Expert: Bruce E. Johnson - 1/21/2011

Question
QUESTION: Hello Mr. Johnson,

I'm having a kitchen addition built on my home.  Unfortunately, my contractor has prolonged this process for the past 6 months and we are now only in the foundation stage during this winter.  So far, the cement blocks have been laid but the tar(waterproof) has not been laid on.  I am told that the blocks have to be completely dry in order to put the tar on.  I live in NJ and we have had unpredictable weather.  Right now there is snow that has been sitting on the dirt within the laid out blocks.  As it melts the water is inside the 12X16 area.  I have two concerns: I am aware that the cement blocks cannot be placed under freezing levels.  The day they put the blocks up it was 36 degrees and they finished late that evening and did not put a tarp or any covering.  That evening the temperature went to 28 degrees.  They said they used some sort of antifreeze  but ran out at some point so some of the batches of mortar did not have it.  The following 2 days the temperature was rising and went up for 39 degrees.  Should I be concerned about the strength of the blocks due to the weather issues and them having ran out of antifreeze?  My next concern is that we have been getting snow that's melting into the trench and it cannot be absorbed into the ground since there is cement underneath(the footing).  Will this affect the strength of the foundation and should I be worried about infestation due to the water sitting in the trench like termites or anything else that might affect my home?  I worried that due to these issues, regardless of how well he may finish the project, that the foundation being the most important part of the home, will have issues in the future.  I appreciate any advice you can give me and I thank you for taking your time to help me!

Dina

ANSWER: Hi Dina, concrete is very sturdy and capable of withstanding a variety of weather conditions.  If the water in fresh concrete freezes it can affect the strength of the concrete and in severe cases cause it to fail completely.  However it takes a pretty strong freeze to cause this to happen since concrete creates its own heat during the "setting" process.  It is always good to cover and insulate fresh cement or concrete during long periods of freezing.  If the concrete or mortar has been frozen it becomes crumbly and doesn't hold together, it loses its adhesion to the aggregates.  That said, I have no way of looking at the product and making that determination.  An on site engineer would have to make that assessment.  

Cured concrete is generally not affected by water.  It is used to build boats even.  So I wouldn't be too worried about it getting wet or being under water for any period of time.  I agree with your builder that the foundation wall needs to be dry for the waterproofing to take place.  This is an important aspect of your project and it needs to be done properly with a footing drain to keep water from building up around the finished foundation wall.    It is always reccommended that termite pretreatment take place prior to the concrete slab being poured or prior to the floor system being installed.

I hope this information helps please feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com

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

QUESTION: Hi Mr. Johnson,

Thank you for your quick response.  As per your answer with regards to concrete, is there any way to find out if the mortar/blocks are not sturdy enough.  I've heard stories where a year or two from the finish of a project, homeowners find cracks in the foundation.  Is there any way to spot this before, ie during the construction process?  

Also you mentioned that there should be a footing drain to keep the water from building.  There is none at the moment and therefore, all the water melting from the snow is sitting on the lower levels of the foundation wall.  Do you think this will affect the quality of the wall or just the time it takes to evaporate, for the tar to be placed as it needs a dry surface.  

Lastly,(I promise), do you think it is wise/beneficial to have the area pretreated now after the job has begun?  I bought my home a 1.5yrs ago and we had an inspection that didn't show any termite infestation.  I'm just not sure if with this construction and the prolonged period of time it has been taking, if I should be worried about this.  I thank you again for your time!

Dina

Answer
Hi again Dina, concrete is concrete it is probably going to crack.  That's the nature of the beast.  How severely it cracks and if there are signs of separation or settling, unevenness is more of a concern.  This is why we put rebar and wire mesh into it.  As far as the water sitting in the ditch.  When the weather dries out the remaining water can be pumped out so the ditch can dry properly.  I mean what else can your contractor do at this point?  As I mentioned earlier if the Termite pretreat was done prior to the slab being poured you don't need to do any more.  But if your floor system is wood then your pretreatment of the ground under the crawl space should be done just prior to the floor construction..I hope this information helps please feel free to write again as needed sincerely, Bruce e Johnson.  Bejohnsonconsulting.com