Question
Hello Sean-
I want to create a simple 4"slab type concrete walkway around the perimeter of my house.  I understand I need expansion joint every few feet(3'-4'??) but do not know exactly how to do it.
I have done plenty of foundations through work but this will be my own project.
Please advice.  I can also be reach in person via my wife's cell @ .
Thank you for your prompt attention to this request.
Shaun

Answer
You will need an expansion joint about every 30 feet and a 'control' joint about every 5 or 6 feet. Typically you would space a control joint about equal to or slightly further apart than the width of the walk. So if you have a five foot wide walk, you place a control joint about every 5 or 6 feet until you reach 30 feet then you do an expansion joint. Sometimes it is best to measure the distance to the end of a run and then find some measurement that will provide equal spacing. It may be something odd like 74" or 59". That way you don't end up with one odd size panel at the end.
An expansion joint is either a piece of wood 1/2 to 1" thick placed between the two pours or a premanufactured expansion joint of which there are many types. Most are plastic or asphalt impregnated wood fibers, etc.
A control joint is a saw cut or trowled joint that creates a place for the concrete to crack while it cures. This is natural as all concrete contracts as it cures and the water goes away.
Putting in the control joints just ensures the cracks end up where you want them instead of willy nilly all over.
The control joints usually are made to a depth of an inch or 1/3 the depth of the concrete if using a saw. A trowel is the easiest and cheapest way to construct a joint though.
If you use a saw you must typically wait 12 to 24 hours depending on concrete type and weather. Cut too early and the joint looks really bad as the saw breaks out loose rocks. Cut too late and the concrete is already cracked in places you don't want it too plus its harder to cut.

Here is a good website with a lot more info.
http://www.johnbridge.com/control_joints.htm


Sean J Murphy
www.amenityarchitects.com
coming soon www.netcamper.com