# Drain Tiles, Gravel/ no Gravel?



## concretemasonry (Oct 10, 2006)

Usually, just a sock with will plug if the natural soil is easily erodes - like silt, silty clay. 

The ideal is a well graded range of clean sand and rock. The fill should also be 6" below the pipe. With the right material, a sock is not required, but some people use them.

If you just use 3/4" rock and a sock, the system may work for a while, but the voids in the rock can fill with silt over time.

The blend of CLEAN sand and rock keeps the water velocity down and slows the erosion and flow of silt.

The real hidden value of a properly installed drain tile project is that it keeps the moisture content of the soil lower at all times, so there is not a big surge of water in the system from surface water immediately after a storm/melt. - It drain water out all the time and keeps the local watert able down.


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## jason h (Apr 7, 2008)

our company only does wood foundation, part of the system is 1 to 2 foot of pea stone covered with plastic or felt paper then back filled with dirt. the plastic protects fine particals ( clay ) from migrating into pea stone once the soil settles the plastic no longer has a use.
if you are in good drainable granular sand , you do not need stone at all. install drain tile around all of basement and run to daylight( some where lower than your footings ) are you in clay?


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## B Parker (Mar 25, 2008)

Yes, I'm in Southern Indiana, A good amount of clay. I am on a hill, so the sloping to daylight will not be a problem. We had never seen a drop of water in 5 years of living here until we got the 8-12 inches in a 24 hour period about 2 weeks ago. then our basement took on quite a bit. I'm trying to make sure this doesn't happen again. Pea gravel is what is needed to lay over and under the tile? Is the black stuff with the sock on it a good idea?


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## comp (Jan 14, 2008)

B Parker said:


> Yes, I'm in Southern Indiana, A good amount of clay. I am on a hill, so the sloping to daylight will not be a problem. We had never seen a drop of water in 5 years of living here until we got the 8-12 inches in a 24 hour period about 2 weeks ago. then our basement took on quite a bit. I'm trying to make sure this doesn't happen again. Pea gravel is what is needed to lay over and under the tile? Is the black stuff with the sock on it a good idea?


yes on the black sock,,also part of the water problem may be from the quakes we had(hairline cracks),,,,brother had to add a sump in his walk out basement in Newburgh,,,


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## jason h (Apr 7, 2008)

where did you notice the water coming in from?
where flor meets walls, cracks in walls,
misc spot in middle of walls?


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## B Parker (Mar 25, 2008)

In a corner where the floor meets the walls


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## jason h (Apr 7, 2008)

getting pea stone and drain tile around your basement will definitly help, unfortanitly you need to dig down to your footing. being on clay, water will always follow the clay bed. theres no way of knowiing what they did below basement floor when it was built. so, adding perimiter drain will be most help for the money.
hopefully you dont have to much landscaping to ruin 
good luck


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## Termite (Apr 13, 2008)

Gravel for sure! It is a good idea, and is required by the code.


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## B Parker (Mar 25, 2008)

Pea gravel? Is there a difference in Pea stone" and "Pea gravel"?
I have heard both terms. Concretemasonry refers to 6" below the pipe, is it also advisable to go over the pipe with the pea gravel?
I am assuming that the 6" below is 6" below the footer? the pipe is supposed to be lower than the footer correct?
Thanks to all for the help


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## Termite (Apr 13, 2008)

The IRC code requires that the gravel be one sieve size larger than the holes in the drain pipe. Pea gravel will likely work fine, but you might consider something slightly larger, like 1/2" clean.

Be sure you don't use something like AB3 or road base that has a lot of fines in it, which will harden up like rock. Sounds stupid, but I've seen it done.


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## wiz561 (Nov 11, 2008)

Thanks for this post, it helped answer part of my question.

The other question I have is that if you install the corrugated drain pipe with a sock on it and backfill with gravel, do you have to put fabric on top of the gravel before you backfill with soil? It makes sense so the gravel doesn't get the dirt you backfill with....but then again, is it just redundant?

thanks!


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## benjamincall (Apr 25, 2008)

Have you seen these?:

http://www.lowes.com/pd_308700-676-...d=-1&storeId=10151&ddkey=http:CategoryDisplay


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## wiz561 (Nov 11, 2008)

*cool*

That looks pretty cool... A different idea. I like it.

However, I'm just asking because we're building a house and the builder is using the corrugated slotted drain pipe with a sock around it. I'm assuming they will backfill it with gravel. I'm just wondering if some sort of fabric is required by code on top of the gravel. 

Thanks!


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## benjamincall (Apr 25, 2008)

IRC R406.4.2 discusses perimeter drains in detail. 
Here's a link to the 2006 IRC, New Jersey edition:

http://www2.iccsafe.org/states/newjersey/NJ_Residential/Residential_Frameset.htm

Chapter four discusses foundations. You'll find 406.4.2 on about page 86.


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## wiz561 (Nov 11, 2008)

In the 2009 IRC, it says the following... It's around the part "...be covered with an approved filter membrane material". Just looking for some clarification.

Thanks!



R405.1 Concrete or masonry foundations. Drains shall be provided around all concrete or masonry foundations that retain earth and enclose habitable or usable spaces located below grade. Drainage tiles, gravel or crushed stone drains, perforated pipe or other approved systems or materials shall be installed at or below the area to be protected and shall discharge by gravity or mechanical means into an approved drainage system. Gravel or crushed stone drains shall extend at least 1 foot (305 mm) beyond the outside edge of the footing and 6 inches (152 mm) above the top of the footing and be covered with an approved filter membrane material. The top of open joints of drain tiles shall be protected with strips of building paper, and the drainage tiles or perforated pipe shall be placed on a mini- mum of 2 inches (51 mm) of washed gravel or crushed rock at least one sieve size larger than the tile joint opening or perforation and covered with not less than 6 inches (152 mm) of the same material.


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## benjamincall (Apr 25, 2008)

The section of the IRC I referenced above DOES seem to mention covering both the perforations of the drain tile and the "drain." The drain consists of the gravel and may or may not include drain tile: "Where a drain pipe or perforated tile is used . . ."


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## wiz561 (Nov 11, 2008)

thanks for the response.

Sometimes these codes are a little confusing.


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## Daniel Holzman (Mar 10, 2009)

The purpose of the drain tile is to maintain the groundwater table lower than the basement floor slab. In some cases, the footer is considerably deeper than the slab, for example a slab on grade design with footers around the perimeter. There is no reason to place the pipe more than 6 inches below the bottom of slab, the goal is to keep the slab dry, NOT the footers.

The purpose of the clean gravel (or crushed stone) is to provide a path for the groundwater to enter the perforated pipe. That is why the gravel is installed wider than the pipe, below the pipe, and above the pipe. The purpose of the fabric is to protect the gravel from entrance of fine material, hence you need to wrap the gravel with filter fabric. Wrapping the pipe is unnecessary if the gravel is surrounded by filter fabric. Wrapping the pipe alone does little good if the gravel becomes choked with fine material, since the groundwater will be unable to percolate freely through gravel choked with fines, and your pipe will not effectively collect water.

I prefer to design the system to bring the gravel up to within a foot or so of the surface, that way you can collect surface water and direct it downward to the drain. If you have sandy or gravelly soil, this is not necessary.


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## Gary in WA (Mar 11, 2009)

http://www.servicemagic.com/article.show.Foundation-Drainage.13702.html

Be safe, Gary


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