Q: If my initial grouting estimate was between 350 to 450 cu. yds., and only 190 cu. yds. was pumped in does this seem to be suspect or does sometimes the job only take about half as much grout as estimated?
Very good question. When engineers devise a grouting plan for a property, they try to use their experience and education to predict the amount of grout a house will need. They often will even look for other grout jobs performed nearby to try to determine how much grout each of those homes took. They try to base the grout numbers on several factors such as the depth of the limestone, the size and number of cavities and the loose nature of the soils. Ultimately, these numbers are noting more than an educated guess. Typically engineers will tell you whatever they estimate could be up to 30% higher or lower. Sometimes it can be even more. We had a client in Ocala with a confirmed sinkhole. The engineer estimated it would take 250-350 cubic yards of grout to fill the voids. This house actually ended up taking nearly 1,110 cubic yards of grout. This is an extreme example but it does happen. Once they start pumping the grout in, they can’t really just stop once they reach their estimated number. They will typically keep pumping until they reach a certain pressure on the gauge or when the house starts to be affected. More or less grout doesn’t necessarily mean the engineer did anything wrong or that you should be worried. It is almost impossible to predict how much it will take. If anything consider the fact that it took less grout as a sign that maybe the raveling soils weren’t as bad as initially predicted.