One year ago, my fiancé and I purchased a home and immediately began renovations. One of our last projects was to remove the floor joists from a 12x20 room addition that was built on a very low crawlspace (16” at the highest point) and install a 5" slab. This would solve problems with access for inspection of the crawlspace as well as some critter and moisture issues - not to mention the passive solar benefits (south-facing room)as well as better insulating properties. I performed all of the prep work myself, including a layer of compacted crushed stone for the sub-base, a layer of small river stone for the base, 4” of rigid XPS for insulation, and 6 mil vapor barrier. The plan was to hire a contractor to pour and finish the slab into a smooth surface appropriate for decorative staining.
A few days ago, our contractor showed up for the much anticipated pour. The results were undesirable at best – deeply disturbing would better describe it, especially considering the amount of work my fiancé and I put into prepping the site. At the end of the day, we were left with a slab with spalling, discoloration, & rough patches and with areas of surface peeling so deep that the aggregate materials are visible.
I am writing today to ask for expert advice on what can be done to remediate this problem. Specifically, short of jackhammering and removing the slab, can it be resurfaced in some fashion to make it smooth and suitable to accept a decorative stain? Could I grind and polish or apply some sort of self-leveling product that will last over time? Perhaps pour a thinner topper slab to cover it? I realize that to answer these questions, more information is needed, so here are some facts about the day as well as some images of the problem:
FACTS:
-The problems were visible immediately after the pouring and finishing.
-Large areas (spots up to 6” in diameter) of the smooth surface layer are peeling away, exposing the rough aggregates beneath. There are some areas where peeling has not yet occurred, but you can tap on it and it has a loose sound like dry paper… a tap with the blunt end of a screwdriver and the surface of these areas will pop off, exposing the aggregate as described above.
-There is discoloration throughout, especially around the perimeter of the room, giving a picture frame effect. There is also a discolored area where the mechanical trowel was left sitting for a period of time, and outlines of all four trowel arms are clearly visible.
-There are raised areas where concrete was added to pitted areas – an obvious post-finishing attempt to smooth over problematic areas. These are not only raised but discolored and rough.
-Despite precise calculations on the amount of concrete needed, as well as a 10% addition to that estimate, the truck ran short of material near the end of the pour. A helper ran and purchased bagged concrete, 8 bags of which were used to finish the job. The contractor cited this as well as what he said appeared to be inconsistencies in the concrete viscosity at different stages of the pour as indications of a bad batch of concrete, which caused these problems. My research has led me to believe is more likely installer error, but I welcome any thoughts on this as well. The area where the bagged concrete was poured is actually one of the better looking areas of the slab!
-There are areas where it looks as if there was no troweling performed and other areas where trowel marks (ridges and gouges) are very conspicuous.
I would like to thank in advance anyone who can provide insight into not only what may have happened here but, more importantly, what can be done to give us a smooth finished surface at least somewhere close to what we were wanting and what we were promised. To do this slab, we worked very hard and used some of our very last funds that were set aside for renovations when we purchased the home. This has been so disappointing and inconvenient, and any advice would mean the world to us! (See images attached) |