Thinking about installing a new walkway, patio or driveway and not sure which material to use? Many people face this dilemma and finding accurate information to help them make an informed decision is difficult to find. I’ll help shed some light on misconceptions of interlocking stone and issues that people experience with improperly installed interlocking stone and the importance of planning, drainage and installation.
Firstly, we must recognize the climate we live in and its impact on structural installations of walkways in frost-prone regions. What exactly is frost you may ask. More specifically we are concerned about ground frost, which is when the upper layer of soil falls below the freezing point of water. This causes the water molecules to expand, thus expanding the volume of material in which frost is present. This reaction can cause significant damage to poorly designed structures such as buildings to bridges and in our case, even a new walkway. This seasonal happening can be a nightmare to poorly installed concrete and interlocking stone walkways when proper planning and preparation is ignored.
The 3 main variables that require attention when planning a project are drainage, local soil conditions and base preparation.
1 – Drainage. This is important to decrease heavy frost in winter, eliminate water pooling on the surface and ice build up during winter.
2 – Local soil conditions. These play a role into the structural stability of the walkway itself as the gravel base for this lays on the existing natural soil beneath it. Soil that holds a lot of water can negatively impact the structure of the walkway over time. Therefore, all soil rich in organic matter (which tends to hold moisture very well) must be removed during the excavation stage.
3- Base preparation. After reading about the impact of local soil conditions, you can likely see how important a proper base preparation is. In addition to removing all soil rich in organic matter, we must also ensure to prepare a proper gravel base on which the walkway will rest. This means, the gravel needs to be of a specific grade, depth and well compacted with a mechanical plate compactor. A 1-inch layer of ‘crush dust’ also known as 1/4” minus is installed on top of gravel base with a lazer level to ensure proper pitch for drainage. This layer will later carry the selected stone.
Interlocking stone or concrete?
The large advantage of interlocking stone over concrete is its strength to disperse pressure than lead to cracks. With concrete, if an issue is to arise, a crack appears and little can be done to repair it. Once it becomes big enough and creates a hazard, the concrete would have to come out and new concrete installed which can be very expensive. On the other hand, if an issue is to arise with interlocking stone, simply remove the stones in the affected area, re-level the base and re-install the stones.
There are numerous installations of interlocking stone around that have been installed decades back with little to no complications. The same can be said about concrete as well, but how many walkways have you seen done in concrete that an issue arises and it has been re-laid? Likely zero. In a sense, interlocking stone is not only strong as it’s able to distribute weight placed on it better but allowing the stones to move slightly and flex, but is also more environmentally friendly given the nature of possibly re-cycling it in applications where it has been removed.
A large misconception about interlocking stone is that it will ‘heave’ in the winter, be filled with weeds and be over run with ants between the joints of the stone. This is true if installed wrong, however the knowledge and products exist to eliminate these issues and others.
The heave in the winter, as discussed above, is caused by frost penetrating the interlocking stone and forcing it to leave. If installed properly with proper drainage, frost heave should not exist if all appropriate measures are taken to alleviate water from the walkway, patio or driveway. The weeds that appear in many stone walkways arise from edge restraint not being installed along the perimeter of the stone. This edge restraint is used to keep the stones tight together. Its installed on the gravel base with 10” spikes along the perimeter. Without this product, the stones will slowly separate and the stone joints become larger. These joints then are prone to soil/dirt migrating into the joints and shortly there after weeds appear.
Polymeric sand is used in the joints during the installation of the stone. After all stone is installed, polymeric sand is swept into the joints, stones are compacted to help settle the sand and the process is repeated. After excess is swept up and blown off, sand is misted with water several times and let harden for 24-48 hours. When hardened, it eliminates dirt/soil/sand from getting into the joints which ants love to play in.
This is only an intro into various aspects of the installation of interlocking stone. I plan on writing various posts on issues that we have seen with poorly planned and installed walkways and will write about them at a latter time to help give insight into the importance or the preparation and the issues that can arise if done wrong.
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