Concrete slabs are one of the most commonly used materials in construction. They are cheap, easy to lay, and extremely strong. They are more than able to support the weight of a house, hence their usage in the foundations of a number of homes. Where they are vulnerable, however, is to sinking or subsiding. When a concrete slab is laid on an unstable surface, there is a danger that part of the surface will not support the weight of the slab evenly.
This means that part of the slab will start to sink, eventually causing it to crack. This can undermine the structural integrity of the house. Mudjacking is a tactic for addressing sinking by raising up the surface underneath the concrete slab, allowing it to lift and then level the concrete. As a technique, it has been around for over 70 years.
This guide will go through the core principles of mudjacking, before discussing whether you may (or may not) want your slab to be mudjacked, and finish with a discussion of what you can do to prevent mudjacking from being necessary.
WHAT IS MUDJACKING?
Mudjacking – also sometimes known as slabjacking, concrete lifting, and slab leveling – is a relatively straightforward way of dealing with a fairly major problem. If your concrete slab has sunk as a result of poor soil conditions underneath, mudjacking is an ingenious solution.
The technique involves drilling holes through the concrete slab to the soil below. Then a mixture of soil, sand, and cement (known as ‘mud’) is pumped through the holes. This fills the space vacated by the soil, raising up the concrete slab and providing it with a solid base on which to rest. In some cases, you can literally see the concrete slab rise up as you pump in the mud.
As perhaps may be expected, mudjacking is a job only for a trained professional if, for no other reason, than there is a great deal of specialist equipment needed. A professional will be able to assess exactly where to drill the holes, the ideal mixture to create the mud, and the precise amount to pump through the holes. They will also then be able to assess the stage at which the concrete slab is not just level, but capable of remaining at the level for the long term.
One of the additional benefits
of working with a professional is that they will be able to fill in the holes that they have drilled. A really skilled mudjacker will be able to make the holes (almost) invisible, thus minimizing any aesthetic concerns you may have had. The entire process is relatively simple for a professional, and doesn’t require more than a couple of days of work (obviously depending on the size of the slab and the extent of the sinking).
AVERAGE COST OF MUDJACKING
Mudjacking is not a process you’d undertake if you did not have a sunken slab – it’s not even widely used as a preventative solution. However, if you do notice subsiding in your concrete slab, then there are several reasons why mudjacking is the optimal solution.
Some of these reasons include:
WHEN MUDJACKING MIGHT NOT BE THE RIGHT FIT FOR YOUR PROBLEM
Although mudjacking has many advantages, as a technique it’s not without its limitations. Some of these may make it unsuitable for all projects.
THEY INCLUDE THE FOLLOWING:
The ‘mud’ used in mudjacking is not always ideally suited to all climates. In the northern region of the United States, where winter can be extremely cold, the constant freezing and thawing of the ground can cause problems, as the ‘mud’ can change in volume. If the material breaks down, and there is not adequate drainage around the area, there is a chance that the concrete slab may begin to sink again.
If you have major issues with the soil underneath the slab, mudjacking may not be an ideal solution because of the weight involved. The ‘mud’ is extremely solid (and therefore extremely heavy). If the soil is particularly soft, there is a danger that the mud will eventually start to sink and the problem will return. In this case, however, the problem is far greater than can be addressed with mudjacking.
The holes needed to drill into the concrete can be problematic. Firstly, there is the aesthetic concern, since the filled-in holes don’t necessarily match the concrete around them, and are therefore visible. Secondly, there is the fact that drilling holes in the concrete may compromise its structural integrity and lead to cracking. This can, therefore, be a worse option than relaying the concrete slab.
WHAT CAUSES FOUNDATIONS
Of course, the best long-term solution is not reactive, but proactive. Even if you’ve had your slab mudjacked, you should be aware of the causes so that you can do everything possible to prevent recurrence and to ideally avoid it in the first place. Below are the most common causes of foundation settling:
As mentioned throughout the course of this guide, poor soil conditions are the primary cause of slab sinking. If the soil is loose, prone to flooding, or simply cannot take the weight, there is a strong chance that a concrete slab will sink. If the soil becomes waterlogged, it also impacts its ability to hold weight, so soil on a flood plain may also experience sinking.
Although some soils don’t lend themselves well to taking a concrete slab, other soils do but are not always adequately prepared. Before laying a concrete slab, the soil must be leveled and tamped. If one or both of these tasks is missed, then the slab stands a strong chance of sinking.
If roots from large trees grow under a concrete slab, they can upset the soil content, thereby leading to sinking. This is most commonly a problem in older homes, where tree roots may have grown totally out of control. As a home or business owner, the best course of action is to maintain the roots of all nearby trees before it becomes a problem.
Leaks in sewer lines can be problematic as it introduces additional water to the soil. In older (particularly copper) sewer lines, this is a common problem. To compound this problem, a sewer line leak may introduce both water and nutrients into the soil that can attract roots to grow.
One of the most interesting technological developments in mudjacking has been the development of polyurethane alternatives. Although these are not yet as widely used as the traditional ‘mud’ approach, the expiration of the patent means that more and more companies are investigating their own alternatives.
This means that there is likely to be a surge in the usage of polyurethane materials and processes in the coming years. Although this challenges the environmentally friendly elements of mudjacking, it also provides a strong, stable base for a concrete slab without the weight that can cause the ‘mud’ itself to sink.