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Footer Drain


Jeff Remas
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Jeff,

Be careful with that one. What is the elevation of the floor?

NJ IRC 406.4.2 Foundation drain-"...Where a drain tile or perforated pipe is used, the invert of the pipe or tile shall not be higher than the floor elevation..."

Hopefully, they were planning to remove the debris prior to backfill.

Darren

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I have actually talked to national foundation repair and waterproofing companies that market their above the footer drainage systems. I had always thought that the drainage system at the bottom of the footer was correct, until I considered the folowwing logic.

They say that this is the "clean water" zone. Any water getting to that point will have had to flow upward and is perforated through the pea gravel fill.

One method of footer construction of a crawl or slab is to dig out and pour the footer. After the footer has set-up overnight, the soil inside the "footprint" is removed to a level even with the top of the footer. After the foundation is built the pea gravel is spread out inside the footprint. If the drainage system is placed on top of the footer, any water entering will have perforated through the pea gravel, with the dirt/silt hopefully resisting the flow of the water and staying in place instead of defying gravity and flowing vertically into the tile.

In a system where the soil is removed to the bottom of the footer, even though you still fill with gravel the soil can still flow horizontally into the drainage area, especially with a deep footing, where it actually flows down. This can cause undermining of the floor/footer and even fill the drainage tile with soil. I know that a membrane is usually placed over the tile to prevent soil from passing through, but it may eventually plug and render the drainage system useless. After all, it is still a filter. The job of a filter is to prevent material from passing through. What gets filtered out of the water gets stuck to the outside of the filter and continues to build. Have you ever tried re-using a coffee filter? How many uses do you think you would get before you have it overflow.

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Jon, this is new construction and in my state the IRC applies. Whether it is the old BOCA, IRC or standard building practice, the footer drain should be at the level of the footer (along side it) which should be below the basement floor or crawlspace floor. This is the presriptive code as written as well as common sense. National foundation repair and waterproofing companies are not the authority when a code applies in your area.

Silt socks can be placed over drainage pipes (I prefer black corregated with holes rather than what you see here) however I have talked to several contractors that have one back a few years later and they were blocked from the outside. Nice for french drains, not for the footer.

Eventually all footer drains get clogged even if it takes 50-100 years. The gravel around the pipe along with the geotextile fabric over the gravel should help this situation and protect it. This is still go guarantee if you backfill with a lot of clay for example. Clay can allow water to pool on top giving opportunity for water intrusion into the foundation walls. I have witnessed this problem personally. The clear majority of foundations are damp proofed, not water proofed. Water proofing is a multi layer process or a membrane that is still layered on. Parge and tar is only considered damp proofing.

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Originally posted by Jeff Remas

Jon, this is new construction and in my state the IRC applies. Whether it is the old BOCA, IRC or standard building practice, the footer drain should be at the level of the footer (along side it)

Good point, I did not reference the IRC prior to posting. I was simply going off of a personal conversation with the water proffing company.

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