Underground Plumbing, Gravel, Floors fghgfd We had fun one evening "laying out" the rooms in the basement! Now that there are walls, we can feel things starting to take shape! Aug 9 - Underground plumbing and first layer of gravel are in. 16 Aug - Part of the pink styrofoam insulation is in. On top of that will be a plastic vapour barrier sheet then the cement slab. Aug 31 - three guys came to do the slabs (main in addition basement, storage room under existing bedroom and small slab in new back entry). They worked all day and were amazing. The floors are great! Didn't get their names or the company they work for, but they definitely know their stuff! The space under the existing bedroom and the new back entry beyond. This is before the final polishing work was done. Floor in the addition basement before final polishing.