concreterepairroof
I have a slab of concrete over the front entrance of my house with some serious cracks in it. I don't actually know what the proper name for it is, which makes this difficult to Google – so I've uploaded two photos to illustrate:
How do I repair those cracks? Firstly, what's the best thing to fill them in with? Secondly, how do I get that filler to not fall out while it sets?
From the pictures it looks like the cracks may only be in the stucco, and the underlying structural wall may be unaffected. It's hard to tell without actually inspecting the wall, but my guess is that these cracks are only skin deep. However, you will want to treat them to prevent them from spreading.
Here is a good article about Cracks in stucco.
Here are some excerpts from the article.
All buildings are subjected to a variety of stresses in various forms and this stress is often transferred to the plaster stucco membrane.
Stucco is not and never was intended to be a structural material.
Cement stucco is a relatively thin, brittle shell over a framed structure and can crack if the stresses are transferred and overcome the strength of the plaster membrane.
SHRINKAGE STRESS
All Portland cement shrinks as it cures. Controlling and minimizing that shrinkage is critical to minimizing cracks
Shrinkage cracking tends to have a map-like cracking pattern.
OUTSIDE SOURCES
Structural loads, lateral force racking, thermal changes, wind, lumber shrinkage and seismic events are all examples of outside sources of stress.
HOW HARMFUL IS A HAIRLINE CRACK?
a hairline crack does not automatically mean the stucco is faulty, failing or will not function for the service life of the building.
MAKING REPAIRS
Once the decision is made to make repairs, there are several options.
Option 1: Treat the joint with the same finish material.
Option 2: Paint the wall or ceiling after treating the crack with an acrylic paint or paint designed for stucco.
Option 3: An elastomeric paint coating.
Option 4: Recoat the wall from architectural break to architectural break with the same finish material.
Option 5: A new basecoat and mesh over the wall area.
We had an almost identical situation in a former garage that we refinished to be an office. Our contractor suggested this and we liked the result: he installed a piece of wood about an inch out from the concrete, putting insulation between them and keeping the wood a consistent and level height - a little higher than the concrete. I can't remember if it was pink fluffy insulation or spray stuff. Then a shelf about 6 inches out from the wall - nice and level by being a bit up from the concrete and supported by the vertical wood, and there's insulation under the shelf too. The whole thing is a good looking clear pine and is well varnished.
Looking from the side gives an idea of the distance from the wall:
The shelf runs around the entire room and is remarkably useful for something so low. It hides all the lumpy bumpy aspects of the concrete and while it's not something you see everywhere, no-one has ever mentioned it so it can't be that unusual.
Best Answer
You may need to approach this with some caution. It looks like the reinforcing steel is corroding from the picture. When this happens the steel expands and causes the concrete cover over the steel to spall off. Once the reinforcing bar looses its cover the rate of corrosion will increase and the bond between the steel and the concrete is substantially reduced.
The problem is that just covering up the steel with a crack repair mortar may not fix the corrosion problem and either another section of the concrete could spall off or the repair mortar could spall off. I would suggest you get it looked at by a specialist. It doesn't look like it is in imminent risk of failure but just covering up the cracks may mean that you are hiding a long term problem.