I read your column faithfully and always find it very informative. Could you please comment on mud jacking. I spoke to a contractor who felt this process wasn’t durable and I’d be better off getting the concrete slab of my garage re-poured. What do you think?
Mud-jacking is a process where heavy concrete slabs are lifted and moved using a complex hydraulic system. Small holes are drilled in the surface of the slab through which a slurry is pumped into the area below the slab. This slurry normally contains Bentonite clay as well as other components that swell when they are wet. This material can be pumped in to fill any voids that have developed under the concrete slab, preventing further settlement. The semi-liquid, which is under pressure, can also be used to lift sagging sections of concrete that may require levelling to their original position. After lifting, the small holes are patched with concrete and are often the only visible evidence of any repairs.
I don’t agree with your contractor that the process is not durable, as I have seen sidewalks and garage pads that have remained fairly stable for many years after mud-jacking. I too was sceptical about the lasting effects when this process was starting to be used in our area, over a decade ago, but have seen the favourable results. The process does, however, have a couple of drawbacks and these should be strongly considered before contracting the service.
The first and most important consideration is the condition of the original concrete slab to be repaired. If the surface and overall integrity of the concrete is still in good condition, then mud-jacking is an option. This favourable condition can include cracks where individual sections of the slab have settled. Even large cracks can be closed considerably when lifting the heavy concrete pads. If the surface of the concrete is damaged or spalling or the concrete is crumbling, then mud-jacking may not be possible or simply a waste of money. In this case, I would agree that removal and replacement is the only practical option.
The second drawback of this process is the cost. It is not inexpensive to hire a mud-jacking company, as much equipment and expertise is required to properly move the heavy concrete. The fees may often be up to 50% of the cost of newly poured concrete. Again, the condition of the original concrete must be looked at. If the concrete can be expected to last ten to fifteen years after the repairs, then the option may be viable. If the concrete is in moderate condition and in a high traffic area and subject to much deterioration from weather and moisture, it may not last as long as the warranty on the service. It is not practical, in my opinion, to spend significant amounts of money on lifting concrete that is only in fair condition, when it may crumble and fall apart in a few years. In this case, waiting until it is deteriorated beyond practical use before replacement may be a better use of home renovation funds.
Although used primarily for lifting cracked and sunken concrete slabs, mud-jacking can also be used to lift entire buildings that have settled. This is highly risky and sensitive work, and is rarely done in residential buildings. The one area that it may be used is for lifting detached garages that have settled. If your garage is sitting on the slab and the garage is settling in one area more than others, it may be possible to level the entire structure with mud-jacking. This will not only even out the concrete floor, but will improve the entire building. In this situation, if your garage is built on top of the slab, mud-jacking may be a much more economical method for repair as opposed to replacement. To pour new concrete in this style of construction it may be necessary to mechanically jack up and temporarily support the garage, break up and removing the old slab and pour a new floor before replacing the walls on the concrete. This will add to the cost significantly and will be much more labour intensive.
Whatever choice you make, lifting or replacement of the concrete garage slab, obtaining several opinions and quotes is always a good idea. Costs of various repairs, especially when dealing with concrete, can vary enormously depending on the weather, time of year, and how busy the contractors are at the time of construction. Exploring several options should lead to the best “bang for the buck” in dealing with your damaged garage floor.