Originally Posted By: dhartke This post was automatically imported from our archived forum.
Last week I inspected a 3 year old home built on a concrete slab that has a tornado shelter beneath it. The shelter is 6’ X 12’ X 4’ high. Entrance is by a solid trap door. The only ventilation is by a 4" PVC pipe that penetrates one wall and terminates in the attic. The walls, floor, and ceiling are poured concrete. Perimeter drainage is adequate.
The floor is covered by 1/4" or less of water and the walls are all damp (looks like concrete when the forms are first removed), increasingly the closer you get to the floor. No obvious isolated point of water entrance or cracks or honeycomb concrete. I reported "the shelter is damp" and "the owner states it has always been damp" and "UGL Dryloc may prevent further water seepage".
The buyer has requested a cost estimate to apply UGL Dryloc. I now wonder if indeed the dampness is from condensation instead of seepage. The air is stagnant except for the 4" pipe vent. Can condensation occur to this extent in an almost air stagnant space? Can the concrete walls allow the transfer of that much water?
Please advise.
Originally Posted By: dhartke This post was automatically imported from our archived forum.
Thanks for the reply Jerry.
OK one must first determine the source of the water. I would do this by drying the shelter, taping a piece of plastic to a wall (sealing around all edges), close up the shelter for several days, return and see which side of the plastic has collected the water, concrete side, air side, or both.
Let's say only the air side turns up wet - condensation. Remedy? Insulation, ventilation, temporarily closing the vent pipe, ventilating also the solid entrance hatch, insulating the walls or ceiling or both, or none of the above?
We have tornados here every year but very, very few specialized shelters. Personally I'd rather be wet than dead but a dry shelter would be nice.
Originally Posted By: jpeck This post was automatically imported from our archived forum.
David,
Either way (at this point) the easiest remedy is probably adding mechanical ventilation. Either cause indicates something was not done right, and that "something" is likely expensive to correct (it's outside the shelter walls).
Let the moisture in, ventilate it out, set the exhaust fan on a timer. Try running it 2 hours a day. Longer if needed more, less if not needed as much.