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Old 09-01-2010, 09:15 PM   #1
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A breach in the footings = water?


Our 30 year old rancher sits on a level but graded lot.

Over the past couple seasons we have noticed that the 3’ crawlspace seems damper and mustier than in past years.

On the CS wall closest to the street there lies the perimeter drains along with a lateral drain to the street storm drains.

Out of general concern we had a perimeter drainage company come in and check the drains for integrity using their remote camera. They couldn’t confirm any blockages but strongly suggested we dig up the entire perimeter drains nonetheless and re-align them so their slopes would definitely be back to current codes. They intimated that the drains could very well have become backgraded or sagging through settling, etc. If we did this it would mean a complete drainage overhaul up to municipal specs. Cost : 40+k !

Upon further investigation I found that the original contractor had installed a 4" crawlspace drain with p-trap into the front perimeter drains. It was done after the foundation was poured. It looks like they had busted out the footing along with a portion of the interior parged concrete floor in order to get the clearance for the drain and its p-trap).



notice street lateral coming off at 45 deg angle

(Inside CS) As the photo below indicates, it does now appear that the grading of perimeter drains may have been affected by the adaptation of the crawlspace drain to the outside perimeter drains through a T-connection. The water level seems to be at the same elevation as the perimeter drains. Perhaps the main run has sagged at that point in the wall?


 
Note: the 1" poly pipe through the wall, above the crawlspace drain, is for hot water heater overflow to a makeshift outside pit. This was the original purpose for the excavation in the first set of photos -- I thought the cs drain was plugged a few years back. As it turned out it was more than than, huh.

After determining that the installation included a p-trap under the footing and thus creating a sort of water pit, it does seem obvious that this has been a major cause of our moisture -- when it rains hard, the excess water drops to the perimeter drains pipe as it should but also into the pit that was formed by the crawlspace drain and its p-trap. When the pit overflows (up to the level of the perimeter drains), it seeps under the parged concrete floor and rises (through capillary) around some of the center support piers, etc.).

I figure if we can mitigate at least this waterhole problem then much of our moisture and dampness may be eliminated.

So, how to go about remediating the crawlspace drain/p-trap pit affair?
What I have thought to do is, first compacting new concrete into the hole and thus patching the hole in the footing. This would also restore the original barrier down to hardpan.

But the p-trap assembly that goes into the outside perimeter drain T-fitting is only dry-fitted – it wasn’t glued in place! Is this loose fit normal for a connection to perimeter drains? Shall I ignore this as an oversight and just encase the p-trap in concrete?

After the foundation footing void has been sealed up, we thought we’d see how the water level is then, and if still poor we could dig the pit even larger (ahead of the footing and into the broken floor) and install a small sump pit and pump. Does that make sense?
 







More information on the foundation perimeter drains: the drains are located just below the foundation footing tops but not at their base. They are in a bed of drain rock, which is on clay and hardpan (below the footings as normal).

Appreciate your comments.

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Old 09-01-2010, 10:23 PM   #2
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A breach in the footings = water?


Is your crawl space well vented to the outside during warmer months?

It is okay for additional ground water drain pipes to feed into the perimeter drain system, but gutter water and washing machine water should not be poured in.

If rain water or gutter water pools up against the foundation, that must be fixed as part of your overall project.

A perimeter drain system is not meant to absorb water. The system must ultimately take the water to the ground surface some distance away and downhill, to a city storm drain system, or to a pit with a sump pump.

A perimeter drain system is intended to collect water by gravity before the water can seep up into a basement or crawl space but is not intended to reduce the humidity of a crawl space.

Yes a big breach in the footing will let water in. But it is hard to seal the foundation completely and a properly working perimeter drain system will keep water out even if there are tiny cracks in the footing or foundation.

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Last edited by AllanJ; 09-02-2010 at 08:17 AM.
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Old 09-02-2010, 11:02 AM   #3
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A breach in the footings = water?


Thanks much for taking the time to look at my problem

Quote:
Originally Posted by AllanJ View Post
Is your crawl space well vented to the outside during warmer months?

Yes it is. But I have recently decided to close all vents and look at providing a mechanical exhaust in order to regulate moisture from the outside (dew point).
We also intend to drape the foundation walls in poly and seal it to the parged concrete floor. To reinsulate the subfloors above, we are thinking of yanking down the inadequate R14 fg insulation and installing radiant barrier material just under the joists. But all this has been put on hold until this water problem has been satisfied.

It is okay for additional ground water drain pipes to feed into the perimeter drain system, but gutter water and washing machine water should not be poured in.


If rain water or gutter water pools up against the foundation, that must be fixed as part of your overall project.

A perimeter drain system is not meant to absorb water. The system must ultimately take the water to the ground surface some distance away and downhill, to a city storm drain system, or to a pit with a sump pump.

A perimeter drain system is intended to collect water by gravity before the water can seep up into a basement or crawl space but is not intended to reduce the humidity of a crawl space.


Our system is 30 years old and as such it is a single layer perimeter drain around the house. All 8, except for 2 end-of-run downpipes, pour into the drains -- those 2 are turned 4' out into the sloping yard.
I'm unable to turn the other downpipes out as the rest of them are over concrete driveway or walkways. Washing machine water (gray water) goes into the sewer system.


Yes a big breach in the footing will let water in. But it is hard to seal the foundation completely and a properly working perimeter drain system will keep water out even if there are tiny cracks in the footing or foundation.

Aside from the pool of water that collects at the base of the broken footing, most of the crawl space seems dry ..well, with the exception of some dankness. And after temporarily placing poly sheeting over the pool, we've noticed the odor dissipating. So far, no apparent molds or wetness on the floor joists above, no hanging batt insulation full of moisture.

Not knowing for sure that the drains are sagging or out of grade, I would hate to dig up the front perimeter drains just to check and adjust them, as brand new landscaping has just gone in -- hmm, perhaps having micro sprayers close to the foundation and spraying out might be contributing to the saturation of soil?? There are several other junctions along this stretch of perimeter drain. To dig the line up would probably involve digging some of the other connections including the lateral in order to properly grade the area ..yes, totally wrecking our new garden.



..in the photo above, the CS drain is just north of the lateral "Y". The white pipe joining the drains is an auxilliary one that was put into a large remote pit when we did the sewer connection a while back. The pit was dug only as a precaution in case the lateral ceased to work (another story ).

Yes, the footing breach does concern me, especially with such a void dug under it (for the big 4" p-trap). I can definitely understand how water can collect into that lowest point -- the pit.

So aside from redoing the entire perimeter drains, as a second option what would be the best way to remedy this from the inside ..fill this up with concrete/hydraulic cement ?
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Old 09-02-2010, 11:57 AM   #4
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A breach in the footings = water?


Don't do anything yet. Leave the excavation open for awhile but get some gravel and pile that up around it so ground water and mud doesn't pour right in. Observe the water level in the excavation during and after a heavy or prolonged rainy period.

Is that blue pipe perforated? The perimeter drain is working acceptably if no more than half of it gets submerged during or after a heavy or prolonged rain.

It is better to let the gutter water pour over the driveway instead of fill the perimeter drain to the brim. If the perimeter drain fills up then you will get water in the crawl space.

You can have two drainage systems, one with non-perforated pipes and sealed joints to get rid of gutter water and the other with perforated pipes to keep ground water from coming up into the crawl space or basement. The non-perforated system must drain water far enough away and downhill so the water cannot get into the perforated system or make its way back to the foundation.
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Last edited by AllanJ; 09-02-2010 at 12:09 PM.
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Old 09-02-2010, 02:08 PM   #5
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A breach in the footings = water?


Further to your comments..

Quote:
Originally Posted by AllanJ View Post
Don't do anything yet. Leave the excavation open for awhile but get some gravel and pile that up around it so ground water and mud doesn't pour right in. Observe the water level in the excavation during and after a heavy or prolonged rainy period.

Before I dug out the p-trap, the hole was already filled with gravel to the level of the CS parged floor (there is a 1.5' semi-circle breakout in the floor to the footing). When it rained heavily, the top of that gravel was wet. This clue was one that led me to excavating the area and I discovered the pit -- and subsequent water pond -- underneath.

Is that blue pipe perforated? The perimeter drain is working acceptably if no more than half of it gets submerged during or after a heavy or prolonged rain.

Yes, the pipe is perforated. Hmm, hadn't thought about the fact that the pipe could be that full of water. But then we have a huge roof surface with over 200 linear feet of gutters. So I guess 4" of perimeter pipe would see its capacity filled pretty fast, huh Other than visual overflow signs, how can one tell just how full these pipes get?

It is better to let the gutter water pour over the driveway instead of fill the perimeter drain to the brim. If the perimeter drain fills up then you will get water in the crawl space.

Agreed. But I just can't allow the downspouts blocking foot traffic, either on the driveway or walkways. Since turning out the 2 downspouts at the end of the house has definitely helped the water level in the CS over the past few years. The other downspouts could be a problem to turn out (see photo below)



I've read someplace that there are attachments for the bottoms of downpipes that unwrap to spill water then recoil when dry (like those New Years Eve blow-whistles)??

You can have two drainage systems, one with non-perforated pipes and sealed joints to get rid of gutter water and the other with perforated pipes to keep ground water from coming up into the crawl space or basement. The non-perforated system must drain water far enough away and downhill so the water cannot get into the perforated system or make its way back to the foundation.

Well, that would entail redoing my entire perimeter drain system and bringing it up to today's code. I cannot affort that cost.

Taking your comments into consideration, it would seem that I need to find some other way of losing gutter water ..either by boosting the integrity of the drains, finding a way to redistribute the downpipe flows, or add a sump in the CS and pump that effluent outside and away from the house. Hmm... $40k vs $400. I must be on track somewhere here




note: the area of discussion is along the wall where the ferns are planted.
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Old 09-02-2010, 04:02 PM   #6
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A breach in the footings = water?


A new perimeter drain system may not be added to an existing house at a level below the footings. Otherwise the footings and foundation will shift and heave when you excavate below them.

Water accumulating below the perforated perimeter drain pipes will never be captured by the pipes. But the perimeter drain pipes should keep this level several inches below basement floor level provided the drain pipes don't fill up completely.

Your water pit was probably formed by redistribution of dirt after numerous wet dry cycles. If not suitable for becoming the sump pump pit, this pit may be filled in if you wish. I suggest coarse sand or fine gravel.

To prevent mold and mildew, keep the crawl space well ventilated with large openings until you install fans. Dew is less likely to form when there is good circulation.
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Old 09-02-2010, 04:16 PM   #7
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A breach in the footings = water?


.....

Quote:
Originally Posted by AllanJ View Post
A new perimeter drain system may not be added to an existing house at a level below the footings. Otherwise the footings and foundation will shift and heave when you excavate below them.

Water accumulating below the perforated perimeter drain pipes will never be captured by the pipes. But the perimeter drain pipes should keep this level several inches below basement floor level provided the drain pipes don't fill up completely.

Your water pit was probably formed by redistribution of dirt after numerous wet dry cycles.

If not suitable for becoming the sump pump pit, this pit may be filled in if you wish. I suggest coarse sand or fine gravel.

Will this just make the area a swamp instead of a pond? Wouldn't concrete or hydraulic cement be a better barrier (as a substitute for the lost hardpan soil) ie, re-extending the broken footing down to the existing hardpan ?

To prevent mold and mildew, keep the crawl space well ventilated with large openings until you install fans. Dew is less likely to form when there is good circulation.

To move the air, I currently have a modified 42" ceiling fan attached to the joists. Can you suggest a good exhaust fan option (2000 sq ft) to pull air out through one of the old vents ?
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Old 09-02-2010, 09:22 PM   #8
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A breach in the footings = water?


Quote:
Will this just make the area a swamp ...
All the while the pit has standing water in it, the ground for miles around, er, probably at least 30 feet in every direction, below that level is saturated with water. That level where the soaked ground meets not so wet soil closer to the surface is called the water table. During prolonged dry weather the water soaks further into the ground and the level in that pit together with the water table goes down. Only when the water table drops far enough will the pit become empty. (In reality the water table can vary a little even over distances of just a few feet when the soil from one place to another varies in consistency/porosity.)
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Old 09-02-2010, 09:30 PM   #9
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A breach in the footings = water?


Quote:

Yes, the pipe is perforated. Hmm, hadn't thought about the fact that the pipe could be that full of water. But then we have a huge roof surface with over 200 linear feet of gutters. So I guess 4" of perimeter pipe would see its capacity filled pretty fast, huh Other than visual overflow signs, how can one tell just how full these pipes get?
Quote:
Taking your comments into consideration, it would seem that I need to find some other way of losing gutter water ..either by boosting the integrity of the drains, finding a way to redistribute the downpipe flows, or add a sump in the CS and pump that effluent outside and away from the house. Hmm... $40k vs $400. I must be on track somewhere here
Just a quick thought. Why not utilize a rain barrel to recycle some of the rain water from the gutters to water your new landscaping?
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Old 09-06-2010, 10:48 AM   #10
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A breach in the footings = water?


Thanks for your comments ..it's given me much to think about

From outside the house I've decided to do a re-dig of the drain spur (that goes into the crawl space). I'll probably make the p-trap more permanent (instead of dry fit that is current) so I can run the hotwater tank overflow into it ..instead of the 1" poly that currently runs outside through the broken footing.

After clearing the rock under the perimeter drain, I'd like to recast the void in the broken footing, then water seal that section of wall. After that's complete it will be covered with landscape fabric and backfilled with drain rock as original.

Question: any suggestions of the best way to recast that footing -- so it's vertical inside and out?

Also, further down the perimeter drains, I plan to redig the lateral (to the street) and try to flush it using a length of 1/2" irrigation poly attached to the end of a garden hose. Hopefully it can go all the way to the street storm drain tie-in. Afterwards, a wye will be installed in the lateral for later cleanout.

As for the rain barrel idea. I had though about that years ago. But we already have access to plenty of water and the hassle and expense of putting in special barrels wouldn't be worth it for the little water our huge garden requires -- thanks for the thought though.
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Old 09-07-2010, 01:37 PM   #11
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A breach in the footings = water?


As Allan suggested, the dampness in your crawl space may have nothing to do with improper drainage.

Moisture problems in the crawl space are fairly common, and come as a result of two main factors:

- Ground moisture evaporating into the crawl space
- Crawl space vents

For a long time, crawl space vents were thought to help dry out crawlspaces. However, due to differences in temperature between the crawl space and the outside, several studies conducted by reputable independent organizations such as Advanced Energy, Habitat for Humanity and Building Science Corp., concluded that crawl space vents actually contribute to make crawl spaces wet and moldy.

In other words, crawl space vents are a scientific fallacy. The picture below illustrates what happens in your crawl space on a nice summer day:



To solve this problem, Advanced Energy, Building Science Corp and the U.S. Department of Energy recommend a process called encapsulation.

That means completely isolating the crawl space from ground and outside air, by lining the whole space with a sturdy vapor barrier, sealing it air tight and then running a dehumidifier or a crawl space conditioning system to keep it dry.

This process is reported to make homes an average of 18% more energy efficient as well by cutting energy losses, which can be as high as 50% if you have air ducts running in the crawl space.

I'd strongly suggest you look into it, and the Advanced Energy website on crawls paces (www.crawlspaces.org) is a great place to start. Start by looking at their videos.
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Old 09-07-2010, 02:21 PM   #12
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A breach in the footings = water?


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As Allan suggested, the dampness in your crawl space may have nothing to do with improper drainage.

Moisture problems in the crawl space are fairly common, and come as a result of two main factors:

- Ground moisture evaporating into the crawl space
- Crawl space vents

For a long time, crawl space vents were thought to help dry out crawlspaces. However, due to differences in temperature between the crawl space and the outside, several studies conducted by reputable independent organizations such as Advanced Energy, Habitat for Humanity and Building Science Corp., concluded that crawl space vents actually contribute to make crawl spaces wet and moldy.

In other words, crawl space vents are a scientific fallacy. The picture below illustrates what happens in your crawl space on a nice summer day:



To solve this problem, Advanced Energy, Building Science Corp and the U.S. Department of Energy recommend a process called encapsulation.

That means completely isolating the crawl space from ground and outside air, by lining the whole space with a sturdy vapor barrier, sealing it air tight and then running a dehumidifier or a crawl space conditioning system to keep it dry.

This process is reported to make homes an average of 18% more energy efficient as well by cutting energy losses, which can be as high as 50% if you have air ducts running in the crawl space.

I'd strongly suggest you look into it, and the Advanced Energy website on crawls paces (www.crawlspaces.org) is a great place to start. Start by looking at their videos.
I have checked out the sites mentioned, and have now sealed the crawlspace vents. I've also covered the water pool (inside at the footing) with a sheet of poly (until I redig and repour the broken footing from the outside). The CS is now noticeably drier and doesn't have near the dank smell it did even last week! I do have a old ceiling fan mounted to the bottom of the joists and that seems to move the air around at least.

I may eventually drape poly down the concrete walls onto the parged floor, but want to do this in stages as I'd like to monitor the progress.

In the meantime and after fixing the footing, I plan to rent a dehumidifier and dry the air out as much as possible so as to establish a better baseline for monitoring.

I am thinking of placing one of those Tjernlund crawlspace fans http://www.tjernlund.com/crawl_Space_ventilation.htm devices at one of the vents (reopening it) and have it exhaust the crawlspace via an opposing vent (scaled to makeup-air dimensions).
My question though now becomes, wouldn't this mechanical fan just draw in even more moist outside air and bring things back to square one ie: make things worse?
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Old 09-08-2010, 09:33 AM   #13
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A breach in the footings = water?


In our experience, yes.

If the supply air is coming from the outside, you will most likely make things worse because the temperature differences will still cause the RH on the outside air to rise as it enters the crawl space.

Instead, consider using a self emptying crawl space dehumidifier on a regular basis or using a crawl space conditioner which is basically a fan that draws conditioned air from the upper floors instead.

Whatever you do, don;t open the vents. Keep these crawl space vents sealed and, until you get around to completely encapsulate it, (which is the only way to control the moisture completely) keep a vapor barrier on the ground to keep some of the ground moisture from evaporating into the space.
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Old 09-08-2010, 12:16 PM   #14
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In our experience, yes.

If the supply air is coming from the outside, you will most likely make things worse because the temperature differences will still cause the RH on the outside air to rise as it enters the crawl space.

Instead, consider using a self emptying crawl space dehumidifier on a regular basis or using a crawl space conditioner which is basically a fan that draws conditioned air from the upper floors instead.

Whatever you do, don;t open the vents. Keep these crawl space vents sealed and, until you get around to completely encapsulate it, (which is the only way to control the moisture completely) keep a vapor barrier on the ground to keep some of the ground moisture from evaporating into the space.
I guess that's the dilema, huh. Two schools of thought : vent vs no-vent.

When I queried Tjernlund, the folks that make the crawl space vent, their analogy was "We like to use the analogy of a stagnant pond vs a pond with a stream running through it. Both ponds might have the same amount of water in them but the pond with the stream running through it (i.e. ventilation) is generally a healthier pond."

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Old 09-08-2010, 01:02 PM   #15
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Hi Daler,

In my opinion, it really is past the "two schools of thought" phase on this matter.

Encapsulation is recommended by the U.S. Department of Energy and the U.S. Green Building Council.

Plus, encapsulation doesn't mean not providing any type of air to keep the crawl space dry.

The thousands of studies only show that this air should not come from the outside because of the mentioned problems.

What encapsulations does is: it includes the crawl space into the internal envelope of the building so that it benefits from the conditioned indoor air, which is everything but stagnant.

It also curbs energy loss through the crawl space making your whole house easier to cool and heat.

Due to the way the air moves in buildings, air is constantly being sucked from the lowest levels to the upper levels of the house. It is called the "stack effect".

So just by opening the vents and allowing that humid air into the crawl space, you are allowing it to enter the upstairs floors as well and you are also making both your a/c and heat work harder. You are paying to cool and heat all that air. Which is why crawl space encapsulation also makes homes and average of 18% more energy efficient.

If you research a bit more you will see that today's green building and green retrofitting practices all call for tightly sealed building envelopes, so opening up a huge gap in the envelope with vents makes very little sense.

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