Here in Central New Jersey many homes have basements with foundations constructed of Concrete Masonry Units (CMU)s. CMUs are also called Cinder blocks or just Concrete Blocks. When installing a French Drain in a house with hollow block masonry walls, we put weep holes in basement walls, allowing the drainage to occur. A drain tile or French Drain system will capture the water entering the block system and drain the water into a pit where a sump pump will discharge it from the building. An interior French drain is much less likely to clog than an exterior, partially due to the fact that it is not sitting underneath several feet of soil.
Installing a French drain around the inside perimeter is most commonly done after the house has been built because the hollow blocks are filling with water and leaking into the basement. When your foundation was constructed, tar was applied to the outside of the hollow concrete blocks. The tar is a degradable substance that has a 30-40 year life. Once the tar is gone water leaks into the blocks and must be Wept Out as part of a French Drain system. Most often, this is done in response to a wet basement or right before performing a basement finishing.
How We Install French Drains
- The inside perimeter of the floor is cut approximately one foot from the wall. A trench is excavated and pitched.
- Where possible, the lowest course of block is tapped and bled (weep holes) in order to drain the walls.
- Fully slotted polyethylene drainage pipe is installed and covered with gravel. This pipe meets the requirements for drainage pipe as required by the State Code and the standards for ASTM-F405-74.
- Polydrain wallboard is installed over the bottom of the wall and over the entire trench in the basement.
- The basement floor is re-cemented to its original level.
- To discharge the water, we will install a submersible pump in a covered polyethylene liner.
A competitor’s representative told a consumer that his company always drills weep holes “above the bed joints”
We drill at the lowest course of block. The bed joint is the lowest course of block. The bed joint is the layer of mortar that the first course of block is installed upon. While the term “above the bed joint’ is real, it is almost nonsensical in this context. First, you have the footing, then a thin layer of mortar (the bed joint) then the course upon course of block. YOU HAVE TO DRILL THE HOLES ABOVE THE BED JOINT. There is no other way to do the job. I think this term was given to prospective customers as a form of misdirection because it doesn’t make any sense.
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