Foundation Drains

Footing Drains Keep the Basement Dry from the Outside

Worm's-Eye View

Footing-drain problems are expensive to fix

Building codes require perimeter drains around the outside of basement footings. They are not difficult to install properly before the foundation has been backfilled, but they are costly and disruptive to put in after the fact.

As long as you're going to protect the bottom of the foundation of a house from water, it's worth doing right.

See below for:
SOME SITES ARE TOO WET FOR BASEMENTS

Key Materials

Pick the right drain line

The 4-inch black line that comes in coils is cheaper than rigid PVC pipe, but it’s not as crush-resistant, and the narrow slots in pipe walls are more likely to clog than the holes in rigid pipe.

Design Notes

Integrate water-management strategies

The foundation drain shouldn't do all the work. If groundwater is managed well, underground drains become just one part of a bigger system. Carefully grading the yard can go a long way toward keeping water away. Surface drains and gutters can catch much of the water that does reach the house.

Drainwater can work for you. If the grade allows drains to reach the surface, a rain garden might be a good option. Then water isn't just diverted, it also provides valuable irrigation to the landscape.

Builder Tips

Backfill with quick-draining material

It may be tempting to backfill a basement foundation with excavated soil, but it's best to place coarse, granular material like crushed stone or bank-run gravel against the foundation to encourage drainage. A cap of soil with a high clay content near the surface will encourage surface water to flow away from the foundation.

The Code

foundation drain

The Code

Sections 404, 405, 406, and 801 of the International Residential Code (IRCInternational Residential Code. The one- and two-family dwelling model building code copyrighted by the International Code Council. The IRC is meant to be a stand-alone code compatible with the three national building codes—the Building Officials and Code Administrators (BOCA) National code, the Southern Building Code Congress International (SBCCI) code and the International Conference of Building Officials (ICBO) code.) relate to foundations and below-grade habitable space. All code references are to the IRC unless otherwise specified.

Drainage
Concrete & CMUConcrete masonry unit. Precast concrete block used to build walls. CMUs have hollow cores that can be filled with concrete onsite for additional reinforcement. The use of stronger, more lightweight types of concrete such as autoclaved aerated concrete (AAC) is becoming increasingly popular in CMU manufacture. foundations that contain habitable or usable space need drains [405.1], unless there is good natural drainage [405.1X]. Use filter fabric over drain fields [405.1] and at least 2 inches of stone under pipes [405.1]. If the soil is expansive or collapsible, extend gutter downspouts 5 feet from the building or to an approved drainage system [801.3].

Water-proofing, Damp-proofing, & Backfilling
Below-grade basement walls need damp-proofing [406.1], but if the water table is high, use water-proofing instead [406.2]. Parge CMUs before damp-proofing [406.1], and lap and seal all joints in water-proofing [406.2].

Don't backfill until foundation walls are anchored to the floor framing [404.1.7] (except walls supporting less than 4 feet of unbalanced backfill [404.1.7X]).

Illustration: from Code Check Building 2nd Edition. click to buy .


OTHER CONSIDERATIONS

Keeping your basement dry pays many dividends: a dry basement is less likely to have mold, and the house may have better indoor air quality and fewer moisture problems in the attic. If you value these dividends, invest in high-quality, crush-resistant footing drains of an adequate diameter, and backfill the entire foundation with coarse granular material that drains well.

It's better to run footing drains to daylight than to depend on a sump pump. While that may require more excavation, it's money well spent.

DRAWING LIBRARY CONSTRUCTION DETAILS

Basement Water and Radon Pack
Foundations Details

>> See all detail drawings

WHAT'S WRONG WITH THIS PICTURE?

A footing drain the hard way
These workers are excavating to install a footing drain on an older house — an awkward and expensive task. Most older houses on stone foundations were built without footing drains.

GREEN POINTS

LEEDLeadership in Energy and Environmental Design. LEED for Homes is the residential green building program from the United States Green Building Council (USGBC). While this program is primarily designed for and applicable to new home projects, major gut rehabs can qualify. -H ID2 (Durability Management Process) has prerequisites and 3 points for third-party certification of durability processes/practices.

NGBSNational Green Building Standard Based on the NAHB Model Green Home Building Guidelines and passed through ANSI. This standard can be applied to both new homes, remodeling projects, and additions. Under Ch. 6, Resource Efficiency: 4 points for well-designed foundation perimeter drainage as part of durability measures (602.3).

ABOUT FOUNDATION DRAINAGE

Run it to daylight
Wet basements are common. Even some new-home owners complain of wet basements.

If the slope of the building site allows, perimeter drains should connect to solid pipe that runs to daylight. The solid pipe should be sloped at a minimum pitch of 1/4 inch per foot, although a steeper slope is better. If there is more than 200 linear feet of foundation, add a second outlet or increase the size of the outlet pipe from 4 inches to 6 inches.

When there isn’t enough pitch on the lot, the exterior drains should be connected to a sump pump in the basement via a 6-inch line that penetrates the footing near the sump location.

MORE ABOUT FOUNDATION DRAINAGE

Some sites are too wet for basements

Water that seeps through a basement foundation or is forced upward by hydrostatic pressure can be collected in an interior drain system and routed to a sump for removal. However, if you know that groundwater is likely to be so big a problem that you have to relieve hydrostatic pressure with a perimeter foundation drain system and sump pump, you should seriously consider something other than a full basement foundation.

INSTALLING AN EXTERIOR DRAIN

Dig a trench as deep as the bottom of the footings.

Lay filter fabric first. Unroll 6-foot-wide filter fabric along the trench, lapping the material up the sidewalls of the foundation. Spread the excess fabric away from the foundation.

Add crushed stone and pipe. Over the filter fabric, lay a 3-inch layer of crushed stone, and then install the 4-inch rigid PVC pipe all the way around the foundation. The perforated pipe can be installed level. Window wells should be tied to the drain with solid 4-inch PVC. Add crushed stone to a level about 8 inches above the top of the footing, and then pull the excess fabric over the top of the stone and lap it against the foundation wall.

Finish with coarse sand. A 6-inch layer of coarse sand spread on top of the fabric will prevent soil from washing into the fabric and clogging its pores.

INSTALLING AN INTERIOR DRAINAGE SYSTEM

Create a sub-slab drainage field.

Put down an 8- to 10-inch-deep layer of crushed stone before the basement floor is poured so that the entire area beneath the slab drains. Above the crushed stone, install a layer of extruded polystyrene insulation topped with a puncture-resistant vapor barrier, such as cross-laminated high-density polyethylene, which will prevent any below-grade moisture from rising into the basement.

Install an plastic interior perimeter drain.

In most cases, this consists of perforated 4-inch pipe. Proprietary drainpipe systems are also available, usually at a higher cost. All are designed to pick up water where the basement wall meets the the floor and drain it to a sump, from which it can be pumped out.

Put in a sump pump. Water that’s collected on the inside of the foundation is piped to a cavity, or sump, set below the level of the floor. Use a pump that’s automatically activated by rising water to move water outside and away from the house. If local codes allow, the sump can be connected to the sewer system. (A sump pump could be connected to exterior footing drains if they run to daylight away from the house.)

Battery-powered backup pump.

In areas where flooded basements are common, a battery backup system for the sump pump ensures that the system will work when the power goes out. A maintenance or inspection schedule for the sump pump should be included in the homeowner’s manual. Installing a sump-pump pit cover that achieves an airtight seal will improve the home's air tightness and reduce the risk of radonColorless, odorless, short-lived radioactive gas that can seep into homes and result in lung cancer risk. Radon and its decay products emit cancer-causing alpha, beta, and gamma particles. entry.


Image Credits:

  1. Krysta Doerfler/Fine Homebuilding #189
  2. Dan Morrison
Tags: , , , , ,
30.
Mon, 08/26/2013 - 16:36

Response to Michael Shinn
by Martin Holladay, GBA Advisor

Michael,
Around the perimeter of your foundation, you should install perforated pipe. Once that is done, you dig a trench downhill to daylight. In this trench you install solid pipe, not perforated pipe.

The solid pipe can be backfilled with soil from the excavation. There is no need to install crushed stone or sand above the solid pipe.


29.
Mon, 08/26/2013 - 15:44

Edited Mon, 08/26/2013 - 15:49.

Response to Martin
by Michael Shinn

Martin,
I may be using my terminology incorrectly. Next to the basement wall, for 1ft out, and the whole length of the wall I plan on putting gravel up to grade. But what my question was out in the backyard where the drain continues out to the surface, away from the house, should this also be sand/gravel to the surface? Also would just creek sand be sufficient or do I need something else?


28.
Mon, 08/26/2013 - 14:49

Edited Mon, 08/26/2013 - 14:50.

Response to Michael Shinn
by Martin Holladay, GBA Advisor

Michael,
It's your choice. Many builders decide to backfill with soil from the site. Only you can decide whether local conditions indicate that your basement is likely to get damp, and only you can decide whether you can afford to bring in some crushed stone or other free-draining material.

The decision depends on your budget, and whether the investment in good drainage (and the higher likelihood that your basement will stay dry) is important to you.


27.
Mon, 08/26/2013 - 14:42

The pipe is about 4 ft. deep
by Michael Shinn

The pipe is about 4 ft. deep, so now after all the gravel I have about 3.5 ft. to fill, all this needs to be sand or gravel except 6-8 in.? That seems like a lot, especially if I'm supposed to take this all the way out to the surface.


26.
Mon, 08/26/2013 - 14:00

Response to Michael Shinn
by Martin Holladay, GBA Advisor

Michael,
Most of your backfill should be free-draining material like crushed stone, gravel, or sand. The top 6 to 8 inches or so should be regular soil (or clay-rich soil), graded to slope away from the foundation


25.
Mon, 08/26/2013 - 13:50

Sand backfill
by Michael Shinn

I'm retrofitting my 1940s house with this style footer drain and had a question about the back fill. I want to be sure I'm understanding this right before I bury the section I've dug up so far. I made a trench about 2ft wide, all the way down to approx. 6in below the footer. Then I placed a sediment screen, a few inches of gravel, a black 4in corrugated, perforated, sleeved pipe, a few more inches of gravel and another sediment screen. Assuming that's correct the next layer is sand then the backfill I dug out to start with? If so is there a particular grade/style of sand I should be looking for and how thick of a layer do I need?


24.
Mon, 12/06/2010 - 04:33

Response to Peter Mariano
by Martin Holladay, GBA Advisor

Peter,
Q. "A friend suggested having 2-lb closed cell spray foam sprayed over the top of the footings right up to the top of the foundation wall. ...Any issues come to mind; i.e. durability, waterproof, etc?"

A. Closed-cell spray foam can certainly be used to insulate the exterior of a foundation wall. Of course, the above-grade portion of the foundation insulation will need to be protected from physical abuse and ultraviolet light; most builders use stucco.

My guess is that opinions differ on whether closed-cell spray foam alone amounts to adequate waterproofing. You may want to consider waterproofing measures separate from your insulation layer.

Q. "Referring to drawings 1-05002 ... and 1-06001, ... Why does the rigid foam rest on the footing in 1-05002 and not on the footing in 1-06001?"

A. The drawings in our "Strategies and Details" section are not all drawings of the same house. There are a great many ways to approach construction, and our details offer many options. There is no reason to expect consistency from detail to detail. Detail 1-05002 shows a basement with walls insulated with exterior rigid foam. Detail 1-06001 shows a basement without exterior insulation. If you choose to follow the latter approach, the basement should be insulated on the interior later in the construction process.


23.
Sun, 12/05/2010 - 19:18

Closed cell spray foam as insulator and water barrier?
by peter Mariano

We are building a 1500 sq-ft home in CT on the footprint of a uninhabitable 1740 saltbox which was painstakingly dismantled. The site is on a steep slope with high water table and we will have a sump pump in the basement to assist with removal of water from beneath the slab. My concrete contractor usually applies Tuff-n-dri to her exterior foundation walls. I want to insulate the exterior foundation walls with at least 2" of rigid foam.
A friend suggested having 2-lb closed cell spray foam sprayed over the top of the footings right up to the top of the foundation wall. The footprint is only 24'x27' so the price is comparable to having waterproofing and then adhering rigid foam to the walls.
Any issues come to mind; i.e. durability, waterproof, etc?
Secondly, referring to drawings 1-05002 Concrete basement//insulation out//1" rigid insulation, and 1-06001 Foundation perimeter drain//interior and exterior//with foundation damp proofing
Why does the rigid foam rest on the footing in 1-05002 and not on the footing in 1-06001?
Lots more questions coming as we move forward with our first "green" home.
Thank you
Pete Mariano


22.
Sun, 11/07/2010 - 05:44

Edited Fri, 05/13/2011 - 07:04.

Third response to Don
by Martin Holladay, GBA Advisor

Don,
Your suggestion requires excavating a trench down to the depth of your foundation footing. The trench has to be continued downhill, at a slope of at least 1/4 inch to the foot, until the trench reaches daylight, so that any water accumulating in the trench can drain.

Such footing drains are routinely installed in mountainous states like Vermont. If you live in Kansas, "draining to daylight" is probably impossible.


21.
Sat, 11/06/2010 - 19:17

water in cellar
by Don

thank you for your quick response. can i just dig a 6" hole down about 6" below the floor. put some crushed stone in and then put the 3" pvc pipe in. should i go bigger then 3". how far do i bring the pipe above the ground. water will not come out of pipe, but it will relieve the pressure?


20.
Sat, 11/06/2010 - 04:16

Second response to Don
by Martin Holladay, GBA Advisor

Don,
Yes, your proposed solution would work, if the details were correctly executed. Assuming you are working from the exterior, though, it won't be cheap.

There is no reason to excavate 1 foot below the basement floor; a few inches would work. Be sure to include plenty of crushed stone around your pipe; wrap the crushed stone in filter fabric; and run the pipe to daylight. Include a tee with a riser to grade for a cleanout.


19.
Fri, 11/05/2010 - 19:08

water in cellar
by Don

i understand the respose given but since i live in an area that when it rains there is alot of water pressure under my cellar floor, would the 3" pvc pipe inserted in the ground approx. 1' below the cellar floor help me to relieve this pressure thus stopping my floor from cracking


18.
Thu, 11/04/2010 - 03:42

Response to Don
by Martin Holladay, GBA Advisor

Don,
Here are the steps to follow, in order:
1. Adjust the grade around the outside of your house so the soil slopes away from your foundation.
2. If your house is on a hill, make a swale on the uphill side. The swale should drain away from your house.
3. Install roof gutters connected to conductor pipes. The conductor pipes should drain at least 10 feet away from the foundation.

If your basement is still wet after completing all of these steps, it may be necessary to excavate the exterior of your foundation down to the footings, in order to install footing drains, as you suggest. But correct the grading and address gutters first.


17.
Wed, 11/03/2010 - 19:39

basement floor leaks water when there is alot of rain
by Don

could i install a series of 3" pvc pipes around the outside of my my house close to the foundation to prevent this . i would put the pipes down about 1' below the basement floor and cut off pipe at ground level to try to relieve the water pressure. of course i would dig out the holes first i am trying not to put a sump pump in the basement. any other ideas


16.
Thu, 08/05/2010 - 10:22

Response to Andrei
by Martin Holladay, GBA Advisor

Andrei,
You use filter fabric to separate the crushed stone from the backfill. In practice, this will require careful backfilling in small lifts, and it will require some hand work to place the crushed stone.


15.
Thu, 08/05/2010 - 09:42

How would you do it in
by Andrei Sosnovsky

How would you do it in practice -" install clear gravel wrapped in filter fabric at least 1' wide the entire height of the trench'? How would you separate the 1' gravel "wall" that goes up from footing to grade from the rest of the fill?


14.
Mon, 08/02/2010 - 07:30

Response to Junior
by Martin Holladay, GBA Advisor

Junior,
There is an illustration at the top of this page. What type of picture are you looking for?


13.
Mon, 08/02/2010 - 06:27

does anyone have pictures of
by junior

does anyone have pictures of how the system should look like. It's easy to see an example, but sometimes hard to understand and visualize it.


12.
Tue, 07/06/2010 - 11:44

Response to Michael
by Martin Holladay, GBA Advisor

Michael,
1. I'm not sure why anyone would want to install a footing drain without any crushed stone under the pipe. The crushed stone is important.

2. A footing drain will work if the holes face upwards -- it just won't drain quite as well as if the holes were facing downward. If the difference in elevation between upward-facing holes and downward-facing holes is 2 inches, then your pipe with upward-facing holes won't lower the water level quite as much. A pipe with downward-facing holes will drain the water 2 inches lower.


11.
Tue, 07/06/2010 - 11:38

foundation drain
by michael

What if the holes in the pipe were installed up? I was told that because of the soil and the way it was being installed, the holes should be facing up. Reason was because of the high water and the lack of gravel under the pipe. This was to get the water away from and out of the house. With little gravel area around and under the pipe, there was a better chance of keeping the holes clear. Has anyone heard of this?


10.
Tue, 06/29/2010 - 20:47

these clay soils could just
by roel

these clay soils could just be back filled above the pipe that's connected to the gravel system and can simply hold water against the wall, that is why we are recommending you to have the Humidifier Filters attached next to the wall which cause a leak in the foundation of the wall. This is because of the cooling of the water, which also makes the wall weak, and leaves small pores in the wall which cause water leakage.


9.
Wed, 06/23/2010 - 20:51

Perimeter Drainage
by Anonymous

I am having a house built and they just laid the pvc around the home and covered it with stove. I dug down a bit to see if everything was connected and there are no 90's on the corners and the main outlet to move the water away from the house is not even connected. Doesnt sound right.


8.
Mon, 04/05/2010 - 08:52

GBA drawing misleading
by Alan

Thanks Martin. I value your comments. And thanks for posting mine. Yes I see GBA agrees with the "gravel the entire depth of trench" method. But check out your drawing above- it shows mystery backfill above and at grade and the nice gravel backfill is only around the pipe at the bottom. Most builders in my experience are very visual folks and study the drawings and then call the backhoe! A picture is worth a thousand words. I am requesting you guys at GBA either re-draw this misleading drawing or at least label it better to say "only allow max. 6" deep of topsoil above your trench full of clear gravel" or something like that. The drawing doesn't match your top-notch written information. Thanks!


7.
Mon, 03/29/2010 - 09:56

It depends on the tree roots
by Martin Holladay, GBA Advisor

Jacques,
The two main enemies of footing drains are fine silt and tree roots, so the longevity of the system depends on whether the foundation was backfilled with coarse granular material or ordinary soil; the soil type; the rainfall; and the proximity of trees.

If the system is well designed and installed, I'd say the expected lifespan would be considerably longer than 40 years. Installing clean-outs (risers to grade) helps make it easier to diagnose and sometimes fix problems.


6.
Mon, 03/29/2010 - 09:24

foundation drains
by Jacques

Question: what is the durability or useful life expentency of an exterior foundation drain: 20-30 years, 30-40 years ??
Thanks
Jacques


5.
Tue, 03/23/2010 - 09:30

Footing Drainage
by Dave

I read the second comment. Drainage from the roof to the gutters go into a separte drainage system which is installed around the perimter of the building just approximately 2 to 3 feet. This soild pipe drainage systm is for the exclusive use of draining water that runs off the roof, into the gutters to the drain spouts and into this separate drainage system. Anyone, connecting the drain spouts to the footing/foundation drainage system should be shot (pun intended). By doing it right, no problems develop, period.
Further, want to prevent water and moisture into the basement? Before the contractor pours the concrete footing, install 6 mil plastic sheathing on the ground soils. Once the concrete footing and wall is poured and cured, fold up the 6 mil plastic along the surface of the footing up several feet along the exterior and seal the top. This prevents ground water and moiture from wicking up into the concrete through to the interior (plasti poly acts as a barrier) further, this is continuous underside of the concrete slab where 6 mil poly is a standard installation underside the concrete floor anyway. PS: Doing the following with the poly plastic, will eliminate the need to put a small silly plastic pipe in the concrete footing for so-called drainage from underside of the slab.


4.
Mon, 03/15/2010 - 18:00

footing drains
by craig

Backfilling with crushed stone is simply a way of inviting water into your basement. Any backfill soil above the footing drain, in my opinion, should be as impervious or more impervious than surrounding soil. Runoff should be handled at the surface.


3.
Sat, 03/13/2010 - 06:41

See the "builder tips" tab
by Martin Holladay, GBA Advisor

Alan,
GBA agrees with you. Click the "Builder Tips" tab, and you'll read, "It may be tempting to backfill a basement foundation with excavated soil, but it's best to place coarse, granular material like crushed stone or bank-run gravel against the foundation to encourage drainage."


2.
Fri, 03/12/2010 - 22:45

Another problem with exterior foundation footing drains
by Ted Welch

I completely concur with the above posting by Alan.

Additionally, it is not uncommon to find downspouts feeding into exterior perimeter drain systems.
These downspout connections provide an ideal entry point for leaf and twig debris from the homes' gutters. Once down in the drain line this debris accumulates and eventually turns into soil. I've rarely seen an exterior perimeter drain plumbed with appropriately spaced clean out ports. This may be because the drain is installed by the concrete contractor who has done the foundations. There are conscientious builders who install wire leaf guards in the drop tubes at the top of each downspout. Some even create a break between the downspout and place wire mesh over the lead down to the perimeter drain. These precautions are easily dislodged either by seasonal gutter cleaning or by lawn services.


1.
Fri, 03/12/2010 - 22:00

Gravel Fill
by Alan Ostner

I have seen the system fail as drawn. Clay soils backfilled above this terrific pipe & gravel system can simply trap water against the wall underground and cause a leak in the foundation wall. Always install clear gravel wrapped in filter fabric at least 1' wide the entire height of the trench, from pipe up to grade. This disallows the miraculous "water running uphill" phenomena that every foundation wall contractor has witnessed, where underground water under hydrostatic pressure acually travels upward and misses the trench drain at the low point (as drawn) , instead building pressure in the soil against the wall and leaking into the basement.


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