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foundation drain

dat pe google

DEAR TIM: I have a large fenced yard that is used as a corral for my two very largedogs. Spring rainfall turns the yard into a swamp and my dogs need a bath before theycome indoors. What can I do to dry out the soil? To add insult to injury, water from theyard seeps into my basement. Is there a way to solve both problems at the same time?Meredith R., Des Moines, IA

DEAR MEREDITH: From the sound of it one might think you could saddle up and ride

those dogs! I have seen similar dog runs that turn into a quagmire as the back and forthmovement of the heavy animals churns the wet soil. Fortunately, there is a solution to both of your problems. I can promise a bone dry basement and faster draining dog pensoil, but I can't tell you that the dogs will be lily white after a series of rainy days.

Remember, the holes in the perforated pipe point down. If they point up, they get clogged by pieces of gravel.People all over the USA have problems with yard flooding. Sandy soils found in Florida,the high desert of California, and in the desert southwest are not immune from ponding

after periods of heavy rain. You can effectively drain soil if you understand how water moves through it.

When rain falls from the sky it enters the topsoil. Topsoil consists of small pieces of soil,rock particles, organic matter, water and air. Topsoil thickness varies widely and those people who have clay soils know that the deeper you go into the soil, the more compact itis. In fact, some soils are so dense that they will readily hold water just as a bowl or pot.



As the rainwater enters the topsoil, it begins to fill the space in the soil that just moments before held air. In periods of heavy rainfall all or most of the air is expelled from the soil.Hundreds of thousands of gallons of water can be stored in the topsoil layer. This water begins to move under the force of gravity and the weight of the water within the soil. If the soil is sandy, the water may flow down deeply into the subsoil. But if the soil has a

high clay content, the water actually begins to move sideways through the upper layers of the top soil. Clay subsoils typically have few air voids and these dense soils block thedownward movement of water deep into the earth.

Water, as most things, desires to take the path of least resistance. As it movessideways through most soils, you can intercept it and re-direct it to a low spot on your property. I have dried out many a lot and stopped thousands of basement leaks using alinear French drain.

This drain system consists of a 6 inch wide by 24 inch deep trench that works like a moatto protect your lot and home from subsurface water attack. A four inch perforated drain

pipe is placed in the bottom of the trench. The pipe is then covered with one inch or slightly larger washed gravel to within one inch of the top of the trench. As the water passes sideways through the soil it contacts the gravel. The water decides that it is mucheasier to drop down through the gravel and into the perforated pipe rather than push itsway through the soil.

The trick to trench placement is simple. You want the trench in a location so that itintercepts the water before it hits the house and/or the dog run area. If your yard is on aslope, you want the trench or trenches on the high side of your property. This way youcollect all of the water flowing through the soil uphill from your lot.

The depth of the trench can remain a constant 24 inches as it passes by and around your house. If your lot is sloping, the constant trench depth will create a natural slope to the perforated pipe in the bottom of the trench. Once the trench system passes your home,you can start to make the grade at the bottom of the trench less or even level.

If the bottom of the trench becomes level and your ground is still sloping, the bottom of the trench will eventually surface. Ideally you want this to happen at the lowest part of your lot. The water collected by the trench system is discharged on top of the land only tore-enter the soil on its way to the nearest creek or brook.

Before you install this system be sure to check for underground utilities. Digging by hand

or with a power ditching device can result in serious injury or death if you strike electricor natural gas lines. It is also a good idea to check with your local building department or municipal office with respect to storm water management regulations. Some areas maywant you to pipe this water into a storm water retention basin.

Author's Notes:



October, 1999

Do you wonder if linear French drains really work? Read an e-mail I received from PatJones in Vienna, Virginia:

"A year ago last spring, I called your radio show from my home in Vienna, VA. Idescribed my problem with water in my basement. It was very predictable, every time itrained 2" or more in 24 hours I would get water in my basement. Anyway, you advisedme that a French drain would solve my problem.

"So I rented the ditch witch and got a bunch of friends, following your on-line tips weinstalled the drain. Your tip about the plywood to have the dirt flow onto was a greatlabor saver. We did have a lot of trouble with rocks and tree roots stalling the machine but in the end it was a job well done.

"Of course our work and your advice caused the drought in the Washington, DC area. We

waited almost a year and a half before we got to really test the French drain. However when hurricane Floyd came through and gave us 4" in less than a day and the basementwas high and dry I figured it was worth the drought. Now the neighbors are asking myadvice, and I point them to your web page.

"When we talked you said to let you know how it worked out. It worked out great!!

Thank you very much,"

Patrick Jones

November, 2003

The straw layer mentioned in the column above is not necessary if you fill the entiretrench with gravel to within one inch of the top. The reason is simple: Silt does not passsideways through topsoil. The silt that turns stormwater runoff brown is eroded soil particles that are running in overland flow.

Silt particles get trapped and filtered in the upper layers of top soil. The vast amount of water captured by a linear French drain is water traveling sideways through soil. It isgenerally clear and free of silt. To prove this point, spring water and water taken fromunderground wells is almost always crystal clear. The silt was left behind at the surface asthe water was entering the ground.

June, 2008

You may wonder if my advice is worth anything. Well, read what Jim Sanders wrote tome when he was at the end of his rope:



"Hi, I just wanted to write to give you the results of my "Trench Drain". I have had a wetcrawlspace for 15 years. Water would fill the crawlspace at times, so we actually had todrill weepholes at the base so that it would enter the basement and eventually, the sump pump.

I have tried everything. Several contractors said that the only thing we could do was to bring the water into the house via drainage tile and let it enter the sump pump. Thatwould work, but because I live on a 6' elevation, there is no reason that I should havewater problems. It became like clockwork...when it rained, we would rush home from thelake or wherever we were vacationing so that we could be prepared to start the backupgenerator, in case the power failed. We even had our alarm company put a sump alarm onour system, so they could notify us if we had a power failure. Battery backup was not anoption, because sometimes we loose power for days and during any rain, our sump wouldrun every 7 minutes...just like clockwork.

I found your site and read the article on the trench or French drain. At first, it sounded a

bit like "holistic healing" to me. I failed to understand why a 2 ft. deep trench, 4 ft. awayfrom the house would do any good. How could this simple thing correct an extreme water problem that has plagued me for years, cracked my foundation, settled my garage floor and ruined almost every vacation?

The Linear French Drain trench running from the house. PHOTO CREDIT: Jim SandersI decided "what the heck". I had to dig by hand using a trenching spade and a pick-axe, because the builder back-filled our property with brick and blacktop. It took quite a bit of time. Because the ground level varies so much on that side of the house, I was not able toachieve exactly 2 ft. deep. It varied from 18" to 30" in spots, but the slope was downhill.

The trench is about 80 ft. long. At times, I thought about filling it all in, because I justdidn’t believe that it would work.

I stoned it, put tile in, and filled it with #1 round stone. I socked the pipe just for safetymeasure and I also used geotext fabric on top, so I could cover with dirt and grass. I alsoordered some clay and pitched from the house to the drain.



After a short rain, water is running away from the house. PHOTO CREDIT: Jim SandersResult? For the last month, we have had 7 or 8 torrential rains, the worst of which waslast night. It rained so hard, that our lawn washed out in spots because of the high claycontent. Our sump pump, that normally ran every 7 minutes during and after rain, has not

turned on for 4 weeks. The silt at the bottom of the sump well is now dry and cracking.Our crawlspace has not shown a trace of water or even moisture.

Since I couldn’t see correcting the foundation cracks or the garage floor settling andtilting until I corrected the problem's source, I waited to see if the trench drain workedfirst.

This week, I had a company come in and perform sort of a "mud-jacking" technique onthe garage floor, which worked perfectly. Also, during the past few weeks, I parged thecracks in the foundation.

A dry sump pump. PHOTO CREDIT: Jim SandersI just wanted you to know how this worked. I stressed for many years over this issue andthe solution was nowhere near as difficult as I thought it would be.

As a side note, I went to the end of the drain tile during a hard rain to see what washappening. Water was running out of the drain tile in about the same exact volume that it previously ran out of the weepholes in my crawlspace. This winter will be interesting,



because last year, the ground next to the house was so saturated that during a thaw, mysump would run constantly. I'm guessing that the ground between the trench and thehouse will probably be drier now going into this winter."

- Jim Sanders, Upstate area - New York

Foundation Waterproofing & Drain Tile

SystemsBy Tim Carter ©1993-2011 Tim Carter

2ShareSummary: Exterior foundation waterproofing treatments vary greatly. Most foundationsare damproofed. Drain tile systems, if installed correctly, will keep your foundationwaterproof for years to come. Here are some drain tile installation pointers about

backfilling and preventing ponding.

Related Articles: positive drainage, storm water drainage, French drain

! ! ! See Author's Notes at Bottom of Column ! ! !

Did you know that there is a big difference in exterior foundation waterproofing treatments? I'll bet youthink that your new home foundation has been waterproofed. Yes, you saw that black stuff sprayed on soyou are in good shape. Isn't that right? WRONG! Fewer than 1 in 50 houses in the Greater Cincinnatihousing market have waterproofed foundations. Most are damproofed. What do you think is happening inyour city?

What's the Difference?

Concrete soaks up water. If you place moist earth around an unprotected foundation, your basement will bedamp. Surely you have been in an older basement and smelled this moisture. Older homes rarely had anytreatment on the concrete or stone.

Beginning in the 1950's there was widespread use of asphalt on new foundations. This was hand brushed or troweled onto a new foundation by laborers. The asphalt did a great job of minimizing water soaking intothe foundations. However, it did not possess the ability to bridge or fill a crack which may develop in the

http://www.askthebuilder.com/339_Positive_Drainage_Keeps_a_House_Dry.shtml

http://www.askthebuilder.com/NH011_-_Storm_Water_Drainage.shtml


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http://www.askthebuilder.com/339_Positive_Drainage_Keeps_a_House_Dry.shtml


http://www.askthebuilder.com/619_French_Drain.shtml



foundation. You see, after a period of time, asphalt becomes somewhat brittle. When a foundation treatedwith asphalt cracks, the asphalt cracks too!

Approximately 10 to 15 years ago Owens Corning modified standard asphalt by adding some rubberizedcompounds. The result was a compound that had a certain amount of flexibility. Other companiesdeveloped synthetic rubber compounds that have far greater elasticity than the modified asphalt. Even

before either of these products was available, commercial builders used cardboard panels filled with bentonite for waterproofing. Bentonite is a special natural clay product that swells when wet. Water carriesthe clay into the crack, it swells and plugs the leak! The bottom line is that you can truly waterproof your foundation. It just takes a little homework on your part to select the right product for your particular building situation.

Drain Tile - REALLY Important

If you decide to have your new foundation waterproofed, the company doing the work will most likelyinsist that they install or monitor the installation of your drain tile system. Very few builders that I'm awareof take the time or interest to adequately install drain tile.

Water naturally flows toward your foundation. This is especially true if you live on a hillside or even a

slight slope (which, by the way, most of us do!) Water moves horizontally through soil. Water occupies thevoid spaces between the particles of soil. The deeper you go into a soil, especially if it is clay, the lessspace there is for water.

To make matters worse, the soil that is use for backfill around your house is rarely compacted. When it isdumped around your house it has huge amounts of air in it. This dirt was fluffed up and pumped full of air when it was dug from the ground. It can takes years and years for this ground to naturally compact. In somecases, where overhangs protect the dirt, it may never truly compact. It can always have more air in it thanthe soil that is only 5 or 6 feet away. This can spell BIG trouble for your foundation if it is not waterproofedAND if you have a bad drain tile installation.

From the above discussion, you can see why draintile is important, I hope. The point is this: the backfillsoil has the capacity (because of the large volume of air) to hold large quantities of water. You need tocollect this water rapidly and get it away from your foundation. That is the job of the draintile.

Another Quality Installation

That is a phrase I often used to tease my coworkers after we would finish a task. It was an inside joke.However, the phrase applies to drain tile. You generally only have ONE chance to put it in. It gets burieddeeply. It can clog up if not installed right. It's expensive to redo. For these and several other reasons, youneed a quality installation.

I always like to install the drain tile on the side of the foundation footer. Many builders simplyinstall it on top of the footer. Installing the draintile on top of the footer means that your water table will beat the top of the footer. My method puts the water table about 6 inches below the top of the footer. You

want the level of water as low as possible.

I recommend that the drain tile be installed the day after the footers are poured. I used to help strip theforms and then put a 1 to 2 inch layer of 1 inch gravel along side the outside of the footer. I would theninstall the drain tile continuously around the footer. Finally we would cover the drain tile with 1 inch gravelflush with the top of the footer. This would complete phase one of the operation.

There are advantages to doing the job this way. First, the space between the side of the footer and the wallcan fill with collapsed dirt and/or concrete overflow from pouring the foundation wall. This stuff is tough



to dig out and remove once the basement walls are poured. Besides, it is tough to work in the narrow arealeft along the foundation after the walls are up and poured.

Once the foundation is waterproofed, you can continue the drain tile installation. I recommend that youinstall an additional 2 to 3 feet of 1 inch gravel cover above the footer. On top of this, install tar paper or a6 inch thick layer of straw before installing any backfill dirt.

The elimination of the straw or tar paper is a huge mistake. The backfill dirt is fluffed up. When it gets wet,small silt particles will be carried into the gravel. This will clog the gravel. If your soil has enough fine particles, you may clog your draintile! All of your work will have been for naught!

Seeking Daylight

So where does the draintile water go? Good question! If you are lucky, it drains out somewhere on your lot.Here is what I mean. If you are building on a sloped lot, maybe you are lucky to have enough fall withinyour property line whereby the draintile can daylight. There is no need for the pipe to have a slope. It can be laid virtually perfectly level from the footer until it daylights. The net result is that you are simply providing a resistance-free path for the water around your foundation to escape.

If you are unlucky, like me, you need to install a sump within your basement. The draintile pipe gets to thesump either through or under your footer. I always install a 6 inch pipe under the footer right where I knowI will install the sump. I actually install this pipe before the footer is poured. It's tough to tunnel!

An electrical pump pumps the water from the sump to either the outside of your house or into a storm water drainage system. Never allow the sump water discharge pipe to dump the water along side your foundation.This simply soaks the soil again!

Battery backup sump pumps are available to assist the regular pump in the event of primary pump failure or a storm related electrical outage.

Backfilling Basement Walls

Many a foundation crack is related to backfilling. Very few homeowners realize the risk of backfilling afoundation too quickly.

Don't forget that your foundation walls are simply beams or retaining walls. The walls act as a beam oncethe basement floor and the first floor subfloor are attached. Without these two elements, a foundation wallcan tilt inwards, crack, or even slide off the footer! Don't allow your builder to backfill until these floors arein place!

Also, did you know that it takes approximately 28 days (under ideal conditions!) for concrete to reach 75 percent of its design strength? I know of builders who backfill foundations within 4 days of being poured! Ihave seen huge cracks develop from foundations that were backfilled prematurely. Don't let it happen toyou!

Preventing Ponding

Model building codes mandate that the soil must fall away from a foundation. They actually state that theremust be 6 inches of fall within the first 10 feet of horizontal distance away from a house. If lot lines are tooclose for this to happen, then there must be some sort of drainage channel that allows gravity to pull water away from a foundation.



Furthermore, once this water is away from the foundation it needs to be directed to the lowest part of thelot. In other words, the lot grading plan needs to be completed so that water drains off the lot much like itdid before a house was built on the lot. It is a common sense issue. This can be easily accomplished if thehouse foundation sticks up out of the ground and backfill soil creates the needed slope.

If you have ponding problems now and it is too difficult to re-grade your yard you can drain these swampy

areas fairly easily. All you need to do is install a linear french drain system in the yard. This is a simpletrench system that contains perforated drain pipe and gravel. The trenches are just 6 inches wide and about18 to 24 inches deep. They follow the contour of your yard until they go past your house. Then the bottomof the primary trench levels out and before long the pipe will daylight!

Foundation Drain JM10

Location: 07 Thermal & Moisture

A 2D symbol for foundation perimeter drains and underslab drains in wall sections. InPerimeter mode, it draws the drain tile (pipe), gravel, cant strip, membrane, drainage board, and backfilled earth. In Slab mode, it draws the drain tile and gravel.

Dimensions (Perimeter version):

Height parameter: From the top of the footing to the top of the masonry ledge or grade

level, whichever is less. If there's no ledge, the height will go to the grade and no boardextension (see below) is needed. If there is a ledge, the height goes there and theextension streches to meet the grade.

Footing Width: Width of the footing beyond the wall, typically 6".

Cant Width: Width of the cant strip, typically 4".

http://www.onland.info/archives/2007/05/foundation_drain_jm10.php

http://www.onland.info/archives/2007/05/foundation_drain_jm10.php



Drain Diameter: Obvious

Drain Board Thickness: Obvious

Membrane Thickness: Needs to be enough to get the membrane/drain board edge clear

of the heavy contour line of the wall. This will depend on the scale and line weights, but5/16" seems to be a minimum. Be sure to check the printed output, not just the trueweight on the screen.

Board Extension: In the masonry ledge case, the height added to the top of the object tomeet grade level.

The grade line and backfill angles are controlled by the hotspot at the top right corner (left if mirrored).

The gravel depth matches the cant strip height, which is driven by the cant width.

The membrane overlap on the footing matches the radius of the drain.

The gutter is 2.5 times the drain diameter.

Dimensions (Slab version):

The gravel depth is defined by the drain diameter. The length is set by the Length

parameter.

There is also a Drain Only mode which draws only the drain. In this mode the Filter

atop the pipe can be on or off.

Attributes:

The Fill Pen is used for all the fills. The Outline Pen is used for the interior lines and thenon-cut edges. The Cut Pen is used for the edges along the wall. (This way, the wallcontour won't appear 'thinned' by the object.) The Grade Pen is used for the top lines.The grade line is usually one click heavier than the typical cut line weight.

The fills should be clear enough. But. In developing this object I realized that the proper fill for backfill earth had somehow slipped out of the templates. It's back now, but you

should make sure you have the fill when you use this object. Use Attribute Manager anddo the following:

• Go to the fills tab.

• In the right panel, click open and navigate to the 'NewHome10.tpl' in the zTemplatefolder.



• In the right panel, scroll down until you see fills number 102 and 103. Highlight both of them.

• Click 'Overwrite' (not 'Append') in the center, then Apply, and confirm themodification.

• Close up the Attribute Manager.

The fill you want is '*Earth Backfill'. BTW, undisturbed earth should use the fill '*Earth'.

Installing Drainage and Radiant Heating

A nice feature to add to your garage slab is a center drain for washing a car, boat etc.

Drainage pipes and radiant heat tubes should be placed and attached to the wire mesh before pouring your concrete slab. The slab should be pitched from the back towards thefront of your garage for proper drainage.

There are some features to your garage or workshop you will not be able to add after your foundation is complete, so decide up front during the planning phase which features likea drain or radiant heating you will include in the foundation.

Radiant heating is a nice, efficient heating system to use in a workshop or garage, sinceyou get heat without any need for blowers or air movement, which helps make for a moredust free environment. Also, the floor will be nice and warm for those occasions whenmechanical projects require you to sit, kneel or lie on the floor!



Adding a drain may also be worth considering. In some cases, a garage or workshopdrain simply uses drywell drainage; you just dig a hole and fill it with a course stone for water to drain into. Drainage pipe will be placed on the foundation bed and the drain placed before concrete is poured.

Alternatively, a connection to your sewage system may be required for your drainagesystem. Local codes are usually quite strict about what you can dump in garage drains. Afiltering system can also be installed to keep any contaminants from entering the soil or sewer system.

Sill Sealers and Concrete Sealers

You will also want to seal your garage or workshop to inhibit moisture, cold or hot air,and particles. There are two commonly used types of sealers; floor sealers and sill sealers.The sealers are normally applied during the construction to help keep your garage or workshop dry and well insulated.

Sill sealers use adhesive foam and the application will sit between the top of thefoundation and sill plate, creating a waterproof barrier.

A sill sealer will conform to the surface of your foundation to prevent any cracks or gapsthat could otherwise form between the foundation and sill plate as the concrete shrinks asit cures. Sill sealer applications have a strong adhesive on one side that will stick to your foundation. This does a great job of protecting against moisture, air, rodents, insects, etc.

Typically, concrete sealers are spray on applications designed to prevent moisture andvapor from rising up through concrete, which is porous. Concrete sealers can provide

other benefits as well, including preventing radon gas seepage and inhibiting the growthof mildew or molds. Concrete sealers can also help strengthen concrete and preventcracks over time.

You should always get advice from a professional when planning a foundation to be sureit is all engineered correctly for the intended structure it will support and to be sure itmeets all local building codes!



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

Foundation DrainageA sloped finish grade and properly placed perimeter drains will keep the basement dry

by Brent Anderson, P.E.

As a concrete contractor, I have a vested interest in how well the water on site iscontrolled. Underground water and runoff from rain and snow pose a threat both to thestructural integrity of the foundations I build and to below-grade interior living space.Wet basements and cracked foundations are difficult to fix after the fact, but good perimeter drainage, both at grade and down at the footings, is a cheap and easy way to prevent problems. If you follow these rules of thumb for perimeter grading and drain tile,you’ll sleep easy knowing that the water control systems you buried today won’t bubbleup into a callback tomorrow.

Surface Runoff

Although some wind-driven rain strikes the siding and drains onto the ground, most





surface runoff comes from the roof, and the amount of runoff varies according to the sizeand style of the roof. A gable roof deposits all runoff onto the ground under the eaves,with little runoff at the gable ends; a hip roof distributes the runoff more evenly on allsides (see Figure 1).

Gable Roof Runoff

Figure 1. Both of these roofscover approximately 2,500

square feet. The gable roof

deposits runoff along two sides of the house; the hip

roof spreads the runoff more

or less evenly along all sides. Main roof valleys and

dormers concentrate the

runoff into smaller areas on

the ground.

Hip roof Runoff

Roof Runoff

(from 2500 sq. ft. roof)

Rainfall Rainfall Volume Volume

Amount Rate (cubic ft.) (cubic ft.)

1 in. per hr. 200 1500

1 in. per day 200 15002 in. per hr. 400 30002 in. per day 400 300

Note: Every inch of rain, whether it falls during a one-hour downpour or an all-

day rain, deposits 1,500 gallons of water onto the ground around a typical

2,500-square-foot roof surface. During a winter rainstorm, every foot of melting

snow on the roof adds an additional 1,500 gallons.



In addition, valleys at main roof intersections and dormers can concentrate runoff into arelatively small area on the ground. In cold climates, runoff increases significantly duringspring rainstorms when higher temperatures and rain combine to melt snow on both theroof and the ground, adding to the total amount of surface water that must be drainedaway from the foundation.

Sloped grade.

Most basement water problems can be solved by properly sloping the ground around thehouse. The finish grade should slope away from the foundation at the rate of 1/2 to 1 inch per foot for 6 to 10 feet. A 2- to 4-inch cap of silty-clay material will keep runoff from percolating down through the backfill.

A sloped grade will not work for long, however, if the perimeter fill is not mechanicallycompacted, which is rare in residential construction. Instead, compaction is left to chanceand occurs slowly over a period of months or years, depending on climate and the type of

backfill used. Gravels and sands percolate faster and may reconsolidate more quickly — typically, from three months to a year. Silts and clays, which have a much slower percolation rate, may not compact for several years.

In either case, however, the result is a negative grade that directs runoff back toward thefoundation. Depending on the type of backfill, sooner or later the runoff will overwhelmthe footing drainage system, and basement water problems will appear. Silt or clay fill,which hold water longer than gravel or sand, can make the foundation more susceptibleto cracking from frost action; hydrostatic pressure may also develop with these types of fill, forcing water through the slab-footing joint. Rarely will any of these problems appear immediately, but down the road, you’ll be faced with a messy and expensive repair job.

Gutters. While gutters can dramatically reduce the total ground area onto which roof water drains, it is crucial to use a sloped leader to extend downspouts along the ground tocarry water away from the foundation (Figure 2).

Downspout with SlopedLeader

Figure 2. Sloped

downspout leaders

should discharge at least 10 feet away



from the foundationwall.

Downspout with Catch Basin

Use solid drain pipe

to carry runoff from

a concrete catch

basin to daylight or a drywell .

Otherwise, a gutter-and-downspout system compounds the drainage problem byconcentrating the entire roof runoff load into a few small areas, usually at the housecorners. Leaders should discharge onto sloping ground at least 10 feet from thefoundation. If downspouts dump directly into a catch basin on the surface or underground, the collected runoff should be carried through a solid drain pipe to adrywell or to daylight.

Keep gutters clear of leaves, pine needles, and ice. Overflow from blocked gutters canfollow the contour of the gutter and saturate the soffit and siding, often making its way



into the wall and wetting the insulation, drywall, and floor. Similarly, gutters in coldclimates can encourage ice damming, with the same damaging results.

Hardscape.

Concrete or paver block sidewalks can also control percolation of runoff into the backfill(Figure 3) — I’ve measured reductions in runoff percolation of between 300% and 500%.

Concrete or Paver Sidewalk

Figure 3. A properly

sloped concrete or

paver sidewalk will reduce the amount of

runoff that

percolates throughthe backfill (top).

Where perimeter

plantings are used tolandscape, improve

drainage by burying

a sheet of

polyethylene below

the plant bed, withopenings cut out for

roots (bottom). Tie shallow perforated

drain tile to solid

pipe to carry water to daylight or a

drywell.

Plant Bed with Drain

Again, the hardscape should be wide enough to cover the entire backfilled area, and thesurface should slope away from the foundation walls.



A less expensive technique is to bury a sheet of polyethylene in a plant bed. The polyshould cover the backfilled foundation trench and slope to a perforated drain tile laid parallel to the foundation. Use solid pipe to carry runoff to daylight or to a drywell. Inlandscaped areas, cut openings in the poly to accommodate plant and tree roots.

Buried poly works well, so long as the backfill has been compacted. With a negativegrade, however, the poly actually directs the water into the foundation wall. Plant andtree roots near the foundation can also compound problems with uncompacted fill, because their root systems absorb water and cause the soil to reconsolidate quickly. In adrought, tree roots can pull so much moisture out of the soil that the foundation maysettle.

Perimeter Footing Drains

Foundation perimeter drains work in both directions. They not only carry rainwater percolating down through the backfill away from the foundation, they also relieveexcessive hydrostatic pressure from rising groundwater. By helping the backfill dry out

more quickly, properly installed perimeter drains reduce lateral soil pressure, which inturn means that foundation walls can be designed to use more porous materials and lesssteel.

There’s a right way and a wrong way to install perimeter drainage. Unfortunately, manyfoundation contractors and home builders labor under a false sense of security, reasoningthat if complaints about leaky basements don’t surface within the first year or two after a project is completed, their construction techniques must be working. The fact of thematter is that basement water problems that occur within the first twelve months areusually related to waterproofing defects. Drain tile problems typically take many years todevelop. Thus, many contractors have buried time bombs that will eventually blow up in

their faces.

Holes Down

Although porous cement-based tile is still in use today, most residential contractorswould agree that perforated 4-inch-diameter plastic pipe produces tighter joints and iseasier to work with. Not all would agree, however, on which direction to place the holesin the pipe when installing footing drains.

The answer depends on the type of pipe. Flexible HDPE (high-density polyethylene) isslotted all the way around, and some rigid PVC has a pattern of holes around the entirecircumference. With these types of drain tile, there is no “right” direction because thereare openings on all sides. Plugged holes on the bottom are cleared by water enteringthrough the sides and top.

The most popular drain tile, however, is rigid PVC that has just two parallel rows of holesclose together along its length. The classic approach is to lay this type of drain tile withthe holes facing down, in the five-o’clock and seven-o’clock positions. This allows arising water table to enter the pipe at its lowest point.



Filter fabric. While hydrostatic pressure helps to flush silt from the pipe, all buried draintile should be surrounded with coarse gravel or crushed stone, and wrapped with afiltering material. Without a filter, silt will contaminate the stone and eventually enter and plug the holes in the pipe (Figure 4).

Figure 4. Without a filter to keep silt from contaminating the surrounding stone, drain

tile can be rendered useless within just a few seasons (left). Pipe that is pre-wrapped or

“socked” with filter material will prevent drain tile from becoming plugged (above).

Various geotextiles are available in rolls, and pre-wrapped or “socked” pipe — pipe thatis manufactured with a filter sleeve already in place — is also available.

Drain Tile Location

Filter paper and properly oriented perforations, however, will not guarantee that drain tilewill work. The pipe must also be installed carefully and in the right location with respectto the footing and any interior slab.

From a pure engineering point of view, the ideal place to lay exterior drain tile isalongside the footing, because water from a rising water table enters the pipe sooner (Figure 5).

Pipe Even with Top of

Footing

Figure 5. The best location for

rigid drain tile is alongside the

footing. Minimum requirements

for stone cover depend on



whether the tile is flush with the

top of the footing (top) or the

bottom (middle). In either case,

the top of the interior slab should be at least 6 inches above the top

of the drain tile. The pipe can be

laid level or pitched slightly.Where drain tile must be

located lower than the bottom of

the footing (bottom), avoid undermining the footing by

keeping the pipe outside of a 60-

degree angle measured from the

corner of the footing. Thislocation also requires more stone

cover for the pipe.

Pipe at Bottom of Footing

Pipe Below Footing

The drain tile does not need to be sloped, although a slight pitch helps keep the pipe clear of silt and clay (particularly when the pipe has just two rows of holes on the bottom).Avoid trying to slope flexible drain tile, however, because you can inadvertently createdips and sags that will eventually collect silt and clog the pipe (Figure 6).



Figure 6. Regardless of the type of pipe used or its shape, unfiltered drain tile can easily

be plugged with silt and clay (left). Water-seeking roots from trees growing too near the foundation can also completely clog perimeter drains (right).

In fact, undulating drain tile can result in premature failure of the drainage system. This problem is more pronounced when trees are growing close to the foundation, because wetsilt and clay accumulating in low spots become targets for water-seeking tree roots in dry periods or in dry climates. In a relatively short period of time, tree roots can completely

plug drain tile.

Some contractors create an even lower elevation for the tile by digging a small trenchnext to the footing. To avoid undermining the foundation, however, most codes requirethat the tile be placed outside a 60-degree angle from the footing.

Drain tile can also be placed on top of the footing. The advantage here is that the tile will be as level as the footing — a good strategy when using flexible pipe (Figure 7).

Figure 7. To keep flexible drain tile from developing low spots that will collect silt, place

it on top of the footings, making sure that the top of the pipe is not higher than the top of the interior slab.

But this higher placement doesn’t control a rising ground water table as effectively, andmay require raising the elevation of the interior slab.

Specialty drainage products.



Today there are several products on the market, such as Form-A-Drain (CertainTeedCorp., P.O. Box 860, Valley Forge, PA 19482; 800/233-8990; www.certainteed.com),that provide both the footing form and the drain tile (Figure 8).

Figure 8. Form-A-Drain stay-in-place footing forms ensure a level perimeter drain and have a larger capacity than pipe systems (left). To control hydrostatic pressure, dimpled

drainage panels fastened against the foundation wall carry water from the backfill into

the perimeter drains (right).

These systems not only ensure that the drainage system is level, they often provide moreflow capacity than traditional pipe systems.

On sites where an exceptionally high ground water table creates intermittent hydrostatic pressure on the foundation walls, dimpled sheets can be used in conjunction withstandard drain tile. These membrane systems provide a waterproof barrier while also

directing excess ground water from higher up on the foundation walls into the perimeter drains.

Discharging Collected Water

Capturing ground water in a perimeter drainage system is only half the battle — onceyou’ve collected water in the drain tile, you have to dispose of it somewhere. Dischargingwater into sanitary sewer systems is generally illegal, which leaves two basic ways to getrid of the water: On sloped sites, you can extend unperforated drain tile to daylight anddischarge the water on the ground; on flat sites, you can collect the water in a sump basket and pump it to a discharge area away from the basement.

Gravity discharge. Two elements are critical to proper function of a gravity drainagesystem. First, although the perforated drain tile around the foundation itself may be level,solid pipe running from the foundation to daylight should slope at the rate of 1/16- to 1/8-inch per foot. Second, the open end of the discharge line should prevent entry by rodents,frogs, snakes, and reptiles. One method is to cover the exposed end of the pipe with 1/4-inch hardware cloth. Alternatively, you can bury the end of the pipe in crushed stone,which will allow the water to seep out below grade.



Pumped discharge. While gravity discharge to daylight is cheap and easy, I recommendinstalling a sump basket as a backup. A submersible sump in the bottom of the sump basket connects to a hose or rigid pipe system that carries the collected water out of the basement. If you provide for the collection sump at the time the foundation and slab are placed, the pump and discharge piping can be installed later if needed.

The sump basket should be located inside the foundation, where it can pick up groundwater that rises under the slab. On a flat site where all ground water must be pumpedaway, water from perimeter drains should also be directed into the sump through drainagesleeves in the footing (Figures 9a & 9b).

Figure 9a. An interior sump basket picks up excess

water flowing through sleeves in the footing.

Figure 9b. A submersible pump connected to a hose or rigid pipe discharges the water on the ground away from the foundation.

To avoid having to excavate later, be sure to place sleeves before the footings are poured.Use 4-inch-diameter pipe, and space sleeves 6 to 8 feet apart around the entire perimeter of the footing. In special cases where the slab is placed a foot or more above the top of



the footings, you can locate sleeves in the foundation wall. Although water passingthrough the sleeves or under the footing will generally find the sump basket on its own, Irecommend an interior drain pipe at the perimeter, terminating in the sump basket.

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• From: Residential Concrete July-August 2007• Posted on: July 23, 2007

10 Tips for Foundation Drainage

It is much easier to do foundation drainage right in the first placethan to repair it later.

By:William Palmer Jr.

Keeping water drained away from home foundations is important for three reasons. First,if there is living space on the other side, the owner will want it to stay dry. Good drainageis the first step toward accomplishing that, then waterproofing. Second, soils supporting afoundation need to stay at a consistent moisture level to prevent settlement, heave, or

differential movement. Last, but not least, drains are required by the building code. Hereare a few things to keep in mind:

• Code requirements: The International Residential Code (IRC), in SectionR405.1, requires drains “around all concrete or masonry foundations that retainearth and enclose habitable or usable spaces below grade.” The IRC goes on to provide details about what kind of drains are sufficient. However, very well-drained soils are an exception and mixtures such as sand and gravel do not requiredrainage.

• Moisture: There are two zones of subsurface moisture: the aeration zone (where both water and air exist) and the saturation zone. Generally, the saturation zone is

everything below the water table, which is the level at which water rises to in awell. The saturation zone is seldom an issue in residential construction—soilmoisture is the concern.

• Loss of soil moisture: Soil moisture beneath a foundation is lost in a triangular configuration, so the deepest dry area is just outside the edge of the foundationand the ground beneath the middle of the slab remains saturated. Differentialdrying or differential amounts of moisture in the soil can create problems,especially in expansive soils, which in many parts of the country are more the rulethan the exception. In some areas, homeowners actually have to water their foundations to maintain soil moisture.

• Surface drainage: Controlling surface water is critical to controlling soil

moisture beneath the foundation. The ground surface should slope away from thehouse at between ½ and 1 inch per foot for at least 6 feet—10 feet is better. Becareful of poorly compacted backfill, though, because that will soon mean that thesurface will slope back toward the house.

• Gutters: Downspouts should discharge on sloping surfaces at least 10 feet fromthe foundation. Where that isn't possible, downspouts should discharge intodrained catch basins.

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• Trees: According to the U.S. Department of Housing and Urban Development,trees should be planted no closer to the foundation than their eventual height. This prevents tree roots from filling perimeter drains and inhibits the tree from suckingall the water from the soil, which could lead to settlement.

• Subsurface drainage: Perimeter drains should be made from rigid drain tile or

perforated pipe. Although flexible corrugated plastic pipe can be used, care must be taken to prevent it from being crushed during backfilling. One simple methodis to use Form-A-Drain, which is a combined footing side form and drain pipe.

• Drain pipes: Drain pipes should be positioned alongside the footing—the bestspot is near its base. Although tile doesn't need to be sloping, low spots (whichcan fill with silt) must be avoided. With flexible tile, a good location is on top of the footing, which helps keep them from developing low spots. For an excellentarticle on perimeter drains, go to www.jlconline.com and search for foundationdrains to find the article Foundation Drainage by Brent Anderson—it will cost$2.95.

• Drainage boards: In wetter areas, drainage boards installed on a concrete

foundation wall will allow water to drain quickly to the perimeter drain and will prevent any buildup of hydrostatic pressure next to the wall. Several systems areavailable, including Delta-MS from Cosella Dorken and Platon from Armtec.

• Finally, remember that it is much easier to do foundation drainage right in the first place than to repair it later.

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