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When installed properly using the best base for your paver project depending on the application along with proper compaction of the subgrade and base material, the added layer of a geotextile to separate the subsoil from the base, and geogrid within the base to stabilize the aggregate, a paver project should last for a significant amount of time. However, for years and even still there are unfortunately projects that do not stand the test of time. In this article, we are going to investigate what may be the causes of certain failures, how to prevent them, and how to fix them.
How to Fix Sunken Pavers
Sunken or uneven pavement surface are unfortunately common problems with any pavement surface over time. Fortunately for pavers, you can lift them and reuse them after fixing the base. This is a major benefit compared to other pavement surfaces such as asphalt or concrete where the removal of a section would require a patch job or redoing the entire project. This is where pavers outperform these alternatives, along with several other reasons.
However, it is not the problem of the pavers, asphalt, or concrete that they are sinking. The problem is in the preparation of the base to sustain the pavement surface over time to bear the loads that it experiences.
How to Keep Pavers from Sinking
The number one cause to pavement surfaces sinking or becoming uneven is improper compaction of the base material. Using the right compaction equipment for a project allows you to compact efficiently and effectively on any project to ensure you are achieving optimal compaction of the subsoil and base material. This is especially common in high traffic areas and along the foundation of a structure.
Geotextiles and geogrids should be used to help reinforce the base and separate the subsoil from the base material. A geotextile is primarily used to separate that subsoil from the base material to avoid any contamination between the two caused by the load. While geogrid is used to help stabilize the aggregate in the base material under load from the surface of the pavement. Each of these items will only help support the longevity of a pavement surface when installed properly.
Some pavers become uneven and heave because of other problems. For example, you cannot stop tree roots from lifting pavers. This needs to be considered when first installing pavers near trees and their root systems. It is a risk that you take whenever you do decide to pave near these. The solution is to either remove the tree so that you do not have this problem. Alternatively you can consult with an arborist to see what they recommend. Sometimes you can remove the pavers and have the arborist plane down the tree roots if they feel this is achievable. Though this is a short term solution.
Drainage is an extremely important variable to also consider when installing any type of pavement surface. Water can become a major cause to pavement failures if it is not redirected or relocated to a drainage location. Downspouts coming off of the structures that you are paving next to need to be redirected preferably underground so that this water does not erode any material from the base of these structures. Standing water in drainage pipes that become clogged will also freeze in the winter and heave the pavers up causing tripping hazards.
Base material for your pavers should allow for the drainage of water through it. This is why stone dust should never be used in any installation. This soaks up and traps water causing significant problems in the future of your paving surface. Additionally, washout of the base material is common especially in projects like a raised patio where fines of the base material wash through the gaps caused by movement in the retaining wall. This is where an open graded base can help prevent that washout in addition to a geotextile.
A free draining base material that is properly compacted will allow water to drain through it and into the subsoil. If the subsoil does not allow for water to flow through it freely, then additional drainage should be installed for that project to ensure proper drainage.
How to Repair Sunken Block Paving
It is actually quite simple of a process to lift and re-lay. It is labor intensive and involves removing and cleaning the sides of the pavers where there is likely stuck polymeric sand. This is the time consuming step in the process as you will want to clean the sides of the stones prior to stacking them and reusing them otherwise the laying portion of the project becomes a time consuming process of cleaning and placing the stones. Additionally, cleaning the stones on top of your bedding layer or stones that have already been laid causes issues.
The bedding layer is replaced (we never reused the bedding layer because of organics contaminating the aggregate) and re-levelled with the pavers being re-laid and a jointing compound is then installed into the joints. At times before replacing the bedding layer we would compact the base material once again with our compactor.
There are a few ways in which you can repair uneven pavers. Whenever we meet with a client in regards to this type of work, we provide (or used to provide) three solutions:
- Replace Bedding Layer
- Replace the Base
- Replace the Entire Project
In this scenario, we would remove the pavers and dispose of the bedding layer. At this point, we would find out or already know what the base consisted of. If the bedding layer was concrete sand and we were only removing a section of this project, we would re-install the bedding layer using the same material. However, if this was a full project lift and re-lay we would remove the bedding layer and replace it with a 1/4″ angular crushed clean stone or HPB.
The reason why we replace the bedding layer with most of these lift and re-lay projects is because the joint material was usually washed out or overrun with dirt which contaminates the bedding layer with organics. In this case, we remove it and replace it with clean material rather than reusing it.
Often times with lift and re-lays we found that the base material consisted entirely of stone dust and needed to be replaced completely. This is where we would replace the base material of the entire project and is obviously more costly of a solution. However, this is basically a brand new project in terms of us providing our warranty on the project and ensuring the client a properly installed base. This assumes that the pavers are reusable. If they are not, then the next option is the best.
This is only slightly more expensive than the previous option. In this case, the entire project is coming out and we are installing from scratch. This saves having to manually pick up each paver and clean it. This saves that labor cost while only costing the additional cost of pavers and delivery.
Some tips and tricks that we have learned over our experience completing these projects include:
- Counting the number of pavers that are unusable and seeing whether or not these are replaceable either with pavers being kept by the homeowner or at a supplier. Pavers and color blends are constantly becoming discontinued and finding the right paver to replace broken or chipped pieces can become difficult. The solution to not being able to find the pavers you require is to install a new border (assuming the existing border is the same as the field of this paver project) or creating an inlay with new pavers. This will free up some of the old pavers to be reused where needed.
- Do not count on all of the pavers being lifted to be reusable even if they look like they are in good condition on the surface. Especially if they are installed on stone dust. Sometimes the pavers will be breaking down from the bottom up. Have a back up plan communicated with the homeowner about this possibility and a solution ready to go based on the previous point.
- Do not try to lift and re-lay a small area. When we were first starting out, we would do this and would get into trouble with making it look good. Now, we opt to do a large area or the entire project where possible. If the pavers are sinking in a 2 foot by 2 foot area, try to lift and re-lay at least a 5 foot by 5 foot area or the entire row of pavers that this covers. What you will find is that for pavers to sink, there needs to be some sort of lateral movement. If you only lift the pavers that sunk, you would be left with larger gaps between the interlock when those pavers are re-laid. The larger the area you can lift and re-lay, the better the joints will end up. Now in our business, we only do complete lift and re-lays. Never a small portion of the project.
- Efficiency is important. We often lift the pavers, set them on a pallet to the side, complete what is needed with the base and bedding layer, and re-install the pavers. However, it is more efficient if you are not replacing the base to remove the pavers in a row at the length of your screed pipes, placing them to the side, re-screeding that area, and then re-laying those pavers while moving on to the next section.
- Power wash the pavers at the end prior to installing the polymeric sand. We once did this before removing the pavers, but then stacked the pavers and the old dirty jointing material just made the pavers dirty again. In retrospect, this was a dumb thing to do.
- Manage expectations. A lift and re-lay will make the project look better. But if you are not lifting and re-laying the entire project, do not expect perfection. Also, if you are not completely replacing the base or identifying the problem that caused this (which is most likely compaction or water) then it is just a short-term solution.
- Use this as an opportunity to provide your client with several solutions to the problem such as replacing the bedding layer, replacing the base, or re-doing the entire project at three different pricing levels. You should also take your time to investigate what may be the problem to provide the best solution forward and advice for your client.
- Do not offer a warranty unless you replace the base.
Cost to Repair Sunken Pavers
As mentioned above, we provide three different pricing structures for lift and re-lays. Replacing the bedding material, replacing the base, and completing a brand new installation with new pavers. With this, we are able to provide insight into which is the best option for our client moving forward. The benefit to pavers is that they can be lifted and reused. There is nothing wrong with taking on these projects and they can even present a very profitable business opportunity that can be scaled much easier than a custom design build business. This is because a lift and re-lay business is not custom work and there is already a blueprint in place for each project.
The cost to repair uneven pavers depends entirely on the business that is servicing the project. Typically smaller businesses can take on this work because it is heavier on the labor aspect to the install and less reliant on larger equipment to complete it. If you want to learn how to price your landscaping projects by taking into consideration your overhead expenses, labor costs, and materials while ensuring you are making a profit on every project, check out our course on pricing landscaping jobs.