# Foundation Drainage



## Kearney.200 (Oct 3, 2016)

Can someone give me a good definition of _*filter membrane *_?
and if the drain tile is covered with rock in clay soil do you need to have a " sock" over the drain tile?
2012 IRC thanks


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## ICE (Oct 3, 2016)

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. Perforated drains shall be surrounded with
an approved filter membrane or the filter membrane shall
cover the washed gravel or crushed rock covering the drain.*
Drainage tiles or perforated pipe shall be placed on a minimum
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.
Exception: A drainage system is not required when the
foundation is installed on well-drained ground or sandgravel
mixture soils according to the Unified Soil Classification
System, Group I Soils, as detailed in Table
R405.1.
http://www.erosionpollution.com/geotextile-filter-fabric.html
*
"The top of open joints of drain tiles shall be protected with strips of building paper."  *That sounds like a waste of building paper and I have never seen the use of drain tiles.

As to the sock over the drain pipe, If the rock is wrapped then the sock isn't required.  I usually see the burrito wrap and a sock over the drain pipe.  
*Perforated drains shall be surrounded with an approved filter membrane or the filter membrane shall cover the washed gravel or crushed rock covering the drain.*


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## JBI (Oct 4, 2016)

Filter membrane could be geo-textile fabric (modern method) or a layer of hay or straw (typically minimum 6" thick when applied). The intent is to prevent fine particles of soil from getting into the gravel and plugging up the voids which would restrict drainage.


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## FLSTF01 (Oct 4, 2016)

In this area, we see 4-inch perforated pipe, either black corrugated or white PVC with the holes down, surrounded by 1-1/4 crushed rock and filter fabric on top.  I have not and will not accept "sock pipe" and stone with no additional filter fabric to cover the stone.


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## Pcinspector1 (Oct 5, 2016)

FLSTF01 said:


> I have not and will not accept "sock pipe" and stone with no additional filter fabric to cover the stone.



Why will you not accept the "sock type?" 

Real common in this area.


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## conarb (Oct 5, 2016)

Tiger said:
			
		

> "The top of open joints of drain tiles shall be protected with strips of building paper." That sounds like a waste of building paper and I have never seen the use of drain tiles.



That's because you kids don't know anything, that's all we used until the 60s.  We did put strips if 15# felt over the joints of 12" long 4" terra cotta clay pipe, that was replaced in the 60s by *Orangeburg pipe* (both solid and perforated) and in the 70s by Flex-Drain, good builders still use Flex-Drain or Orangeburg, but perforated PVC drain pipe soon took over being used by the crappy low-cost builders.  

The problem with the 4" terra cotta drain is tree roots or subsidence would move the 12" lengths apart, but it's still better than the PVC crap that totally disintegrates within 30 years.


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## Pcinspector1 (Oct 5, 2016)

conarb said:


> That's because you kids don't know anything, that's all we used until the 60s.



They smoked a little hemp in the "60" too!

Orangeburg, rolled up tar paper, you'd be better off cutting the bottoms of paint buckets out and taping them together end to end with duct tape!

Clay tile, never met a willow tree that did't make the inside part of the pipe its permanent residence.


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## conarb (Oct 5, 2016)

PCInspector said:
			
		

> Clay tile, never met a willow tree that did't make the inside part of the pipe its permanent residence.



While that's true the world doesn't have willow trees everywhere, while the world does have soils everywhere.  Recently I tore down a house to build a new one, in one pier a piece of PVC pipe ran through the corner of the pier, on my first inspection the inspector looked down into the pier and saw it asking what it was, I told him it was an old abandoned sprinkler line from the old house, he said: "Get it out fo there, I don't allow plastic pipe in my town, it just looks bad", I called my foreman and told him to get it out of there, by the time he checked all piers and we returned the plastic was gone and he signed me off.

BTW, I recently read that his town and the highest median house values in the United States *at over $2 million*, maybe it's because inspectors keep the values up?


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## FLSTF01 (Oct 5, 2016)

PCInspector1:  I don't like sock pipe because the filter membrane has a tenancy to clog up quickly with silt.  Builders were trying to argue that no filter fabric was needed on top of the stone because it was already around the pipe.  of course, this left the stone vulnerable to getting silted up which in time, allowed the silt to then clog the fabric around the pipe.  

In a typical installation, the water flows through the stone and the pipe is only there a a backup provision.  Why would we want to allow the primary means of collection and travel to silt up prematurely?   That and I never liked the corrugated pipe to begin with, it is prone to crushing, the interior corrugations catch sediment and impede flow and it is difficult to install with no dips in it.  

Our old code (2009 IRC) used to say that the footing drain system had to be _approved_.  As in approved by the AHJ.


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## Pcinspector1 (Oct 5, 2016)

FLSTF01,

I would think 1-1/4" crushed rock would create a lot of voids allowing silt infiltration to the pipe, would that be true? Here we see 3/4" clean and some times 3/8" chat used to cover the drains. I'm not keen to the chat, tends to soak up water and stay damp where the 3/4" clean rock has some voids. But still we see the sock over the corrugated ABS pipe around these parts most of the time. I have yet to see felt paper being used.


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## FLSTF01 (Oct 5, 2016)

The beauty of 1-1/4 rock is all the voids, and it locks together really well and helps prevent the pipe from crushing.  It's the size they use for septic systems here so it is readily available.  If the rock wasn't covered with fabric, yes, it would silt up quickly.

I'm not familiar with what chat is.


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## Pcinspector1 (Oct 5, 2016)

Chat usually has some limestone dust with it and is similar in size to pea gravel.


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## Rick18071 (Oct 10, 2016)

I would never accept hey or straw. How long do you think it would last?


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## Keystone (Oct 10, 2016)

By today's standards using straw wouldn't seem to fit, it's not a listed product, it's natural, I imagine it's cheaper, etc... However just 10 or so years ago this was the method used by tradesman. 
Personally I would like to see an actual time lapse or study of 4-6 inches straw with felt VS cloth geo textile on durability and function.


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## JBI (Oct 11, 2016)

Rick18071 said:


> I would never accept hey or straw. How long do you think it would last?


If more than 2' below grade, it would last a very, very long time. Aerobic bacteria are not active beyond that depth (not enough oxygen), and they are responsible for much decay. It will partially decay, but not completely.


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## JCraver (Oct 12, 2016)

JBI said:


> If more than 2' below grade, it would last a very, very long time. Aerobic bacteria are not active beyond that depth (not enough oxygen), and they are responsible for much decay. It will partially decay, but not completely.



Yep. 

Ever cleaned out an old barn?  When you get down to the dirt floor and start scooping the po0p out, there's always ancient hay/straw buried under there, and it almost always looks like it was buried yesterday.  It lasts a long, long time under ground.


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## Ryan Matheson (Jan 14, 2020)

It was mentioned above by ICE, the gold standard practice for this application is to do away with using a sock wrapped perf pipe entirely and instead wrap the entire drain AND rock in a "burrito" fashion so that you can ensure you won't be redoing the drainage lines. The following video shows how this can be easily done. 



 . 

Typically you'd want to use something like a 4 oz permeable nonwoven fabric, so that you get both encapsulate the trench and keep it "clean" from the surrounding dirt while enabling it to drain properly. https://www.mainlinematerials.com/p...ric-mirafi-140n-equivalent-5-x-360-roll-hanes

This post is a few years old now and i'd hope that the project went well. For anyone else in a current similar situation hopefully this helps!


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## Mac Moonfire (Jan 16, 2020)

Hi, up here, "we the north" are seeing a typical assembly of 4" PVC perforated pipe as drain tile. wrapped in 6" of 3/4" clean crush or similar material. Geotextile also named "landscaping fabric" protects the integrity of the voids between the drain rocks. Kind of an important role.

The socks are not designed to be installed in silty or clay soils as the small particles will clog the fabric. In the video above it is obvious that the soil has a high content of clay for 2 reasons. 1st, they wish to have a french drain around the yard, it's a clear sign the water isn't draining much. 2nd just by looking at the video you can see the clumps of clay still holding on to the drain. The only place a sock is desirable is in sandier soils to keep the particles from entering the drain or in organic type soil like a swamp or rich top soil.

know your soil!


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## Rick18071 (Jan 21, 2020)

When codes were first started here in 2004 in PA  we use to see a lot of straw but we always rejected it. I haven't seen it for for the last 10 years at all.


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