
Add to Google
Stumble this
Add to Twitter
Add To Facebook
RSS feed
You should seek independent professional advice before acting upon any information on the DrivewayExpert website. Please read our Disclaimer.