You have finally decided to tackle the garage cleaning project your spouse has been talking about for months. You do not even mind so much because you know that you will have a place to park the car when you’re done. You are moving along with few problems when suddenly, you see it: a crack in the slab.
You have no idea how long the crack has been there. You are also concerned you might find other cracks as your cleaning job progresses. What do you do? How do you fix them? Is your whole house going to slowly sink into the earth until it is gone forever?
There is a temptation to jump on these sorts of things and assume that the entire slab has to be ripped up and replaced. But complete replacement is not the only way to fix a slab. It is also not always necessary. The most appropriate repair method is dictated by what is actually causing the cracks.
Surface Cracks Only
The experts at the Concrete Raising Company in Salt Lake City, Utah say that garage slabs are often subject to cracks that are considered surface-only. They say such cracks are limited only to the screed. What is screed? It is a cosmetic layer of sand and cement with no aggregate added.
Concrete is very difficult to finish so that it is completely smooth. So when you want a cosmetically beautiful finish, like a garage slab for example, you add a layer of screed over the top of the concrete. Its lack of aggregate makes screed a lot easier to finish.
More often than not, cracks observed in garage slabs are limited just to the screed. This is especially true in garages that are actually used for their intended purposes. The screed just doesn’t hold up to the constant weight of heavy cars over the long term.
Fortunately, the fix is easy. You just fill the cracks and apply a new layer of screed. Then you can call it a day or paint the floor to hide your repair.
A Sinking Slab
Not every instance of garage slab cracking is limited to the screed layer only. Sometimes, cracks run far deeper because the slab is actually sinking. If such sinking is significant enough, you would see it with the naked eye. But if not, you might have to rely on other means of discovering it.
You can place a level on either side of the crack and check the reading. If the entire slab is sinking, you should notice tilt in one direction or the other. In the absence of a level, simply set a ball on either side of the crack and see what happens. Just note that a lot of garage slabs naturally slope from the back of the space to the front. And if not, your slab might naturally slope inward to encourage water to flow to a center drain hole.
At any rate, a sinking slab cannot be repaired merely by filling in cracks and applying a new layer of screed. The slab has to be raised or replaced. According to The Concrete Raising Company, raising is more cost-effective and easier.
Concrete is raised by pumping either a natural or synthetic material into the soil underneath the slab. The material fills any existing voids and, as pressure builds, gradually restores the slab to its level state. In then hardens to become a solid support that should last for decades.
If you have noticed cracks in your garage slab, do not panic. The fix might be easier and cheaper than you imagine.