Hi, we had an internal foundation drain installed and with that a ‘miradrain’, which is basically a dimple mat that extends up the wall to channel the water in to the drain from the wall. While the wall does not actively flood out, there is some dampness and the idea WAS to install a vapor barrier on the roll and tuck it into that drain, so that moisture would just roll down the wall.

Fast forward a few weeks and after speaking with contractors:

a) we will just be painting the wall with a drylock or similar;

b) contractors all warned us that radon would now be a problem because of the 1″ exposed gap around the perimeter and also a probkem where our dehumidifier will have to run fairly constantly to remove the damp air rising from that joint.

Their recommendation was to just chop off the dimple mat flush with the floor (or slightly lower) and then fill in the crack between the floor and the wall. When we moved in our radon tested at just below the EPA recommendation

Some photos:

https://www.dropbox.com/s/s2tzzx4j0o…11339.jpg?dl=0

https://www.dropbox.com/s/zjdpvh79eefqejr/IMG_20170624_111353.jpg?dl=0

Question: What material should I use to fill the gap? Standard concrete such as quikcrete https://www.hardwarestore.com/650542…ix-1101-110160 ? Or will that crack at this joint? Should I be looking instead at some form of expansion resistant concrete or speciality filler? Concrete looks cheap, but want this done right.

We have got in touch with a radon contractor to come out, test and remediate if necessary. He quizzed me on the drain system and told me to remove that dimple mat and fill in the crack also.

I have approx: 125 feet long x 3 inches deep x 1 inch wide.

Thanks