Are you interested in how to build a concrete patio or walkway? Here is my experience.
The plan
As you can imagine, the idea was to be able to hang out in the backyard and walk around the house on a solid, level and maintenance-free surface in any weather with lots of traction.
The design
I decided to go with concrete, as opposed to interlock stones. The concrete I chose was basically the same one that the city uses to make sidewalks. It is durable, rough and has cool synthetic fibers mixed in it to make the it bond stronger.
The prepare the base under the concrete would be about 6 inches of 3/4 crush gravel (this is basically 3 parts large stones mixed with 1 part smaller stones). The two different sizes help to compact the mixture. I also estimated that for my (and my neighbour’s job) I would need 19 tonnes of concrete. That sounds like a lot … and it was. I had two cement mixer trucks show up.
To prevent rain water from flowing into your house you need to make sure that the forms slope down and away from the house at rate of about 1/4 inch for every 4 feet. To reinforce the concrete I decided to use a steel wire mesh. This was probably not necessary, but I thought it would be very cool.
I would also have to prevent the concrete from cracking but more on that later.
Getting started and getting help
Pouring concrete is a huge job and so is the prep work. For starters, after marking off the layout, I decided to to rip out any grass to make sure that there will be no chance of grass coming up through any concrete cracks in the future. Before starting I was also able to get help from my neighbour to help me make sturdy wood forms. This really paid off because what I had in mind would not have been strong enough. Here is an example of finished forms:
After the forms were build it was time to fill in the gravel, level it (by raking it) and compact it. We rented a pneumatic “wacker” to get the job done. It was well worth it for the area.
With so much concrete coming I needed to get some family and friends to help me wheel the wet cement from the truck to the back of the house. The key here is to work quickly and withouting spilling any cement mix.
As you can see below, a well fed crew is a happy crew.
Once the concrete is poured into the forms, you need to smooth it and decide on a finish. You definitely want to hire an experienced concrete finisher for this. He is the one with the green rubber boots. When he showed up I thought he was going fly fishing but it turns out he was just experienced and prepared.
Below is his finished work on the steps.
I also decided not to add any “designer” colour or pigment and no finishing glaze. From what I have seen in the houses on my street, the colour seems to fade, the glaze finish peels, chips and pops up in pieces. Not to mention, it is dangerously slippery when wet. I still don’t understand why anyone would want the wet look for a walkway or patio. For mine, I asked the finisher to sweep the cement surface with a broom to give it some roughness.
Curing concrete
Once the concrete is surface-finished you need to let it dry slowly. On a hot June weekend, it meant I was guarding my fresh concrete for two days with a water hose and misting it every couple of hours.
Once the concrete turns solid white, you can stop the watering and step on the patio. I must admit that thoughts of quick sand crossed my mind when I first stepped onto it.
Preventing concrete from cracking or how to make expansion joint cuts
Concrete will shrink in the winter and expand in the summer. These movements will cause the concrete to shift or crack at the weakest areas. You may not be able to totally prevent this but with some planning you can control where the cracks will occur. The basic idea is to use a concrete saw to cut lines (or controlled expansion joints) in the concrete and space them correctly. The cutting is done after the concrete cures completely. I have done mine about 2 weeks later.
To start , cut lines that extend the contours of the exterior of the house. For example, since my patio and walkways on both sided of the house are connected, I made one cut along the back wall of the house and another cut along each of the side walls. Try to cut as much of the concrete as you can (without cutting the wall of the house or a fence). You will find that over time the short uncut portion of concrete will crack by itself as if to complete the line. This is perfectly normal and is actually what you want. That is, you want any cracks to follow your line and not make a weird zig zag somewhere in the middle.
Next, you need to figure out how far apart to make the rest of the cuts. Obviously, you want to minimize the number of cuts unless you are looking for a chess board pattern. The thicker the concrete, the less it is likely to crack so you need to make fewer cuts. I used the rule that for every inch of concrete thickness you should space the cut lines at least every two feet. In my case the average concrete thickness was 4 inches so cuts would have to be at least 8 feet apart. In reality, you may have to adjust the spacing to suit your location. For example, you don’t want one of the cut lines to be slightly off the centre of the patio stairs. It will look funny. So instead, place the lines on either side of the stairs. Well, you get the idea.
Since this project was my first attempt at this, I wasn’t sure on how deep the cuts should be. The answer is that it doesn’t matter and the saw blade will decide that for you. You will never see how deep the cut is once the concrete cracks below it.
Conclusion
The job was done in the summer of 2004 and the patio and walkway are in perfect condition, i.e. no cracks, shifting, chipping or breaking. My only mistake in retrospect was pouring concrete fence to fence with no clearance. This could become problematic if I ever want to replace my fence posts or decide to plant something large along the fence for privacy. That may be another blog in the future.
Tags: concrete, cracking, dyi, how-to, machine, maintenance-free, make, mighty, mixer, patio, plannig, pouring, Preventing, rebars, residential, truck, walkway
Nice Patio!!!!
Thanks for blogging this. I have a ton questions for contractors and this answered some of them.
Nice job!! Thanks for all of the information. We just finished our patio and your blog was so helpful in knowing all of the steps that generally aren’t in an instruction manual.
Thanks for writing this.
Looks like a nice job, however, I would like to point out that saw cutting of concrete 2 weeks after placement is way too late. Saw cutting to prevent contraction cracks should be done as soon as concrete reaches enough strength to carry the weight of a walk behind saw (typically before concrete starts to cool down)
Excellent site, keep up the good work
Hi! I was surfing and found your blog post… nice! I love your blog.
Cheers! Sandra. R.