Many people want to install pavers over concrete. Perhaps they have an old installation built on a concrete slab, or perhaps they want to avoid doing the work necessary to rip up an old concrete patio or driveway. Installing a base of aggregate may be the best option, but perhaps the best is not needed in this situation. A consumer or contractor may ask: can laying pavers over concrete be a good idea?
Yes, But…The Disadvantages
In short, yes, it is possible, but with a few things to keep in mind. First, having a pre-set base like concrete will restrict your creativity and freedom to add to the patio, driveway, or walkway. With an aggregate base, you have the ability to create new patterns or shapes; this is not the case if you are installing pavers over concrete. Ultimately, whether or not laying pavers on top of the pre-existing slab will depend on the project type itself. Laying pavers over a concrete patio may work fine, since it will experience little stress, but a driveway constructed in this way may not be able to stand the stresses of vehicles.
Grades and Heights
Second, the height of the installation will obviously be higher than it was. For instance, if you put pavers over a concrete patio, the height of the patio will be increased by the height of the brick. This may not be a big deal with certain applications, but in others it may be problematic. For instance, installing pavers over concrete for a pool deck may be a risky proposition, because if the pool pavers are too high, they may create a tripping hazard near the pool or may make people cut themselves when they are entering or exiting the area. Thus, you’ll probably want to install a new base for a pool area, unless you are using thin pavers and the heights work fine (see below about thin pavers).
Another potential problem when it comes to the heights of the new brick may relate to grades or slopes – if you have issues with water pooling in particular areas, it probably won’t be corrected with this new paver installation. Make sure that there will be no problems with water as a result of this installation, as it will not be able to drain easily through the pavers with the concrete underneath – the last thing you want is a flooded yard or basement. You will also need to consider how you will surround the installation – with soil, mulch, or stone. Otherwise the concrete slab and borders will be exposed and will not look good. This amount of material could cause problems itself.
The Finished Product Depends on What’s Underneath
Third, installing paving stones over a concrete slab may be easier, and thus within the skill of a homeowner, the finished product may be somewhat disappointing. In particular, if freezing and thawing during the winter months cracks the concrete underneath, the patio, driveway, or walkway may be thus adversely affected, perhaps settling or developing its own unsightly cracks or sunken patches. Note that water and ice are constant dangers – if the water seeps through the patio and rests on the concrete layer below, and this water freezes, you may experience nasty heaving and settling.
Finally, the project itself may just not look as good as one installed over a proper base. For instance, efflorescence is a problem for all concrete paver installations. This is the phenomenon of a white, chalky residue appearing at the surface of the pavers. While this is entirely normal and will go away with time, the problem is exacerbated if the paver rests on a solid concrete bed.
If You Do Decide to Lay Pavers on Concrete…
Make sure that your concrete patio or driveway is entirely clean before you putting the pavers down. This will help prevent some future problems with your project. Actually installing the pavers will require some different methods and materials than a normal installation as depicted on other parts of the site. For example, you’ll probably have to use mortar for certain applications, as the standard sand bed/compacting method may not work. Make sure your contractor is trained in doing this procedure and has experience with it. If you are installing the project yourself, make sure you check with someone in the know (like an experienced contractor) who can help you with your particular situation and its installation.
Material Types Matter
In addition, using different materials on top will affect the conclusions described above. Using concrete pavers is one thing, but using stone or brick pavers over concrete is another. You will have less problem with efflorescence with these options, but you may have more drainage issues with them, and they may not withstand certain stresses well. Another thing to consider here is price and cost – if you are going to lay a lot of money out for expensive materials like natural stone pavers and flagstone, why not just go the extra mile and get it installed correctly on a fresh base?
One viable option if you’re just looking for a veneer on your project is to install thin pavers over concrete. These will replicate the look of regular pavers while also helping to preserve height – they are thin so that they don’t create a tripping hazard or mess up grades. However, note that they will have to be set with mortar, so you might have cracking and other disturbances appear, especially if the base below is faulty.
You could also lay down outdoor patio tile on top of an already existing concrete installation – this will give the project the new look that you desire with a fraction of the cost and time.
In short, installing pavers over concrete is doable, but has some negatives you need to be aware of. If money or time is not an issue, starting your project from scratch is the better choice. But if you are prepared to compromise on looks and customizability, installing paving stones over this base should work fine.