Sunday, June 03, 2007
A Concrete example
A while back, I had the pleasure to work in the business of concrete thanks to a good buddy of mine that needed a summer labourer for his construction company. The work is not fun and can be very hard on your body over many years. I developed a huge respect for the men I worked with that do this job for a living.
The picture above gives a great example of a concrete pad that was just poured and set in place. The forms have been pulled off and the saw cuts have been made to help control any cracks that will form. Cracks you ask? Yes! When you live in a climate that experiences cold winters that go below freezing, chances are your concrete will shift slightly and crack....
The saw cuts are important to a concrete pad. In our North Eastern climate, we experience frost! Sometimes the soils are poorly drained as well and that makes frost an even more important issue to deal with.
We see in these photos a gravel base under the concrete which allows for water to flow away from the pad but it is not always perfect! Water can pool under the pad once the soil is graded back to the top finish layer of the concrete pad.
That is why the saw cuts are made in the smooth surface. I like to call it stress cutting... these photos show an example of flat-walk sidewalks. The cuts are done about every 5 feet (shown as white dust in the picture below created by the saw as it cuts the material) The idea is to control where the cracks will occur and actually lay out a cut pattern with geometry so that it looks like a design was followed.
Another thing you will notice in these photos is that the pad has been poured with a consistent thickness. You want a uniform thickness in the concrete to ensure no weak points should the pad be subject to frost or vehicle weight.
Generally for a patio in a residential application, 4 inches of concrete is acceptable...if it is a driveway, you may need a thicker pad and deeper gravel base to handle vehicle loads.
If you intend to have concrete installed around your home, make sure you ask the crucial questions to your contractor...ask about proper drainage, frost & saw cuts, surface finishes and thickness. See that the sub-base is properly compacted and that the concrete is of good quality.
How to tell about quality?... It should have a thick consistency like a cake batter... workable enough to shape it, but not runny and loose to where it flows like water. Also, if having coloured patterned concrete installed...make sure the concrete colour dye is mixed into the entire load of concrete.
Nothing is worse then a surface application of colour and experiencing a crack that exposes the plain colour under the surface. If you use salt to control ice build up in winter, make sure you seal your concrete to help protect it's finish!