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cutting concrete

My house's crawlspace has standing water after rainfall, with persistent moisture despite vinyl vapor covers on the concrete floor.  The water is in one area only, about 15 feet in diameter.  I had a contractor cut a 15" by 12" hole in the concrete for a sump pump, which works well, but not all the water on the floor flows toward the pump.  I have a 12" circular saw; may I use a 12" concrete saw blade to cut radial grooves in the concrete to lead the water toward the pump?  Should I rent a concrete saw or would my circular saw suffice?  Do I cut grooves one inch apart (say), and then chisel out the concrete between the grooves to make a flowpath?  What do you recommend?

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Posted 2011-03-28T14:12:35+0000  by wsj28 wsj28





Hello wsj28 and welcome to the community.


Wsj addressing the problems with your crawls space and which steps to take greatly depends on the type of the crawlspace that you have right now.


There are two different types of crawlspaces; vented and non-vented or encapsulated (conditioned).


Vented crawlspaces   have side vents installed and allow cross air ventilation under the living areas.


Idea of the vented crawlspace is to separate the above living areas from the crawlspace (outdoor conditions) with insulation materials and provide a fresh non damped air to the crawlspace in order to control moisture levels.

This is not really a best practice and nowadays builders are turning more and more towards non-vented crawlspaces although there are some exceptions for the areas with a high Radon levels.





I don’t want to get in to the details but basically studies shown that exposing structural elements of your home to the outdoor conditions and pests created some serious problems.


Vented crawlspaces should be constructed just like mini basements.

Walls need to be insulated and floor needs to be covered with a vapor barrier.

Insulating ceiling it's not needed being that idea of the non-vented crawlspace is to be a part of the conditioned space -conditioned crawlspace.


In addition to insulating walls there should also be an air circulation in between living areas or above conditioned and a crawlspace to eliminate moisture buildup.

Flows of 50 CFM per 1000 square feet are recommended.


Now, let’s go back to your questions.


Persistent moisture


This is definitely caused by a water penetration but could also be caused by a improper crawlspace design.


In other words having said that you have a concrete floor and a vapor barrier I’m going to assume that you have a conditioned crawlspace.

With a conditioned crawlspace walls should be sealed and insulated with vapor and non-water sensitive insulation from outdoor conditions.


Anything different than above described could create moisture problems.


Cutting a grooves in the concrete


Technically you could cut the grooves and make a flow path as long you don’t disturb the structure of the slab.


In order to make a flow path  you may need to cut grooves that are deeper than the actual thickens of the slab in order to achieve flow able pitch.


I would recommend something much better and that is to add a overlay over a vapor barrier.


Simply add a layer of concrete over the low area and direct the water towards the pit.


This way you will keep vapor barrier protected and in place and at the same time you can create desired slope.


I'm not sure what type of pit did you contractor put ln but it should be perforated to allow under slab water to drain in and partially accommodate for not having drain tile.


When it comes to using a circular saw I would say its fine as long the RPM,s on the saw do not exceed what is specified on the blade itself.










Posted 2011-03-28T17:08:50+0000  by George_HD_CHI
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