Helping a customer with a bad basement floor
Choosing a reputable contractor for your new concrete needs or repairs, pays big dividends in the end. A careless company that uses poor practices can cause numerous problems from a ugly driveway to many thousands in repairs, or god forbid a rip out and replace! Even worse, sometimes issues do not appear for years.
Last week we were called out to a Madison County home that had just recently had a new basement floor placed. The slab had numerous issues and the home owner needed options on how to proceed.
As our team is professionally trained through organizations like the American Concrete Institute, we looked to the standards for the evaluation of Concrete and noted the following.
Here we see piles of rock, and concrete, and the area near the walls rough and higher than the rest of the floor.
Piles of dust were also around the floor. Dusting is exactly how it sounds, regardless of how many times the floor is swept, vacuumed or washed down the slab continues to produce significant amounts of dust.
Water sprayed on the floor shows the hills and valleys (bird baths as we say in concrete lingo).
The contractor placed concrete over the drain and sump pump. Unfortunately we had to break the floor to locate them.
Other issues to take note of are the lack of control joints around columns. There is a lack of expansion foam between the walls and floor and columns and floor. If the floor expands or contracts due to weather, cracking will likely occur here or at the columns. We see signs of water intrusion around the walls. And other surface defects like aggregate pops.
Exposing the drains, it became clear the soil was not compacted, a subgrade of gravel was not placed and no moisture barrier was laid.
Why is this happening?
Firstly, judging by how out of level and rough the floor is, we can determine the contractor was inexperienced and lacked knowledge of the correct procedures for placing concrete.
Secondly, from experience we can tell water was added to the mix in the truck then the concrete was finished incorrectly. This incorrect practice traps water at the top layer making it weak and prone to a number of defects. Worst of all, the concrete has went through segregation/stratification (i.e. the individual components did not bond and became separated) and thus much weaker.
Testing and verification
From the above observations, we can tell that this 3 week old slab is distressed and deteriorating.
Striking the slab in random locations lightly with a hammer we hear a “dummy sound” indicating there are cavities below the floor or the surface will soon delaminate (come off).
This test also revealed that some rebar is extremely close to the surface and will likely be visible if no mitigation is put in place. Near this area we also found signs of soil pulled up and inside the concrete.
Applying water and rubbing the surface the mortar past is dusting completely off leading to an exposed aggregate look.
The Fix / Conclusion
The home owner chose to perform some of the recommendations we gave him and we patched the floor drains.
Our recommendation to the home owner was to try to power wash the slab to remove the surface mortar. The slurry should be wet vacuumed up and not allowed in the sump pump drains. A chisel and hammer could be used to remove some of the wall area heights and worst case a grinder to bring those heights down. After this is complete, apply a densifier. Finally a whole host of options like surface levelers could be applied for a nicer finish.
Our advice to you, Central Kentucky, is hire a reputation concrete contractor and get the final product you want.
Felice Construction