If your old concrete patio, slab, sidewalk, or porch needs a little uplift or you’re just ready to update its look, upgrade your patio by installing pavers over concrete. This simple yet clever solution to old concrete patios can be easily done with very few tools and even less experience. Any DIY enthusiastic or regular home improvement guy and do this project over the weekend.
Why do it with pavers? Concrete already provides a strong base to install pavers. It just needs to be free of cracks and other imperfections. You can even fix it for this project as it isn’t too hard to fix concrete.
The good thing about installing pavers on top of the concrete is that you save nature a bit by not taking the concrete to the landfills, those things are full of concrete already. As said before, this is also an easy DIY project. It can be done with sand or mortar/thinset and I’ll explain it down below.
Laying pavers on concrete base
There are few ways to lay pavers on concrete base. You can do it by using sand, like in the ground, or use something that will adhere the pavers to the concrete like mortar/thinset. If you want to overlay pavers over concrete, here is how to do it both ways.
Set up a good base for pavers
Before we build anything, the base has to be whole and free of imperfections. There is an article here on how to manage that. After that, we need to be sure the concrete slab is sloped in the right direction. If it’s not, we can still fix it with mortar/thinset.
We can also fix all the places where there is a place for water puddles when it rains. We don’t want the water to stand there even under pavers. Easy way to see this is using a garden hose to water the concrete slab and then mark the places with a colored pen so we know the places.
I’d not try to fix slopes with sand as concrete won’t let water through. If it’s an uphill battle for water to exit, it will still go towards a house or other wrong direction despite the sand. So we fix this first if needed.
So we come to the point that water needs drainage. If we install the pavers with sand, the slope away from the house has to be maintained still so the water will go out of our patio.
Sand over concrete installation
For sand installation, an edge needs to be built around the patio. When you have it, you can fill the bottom of the patio with installing sand for the pavers. It works almost the same as it does when you install pavers in the ground. You need to compact the sand a little and use a level to screed it level.
Then you place the pavers into neat rows like in this guide here. Cut all the pieces that need to be cut and install from one end to the other, row after row. Remember to leave little space between pavers, if they don’t have auto joints. You need to put a little sand in the joints after you’re finished with the surface so the whole patio will be compact.
Then it’s just regular install with sand and how you want to build. Cut stones to fit and fill joints with sand. Remember to leave gaps for the sand, there usually are auto joints. Compact the pavers in the end
Install pavers over concrete with mortar
Begin by thoroughly cleaning away any debris or loose and crumbling concrete. A pressure cleaning or acid washing may be necessary for heavily molded or smooth finished concrete. A quarter gallon of muriatic acid mixed with a few gallons of water will easily take up any problems that the concrete may have bonding with mortar.
The problem with the smooth surface is, that it doesn’t provide a good surface for thinset to adhere to. The surface of the slab after pour and finishing with a float has a “glue” like substance that has to be ground off if someone wants to put mortar in it. The acid will do the same thing here.
Now it’s time to wet the slab down entirely before applying mortar and keep it wet as you apply more thinset. You don’t want there to be water puddles or water on the surface of the slab. It just needs to be moist enough for the concrete to change color.
This will stop the slab from sucking all the moisture from thinset and hardening too fast. This way the thinset will cure for a longer time and it will be harder. Also, it will help the thinset to adhere to concrete a little bit better. Same principle as with concrete.
On porches, patios or other concrete slabs that break against a structure or a sidewalk with the longest and straightest edge is where you need to begin setting pavers. Stack several rows of pavers against the wall and look at the pattern. If it is what you want, continue to the next step, otherwise, make the needed adjustments before spreading any mortar.
A layer of thinset spread about one foot in width with a ¼” notched trowel will begin the first row once you’ve laid it out. Setting larger pavers will help cut down on production time. Many sets of pavers come disguised as multiple pavers. These can be set in unique patterns and designs that make manipulating pavers easier by requiring less cutting.
Offset multiple pavers can simply be turned to create unique patterns. Cutting the starter paver in half on every other row also offsets patterns for a unique design with minimal cuts.
Stack additional rows of pavers at least two rows ahead of the actual installation to ensure a proper fit and pattern before gluing it down to the old concrete patio. Spreading a layer of mortar no thicker than two feet at a time prevents the mortar from drying too quickly. Don’t forget to keep the existing concrete slab wet as you apply the thinset.
Once the pavers have all been set in place, allow the set to dry for 24 hours before walking on it. Once dry, you can begin sweeping paver sand in between the cracks. A push broom and bagged sand are all that is needed. Fill in all of the cracks overflowing, moisten slightly, and then sweep in more sand. In the following days as the sand settles, sweep in more sand as needed.
Installing pavers over concrete can give your slab a new life. It’s important to think about the pros and cons of doing with sand or thinset.
Personally, I think both ways can work if the water control is handled properly. Standing water on concrete is most of the time bad idea, especially where we can’t see it.