Expert: Dan Griffin - 1/1/2009

Question
QUESTION: Your question was

Hi Dan,

I am building an addition to my home. At the connection with the old basement foundation and new crawl space foundation is water seeping in. See these
pictures
http://picasaweb.google.com/lh/photo/NEjZ8nHwV_U1RUz5Knoyug?feat=directlink   
and  http://picasaweb.google.com/lh/photo/F4REpZsI1zt5yDlBz31v0g?feat=directlink

The builder has put twice a concrete patch on the inside of the leaking corner, but some water still seeps true.

Should he have done more to waterproof this corner from the outside like an asphalt membrane?  And since he is still working on the site, should and must I insist that he takes up part of the patio (after the winter)and digs out the corner and does a better waterproofing job on the outside.
Thanks,
Bert Schmitz




ANSWER: Bert, it looks like a first class addition and the work I can see appears well executed.  I assume your builder installed a french drain around the addition to move water away.  The fact that you have a problem at that point worries me - I wonder if the existing had a French drain, if they were tied together, if the water is following  the old footing  and not making the turn.  It does surprise me that a better effort was not made to waterproof a cold joint.  I assume it was doweled into the existing footing, etc.  All good water/damp proofing is done on the outside.  It would be a shame to break uut a new patio to execute.  The patio should have good pitch away from that problem corner.  Exterior flat work should fall a 1/4" per foot.  Was the dirt under the patio well compacted? or is the loose fill at the new foundation allowing water to migrate back to the problem?  Expansive concrete products like "water plug" would not be my first choice.

Now let's worry about possible solutions.  If water seems to be coming from patio and up, and the patio has the correct pitch so that water is not standing or running toward the problem corner, perhaps sealing the joint between the patio and the foundation wall will stop water from getting to the problem.  Only pavement sealing grade urethane or Dow corning 795 caulk should be used.  I am not strongly in favor of this solution.  There is a family of concrete sealers that are expensive, but work.  Look up hydophilic concrete sealers.  The one I have used is  from "mountain grout"
http://www.mountaingrout.com/mggelfoam.htm
These are meant to drill from the inside in the crack/joint, wet everything, inject the polyurethane with a pump.  It seeks water and grows.  We have sealed several long term leaks that  did not lend themselves to excavation on the outside.  The exterior approach is still the best long term solution.  Most water problems are cured by good exterior grading, routing and diverting roof water with gutters and long down spouts, and avoiding planting beds along the building face.



---------- FOLLOW-UP ----------

QUESTION: Dan, thanks for your answer.  There is no french drain around the existing house nor around the addition because it is to close to the septic tank. The builder has build drains under the addition and they are connected to a sumppump in the existing house. I think the problem is surface water that comes between the patio and the foundation and seeps through the cold  joint. I think your proposed solution as to seal the joint between the patio and the foundation seems the most practical special since a step from the house to the patio is going to be build there, see the second picture. My question is if water still goes through the cold joint but stays behind the patch for the moment, will freezing eventually cause the patch to let the water through.
Thanks again and have a Happy New Year.
Regards,
Bert

Answer
If you actually get water holding in the joint and it is allowed to freeze, it can move the addition.  Ice expands as it freezes and it is amazing how strong the force is.  It would be best to either not let water get there, or let moisture on through.  I wouldn't worry about it  too much, I asuspect the crawl space will stay above freezing on its own.  The cement based water plug is porous enough to allow moisture on through.