When pouring patio slabs, it’s important to have done the proper preparation thoroughly beforehand. While some home improvement tasks lend themselves to being fixed or replaced if things go wrong, fixing or replacing a concrete patio can be a daunting task. So much so that you will likely just have to live with the mistakes for years or even decades. For this reason you need to do your homework and make sure you know the ins and outs of the project before setting anything in stone (or rather concrete).
Patio slabs are heavy, and need to be supported properly. Often the soil when compacted enough will be suitable and no foundation will be necessary to pour, but don’t take it for granted. If the soil is often damp, or the soil is too loose, the patio could sink over time. In such cases you may need to dig down deeper to harder soil layers, and build the foundation or support posts from there.
Other concerns with the foundation are what is down there. Roots from larger trees (or smaller trees which will become larger over time) can break up even concrete over time, and can also cause the patio slab to lift and tilt. Other problems can arise from buried utility lines for your house, as the patio may restrict access to those lines. Keep in mind your future projects too… a misplaced patio may make running drainage or irrigation lines much more difficult tasks than they need to be.
You also need to bear in mind the intended usage that the patio slabs will be expected to undergo during it’s lifetime. If only light foot traffic and a couple of chairs with their occupants will be the most load it has to hold up to, you can go with a slab that is less thick than if you will be parking vehicles there at times.
This holds true not just for the thickness, but for the need for steel reinforcement as well. Heavy loads may dictate larger diameter of steel be used. Even in light load situations you should probably plan for including some steel reinforcement for your patio slabs.
Creative Commons Picture Courtesy of GardenFocus
Concrete will tend to crack over time, and the steel will help keep the patio together and providing a level and even surface. Without it, a crack can lead to a portion of the slab slipping, leaving an edge that can catch the toes of those walking by. Not only is this aesthetically detrimental, but is also a safety issue. These concerns have to take into account the nature of the foundation as well. With softer soil subsurfaces, the need for steel reinforcement becomes more pronounced than with more solid foundations. Also of note is the climatic conditions in your area.
Drastic changes in the temperature of the concrete can cause cracking, and so increases the concerns in that regard. Even if temperatures in your area are relatively stable the temperature of the concrete may not be. Sunlight can warm the cement faster than it warms the air, and so leads to discrepancies.
So be sure when pouring your new patio slab to bear these issues in mind. It just may save you from a lot of headaches and costly repairs for years to come!