Estimated reading time: 5 minutes, 46 seconds
According to my concrete contractor John. “There are only two types of concrete, that which is cracked already, and that which has the potential to crack.”
Although your slabs may be “cracking up”…it is no laughing matter. Using cement wisely and properly is an art which is learned by experience. Experience is that illusive thing that is earned by making mistakes and learning from them over many years. At Levco, we understand that just because we can, it doesn’t mean we should. So we regularly use our trusted specialty subcontractors to provide our foundations and flat work.
Like most men, I am acutely aware of my surroundings when it comes to checking out attractive lines. A lesser known fact is that I am also frequently checking out the concrete I am walking on and working around.
As a trusted adviser and remodeler, I am called in to evaluate and repair all sorts of foundation and concrete issues in general. Spring and summer here in Boise Idaho is concrete repair season. This annual ritual gets me involved in a bunch of concrete problem evaluations, everything from sidewalk crack repair and grinding, to slab lifting and foundation crack repairs. The common theme among those in the know is that cracks are inevitable – taking control of them is the trick.
Things that discourage cracking:
- Great prep: this means a well compacted porous chipped gravel and sand mix. at least 4-6inches.
- Keeping the slab and surrounding area dry, moisture encourages concrete to act like a sponge, freeze and thaw cycles are hell on slabs.
- Thickening the slab, a 4″ slab is more likely to crack than a 6″ slab.
- Avoiding harsh snow melting solutions that cause spalling.
- Concrete is rated in PSI, the higher the PSI the stronger the mix, the less likely to crack.
- Installing metal mesh only keeps the cracked slabs from migrating (according to John).
- Installing stress relief joints will encourage concrete to crack where you want it to.
- Planting large trees with shallow roots away from concrete.
The conventional wisdom is that great prep will reduce the risk of cracks but even that can’t stop every crack. My recent experience has been less upon cosmetic problems and more about some serious movement caused by tree roots, and settling.
Repairs techniques we employ run the gamut from simple to complex, here are 5 techniques that we take into consideration and use in order of severity to address the issues at hand.
Crack filling repair:
Sealing cracks is an art. Being patient and methodical is just one part, using the right techniques and materials is a necessity. Our best results have come with good crack prep, foam backer rod, and a top of the line sealer. (The type we use is approved for airport runways). Crack filling is a good tempering measure to prevent moisture from infiltrating the joint and causing frost heaving and erosion of the compacted base. This system works best when there is no slab height difference.
When slabs crack in an expansion joint or any other place, and there is often lifting or sinking. Mismatched slab heights causes a trip hazard. Using a large diamond cup grinder to ease an edge or two can prolong the life of a slab. We will often fill a crack after the grinding takes place.
Uneven slabs are dangerous, a mitigating technique is to drill holes in the slab and pump in a slurry of mix which raises the slab back into position. Although we see some amazing results, this is not a foolproof system. The dream is that you can lift a slab back into position and avoid replacement. This is a good plan “A”, plan “B” (slab replacement) may be required.
This technique is not used for foundations. Crack filling is also used after mud jacking.
Spray foam injection:
Leveling with spray foam is my new favorite thing to do. We have successfully done void filling and lifting of slabs with this two part high density polyurethane spray foam. The process is quick, clean and economical.
These little gems are our “big guns” in the repair world. They have the ability to stabilize a settling problem and lift a foundation back into position. They are large steel threaded rods that are twisted in until they reach a certain torque.
Once set, they are essentially locked into stable soil and can be used to lift off of if necessary. They are also used as a preventative tool to support structures that are built over unstable fill. Helical piers can be inserted at all sorts of angles and can even be used to hold retaining walls.
At some point there is no other alternative than breaking the concrete out and starting over. We always use rebar with epoxy for doweling the old to the new when replacing concrete. In some cases it means lifting the structure back into position, removing the sunken foundation or cracked slab, reinstalling the base, and then replacing the concrete properly.
In this case we had massive gaps and a broken slab. (I joked with my crew that I thought I saw fire and molten magma down one of the fissures). It was like tectonic continental shifting was occurring under the roof. We cut out the bad parts and were able to dowel into stable concrete and re-pour a flat slab with lots of rebar to stitch the slabs back together. Time will tell if we outsmarted the slab cracking.
Remodeling gets us into all sorts of situations, we get to see and fix the results of those that built new a half a century ago and longer. What I’m sure was intended to last a lifetime often does not. Best practices back then are unheard of now as we adapt and overcome.
The good news is that we love what we do and get to use our experience and technology to fix stuff and often make it better than new. That is where we get our satisfaction and where the sweet spot is for Levco.
Your comments are welcome. To ask questions or get more information about remodeling, click here to email me directly, or call 208-947-7261
If you or someone you know is considering remodeling or just wants to speak to a trustworthy remodeling contractor please contact me, you’ll be glad you did.