We’ve all heard the children’s story about Goldilocks and the Three Bears where the porridge is “too hot” and “too cold” then “just right.” We can relate this to many things in life where we are looking for the correct balance. Not too much, not too little, but that perfect level of “just right.”
As strange as it may sound, the analogy can be compared to some of the challenges associated with mudjacking. In this there are certain, “delicate balances” that we are trying to achieve, which might be in the middle of two less than desirable opposites.
Very often with mudjacking, the goal is to lift concrete which has settled (sunk) into the ground below. Very often there are voids between the concrete and the ground, leaving the concrete slab improperly supported. Mudjacking can fill those voids and lift the concrete back to its original position.
An inherent assumption is that the concrete is strong enough to withstand the lift. This can be impacted by the age of the concrete, how much rebar was (or was not used), weather conditions when the concrete was poured, and the quality / skill of the concrete team who initially installed the concrete. (In many instances, we could be trying to lift concrete which was poured decades ago!) High quality concrete has a much better chance of lifting the concrete right back into its original position. Low quality concrete however, can often lift back to its original position as well, but the challenge it can create is that the concrete can be lifted to a certain level, but after that, in some instances, it may begin to crack.
This aspect creates the challenge of a delicate balance with mudjacking (and any kind of concrete leveling approach for that matter): being able to achieve enough lift, but not lifting so far that the concrete cracks.
Compounding this problem, is that the mudjacking team rarely knows the quality of the concrete until they actually start to lift the concrete. In some jobs (most cases), the slab easily lifts right back into place with no cracking, in other (rarer) cases the slab is slow to lift and quick to crack. At that point, the mudjacking team is making a decision of how much to lift. At some levels, there are value judgements which must be made (ie: there is some “art form” to it); this is also where selecting a quality contractor can pay great dividends. Depending on the circumstances, there are instances where there is a limit to how much lift can be achieved without negatively impacting the concrete being lifted.
It can be helpful for the customer to be present when the concrete lifting is going on so that the foreman can have a conversation with you about the results and the questions they are having.
Quality of the concrete is a major factor which impacts this delicate balance, but other factors can also have an impact. The quality of the soil below the slab can have an impact on how much pressure can be applied to lift the concrete. Poor underlying soils can limit the amount of lift achieved with mudjacking.
Similarly, if the home has poor drainage under the slab, water runoff can wash out the supporting soils under the slab and if they are chronically wet, as you might imagine, muddy / wet soils will not support the concrete (and mudjacking materials) as well as solid soils. Drainage issues can be a huge cause of settling concrete, both initially and on a recurring basis. (Note: we can also help you with drainage issues!)
Another factor is the weight of the concrete we are trying to lift. Obviously, it is easier to achieve strong lift on a small section of a sidewalk as compared to a large set of stairs and porch. Simply, the weight of one is much larger than the other.
And while these elements impact this “delicate balance” in the vast majority of situations, we are able to achieve that balance and lift the concrete slab back into place.
This aspect also points out one of the advantages of mudjacking over polyjacking. With polyjacking, the injected foam expands over a period of time providing less control over how much material is injected under the slab (as compared to mudjacking, where the control is higher.) Because of this, mudjacking provides more opportunity to prevent “overlifting” than you can typically achieve with polyjacking.
A final side note, is that with mudjacking, if we do have concrete cracks as a result of the lifting, we will typically stop lifting to minimize those cracks, even if we do not achieve the full level of lift desired. We will also cosmetically repair those cracks at the time of the repair as part of the project. Mudjacking is significantly less expensive than replacing the slab.
The advantages of mudjacking are many, however, the more informed you are about your project, the more we can work together to ensure you get the most ideal outcomes.