# Gravel against foundation to stop water



## mnp13 (Jan 16, 2007)

*Gravel against foundation to stop water??*

Ok, first of all, the house I am writing about is not mine, and I don't have anything to do with the repair being done or the decisions that were made with the repair. However, I'm having trouble wrapping my brain around what was done, so I'm hoping someone can clear it up for me.

First - the situation. Mid-70's construction, cinder block finished basement with floating slab floor. Basement is chronically damp, and the walls and insulation were torn out to reveal a crack in the foundation wall. When there was heavy rain, the water was actually visibly running down the wall. The soil is very high clay content, and when they were digging out the drain pipe (the gutters drain into a buried pipe system) they found that the underground pipe was disconnected (that was fixed.) So, since the foundation wall was exposed, they patched the crack from the outside.

Here's where I get confused:
Instead of putting the dirt back, they filled the hole with gravel, then topped it with dirt. _As it was explained to me_, the heavy clay soil doesn't drain very well, so it's putting pressure on the foundation. When the water in the soil freezes, it puts a lot of pressure on the wall and will make it crack more. The gravel will stop that from happening because it won't hold any water.

However, _as I understand it_, they basically just made a dry well up against the basement wall. The gravel will be a low point, easy for water to run to, and will actually create a large "pool" of water up against the wall. 

Yes, the downspout issue was fixed, so there should be less water to begin with. The soil on top was also correctly graded - both of those issues should put less water in the vicinity of the foundation. 

The next project for the house is to dig up the dirt along the rest of the foundation wall (they only did one small section) and put more gravel in it. No, this is not a french drain, with a pipe in the base of it. It's just gravel back fill against the foundation wall.

I'm not saying this was a "good" or "bad" course of action to have taken. I just don't understand it, and any work on a house is a learning tool for me so I'm hoping someone can explain it to me a little better than above.

Thanks,

Michelle


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## jklingel (Dec 21, 2008)

I'm confused, too. Gravel is usually a medium to let water get down to a drain, which goes to daylight or a sump. If the water is just going to sit there as you describe, then... call me Confused in Fairbanks. Perhaps they are figuring on water being very minimal now that the upper issues were addressed. Wish I could help more.


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## joed (Mar 13, 2005)

The key to the system is the drain tile around the bottom of the foundation. The gravel is fine as long as the weeping tile has somewhere to drain the water.


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## jklingel (Dec 21, 2008)

Joe: The problem is, if I read correctly, this job does not have any tile at the bottom; just a pit filled w/ gravel.


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## 4just1don (Jun 13, 2008)

I have same issue and same question sorta. Backfilled whole new basement with gravel for reasons stated in this thread BUT I do have weep tile tied to inside sump pump.

About 2 foot plus or minus from house. Now how do I keep the water out of the top from running down?? thought of plastic on good grade with dirt on it,,,then a bark cover since 4 or 6 inches of dirt wont grow anything with plastic under it...is this the BEST cap??? or pour concrete 2 ' around whole house????


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## joed (Mar 13, 2005)

Never heard of a foundation without drainage tiles at the bottom. I would say you have a problem. It is going to fill with water and where is the water going to go? Through the wall most likely.


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## Willie T (Jan 29, 2009)

Here is a right way and a wrong way. Notice that the gravel is kind of useless without that bottom drain pipe?


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## Daniel Holzman (Mar 10, 2009)

The confusion here is the purpose of the gravel. Clearly it would be better if the gravel were part of a perimeter drainage system, but it is not. Perhaps the homeowner could not afford to install a drainage system, or they did not feel it was necessary, for whatever reason this gravel is NOT PART of a drainage system.

The explanation that gravel exerts less pressure against the wall than clay is essentially correct. Theoretical analysis of backfill pressure shows that granular, free draining fill such as clean gravel, crushed stone, or clean sand, will exert lower pressure against the wall than materials such as silt, clay, or other fine grained material. Additionally, it is correct that clean gravel will not exhibit frost heave, even if the gravel is saturated, because the water in the gravel can migrate freely as it freezes. The water in the gravel may freeze, but the water will not exert significant pressure against the foundation, because the ice expands into the gravel as it freezes.

Therefore, if the purpose of the gravel is to reduce foundation wall pressure, and eliminate the potential for freeze/thaw pressure, it will likely be successful. The gravel will not eliminate groundwater because there is no perimeter drain, however that does not appear to be the reason for the installation.


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## mnp13 (Jan 16, 2007)

There is some sort of drain system in the basement, and there is a sump pump. Of course, if the large areas of gravel fill with water, that water has to go somewhere - and my thought is that it's going to go to the path of least resistance which is the basement wall. Assuming the drain channel in the basement is done correctly, that water should end up in the sump pump but that has the potential to be a _lot_ of water, doesn't it? Sump pump failure (power outage or mechanical) would be a disaster if that's the case. 

But as I said earlier, the gravel itself runs a few feet down the basement wall and is more than a foot wide. Once that goes the entire length of the house, you have the potential for hundreds of gallons of water in that gravel, sitting against the wall looking for somewhere to go. The whole system would make sense to me if there was a drain at the bottom to move the water elsewhere, but there isn't and there won't be.

In any case, this is all theoretical, since it's not my house or my project... and it was quite clearly put that my opinion on the matter wasn't needed. lol


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## jklingel (Dec 21, 2008)

4just1don said:


> Now how do I keep the water out of the top from running down?? thought of plastic on good grade with dirt on it,,,then a bark cover since 4 or 6 inches of dirt wont grow anything with plastic under it...is this the BEST cap??? or pour concrete 2 ' around whole house????


 We did just that over my son's water tank, as recommended by the water guy. Weeds will grow there, I suspect. His weeds are feet tall. I have had plastic lining a french drain, with rocks inside, that I've used for gutters for 35 yrs, and weeds grow in it if I don't pull them. A few years ago I was "a bit remiss" on cleaning the little bit of normal gutter we have, and when I went up the ladder to pull the usual leaves, I had two birch trees growing, one about a foot tall. I have no fear of SOME plant growing in 6" of dirt, and I'll bet grass will, too.


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## stadry (Jun 20, 2009)

' underground pipe was disconnected (that was fixed.) ' - was that part of a foundation drain system ? patching the crack's fine IF they also waterproofed the wall,,, otherwise i don't understand it either & we do this work for a living :no: however, my lack of comprehension has rarely prevented my from expressing an opinion :laughing: i suspect it was the owner's wallet that was the deciding factor :yes:


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## mnp13 (Jan 16, 2007)

Owners wallet didn't have anything to do with it - they are doing all of the work themselves. The underground pipe is the pipe that runs from the downspout on the gutters to the drainage system. 

They patched the wall, I have no idea if it was waterproofed. They didn't expose the entire wall, so waterproofing just one section wouldn't make much sense I don't think. 

I'm going to see her today, I might bring it up, but I'll have to test the waters a bit. I don't want to step on the boyfriend's toes... lol


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## Ron6519 (Mar 28, 2007)

You said there was an underground pipe that was disconnected and that it was fixed. 
Were these the perimeter drains at the foundation base?


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## mnp13 (Jan 16, 2007)

Ron6519 said:


> You said there was an underground pipe that was disconnected and that it was fixed.
> Were these the perimeter drains at the foundation base?


No. It was the underground pipe that the downspouts from the gutters attach to.



> They patched the wall, I have no idea if it was waterproofed. They didn't expose the entire wall, so waterproofing just one section wouldn't make much sense I don't think.


The wall was waterproofed in the section that they exposed. They did not dig to the bottom of the wall, just to the bottom of the crack, about two feet above the bottom.


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## concretemasonry (Oct 10, 2006)

It sounds like the crack instigated a "patch job" and probably waterproofed just that area.

In the future, the downspouts should never be connected to perimeter drain system at the level of the bottom of the footing (either located inside, outside or both). Down spouts can easily cause basement flooding due to the rapid amount of water at any one time and the debris that could clog a good drain tile system.

Dick


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## J self-builder (Mar 14, 2021)

Years later, I have to interject this dead thread to point new viewers toward “Frost Protected Shallow Foundations” so that it might dawn on them not to leave airspace next to the concrete foundation via gravel. Yes it drains, both air and water. So consider what happens when cold air is in the space.... I suggest laying 2 inch rigid foam paneling, the pink stuff in my region, against the foundation before backfilling with rock, and YES make sure drainage is attended to, even if you need a deeper pit in one spot with a sump pump set up. 
As a FPSF builder, I can say the foam is an unbelievably simple addition to foundations that everyone should be doing. Side note, in an FPSF you are planning for heat to exit the house thru the air in the gravel layers, thus protecting the house from heaving thru freeze/thaw. The foam creates a huge difference below ground, keeping about a foot or so wide perimeter of soil unfrozen thru the winter. It’s impressive to see in the dead of winter. FPSF basically makes a heat trap out of the foundation. Gravel alone is just not nearly as effective at making a temperature barrier so don’t miss out on the upgrade to foam while your down there.


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