Watering the foundation

Darren Wright

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Seems like we've gone from feast to famine lately with rain. I think I may have gotten a small sprinkle today, but has been pretty dry and predicted to be in the high 90's the next two weeks. I notice several large cracks starting to show around the front yard while walking around last night.

Given that our house has had some foundation issues in the past, I don't want to take any chances, so I ended up dragging out some hoses and watering the foundation. Anyone else do this? I'm considering just having sprinklers put around the house itself, to water the flower beds but also keep the ground around the house a little more stable.
 
What kind of soil is your house on? What kind of foundation problems did you have in the past? Do you have a basement? Where I come from (which is definitely not KC), watering around a foundation is often a recipe for problems. But out here, we can have either uncompacted native sandy soils or expanding clays. Neither benefit from water, at least not after a building has been placed on them.

There's an expensive gated community here in ABQ that was built on native sandy soils. The soil was compacted to a depth of 20' to 30', which is most cases is ample for supporting a house. However, some of the homeowners felt compelled to disregard the soils engineer's recommendations and installed landscaping that required a lot of irrigation. Over time, some of these expensive houses started to settle, because water had reached the uncompacted native soils, which started to collapse. One house we investigated was watering the law with the equivalent of 8" of rain daily. We did a drilling investigation that found saturated native soils 40' deep. That house had 8" of elevation differential from one side of the living room to the other.

I also did an investigation once on an Apache reservation in Arizona where a lot of the government-supplied houses were cracking badly. At first it was thought the houses were settling, but we determined that they were built on expanding clay, which was swelling underneath the houses. This normally wouldn't be a problem if rainwater was directed away from the edges of the house, but at the houses where we found the problem, the site grading had been changed and water was pooling right beside the house. It also didn't help that there were no rain gutters installed on these low-cost houses, so the water was going everywhere instead of being directed away from the foundation.

Probably way more info than you were asking for, but as someone who used to make a living investigating failed foundations, when someone says "watering the foundation" it tends to send a flag up for me. ;)
 
Thinking about this a bit more, I suspect the cracks you're seeing are merely surface cracks, and not an indication of deep movement. I honestly can't think of any case where adding moisture would help stabilize the soil under a structure. (On a hillside under specific conditions might be another story.) Let me know what kind of soil and foundation you have, and I'll consult my resident soils and foundation engineer (my dad), who does have some experience with KCMO soil conditions.
 
Vaughn you made me laugh. Back in SA good old gov did the same on low cost housing. Built it on clay. Units were done as a job creation project. Note 99% of housing in SA is built English style with double wall brick outer wall and single wall brick inner wall. Then walls are plastered with cement and roughed over with a hard broom. Then painted with cheap PVA.

Well banks got the shock of their life when the tenants decided (after getting no joy from authorities or builders) that they no longer wanted the house or the mortgage that went with it at any price so they went into the banks gave the keys back when the huge cracks began to appear at joints and through complete walls.

I loved it because it was better than occupy wall street. These simple people just put the keys on the counter and left the bank with the bag. Pointless going after them they had pretty much nothing to go after them for. Man I loved it real People Power. At the time I felt like going out and cheering them on. Sometimes it takes simple folk to show the way it should be done. :rofl:
 
My yard gets cracks when it's dry. After I had to walk around to find a sprinkler valve that was leaking by, I figured out every trench line for the sprinkler system just about had a crack open where it was run. Our house is on mostly clay below the topsoil.
 
The damage that was fixed on the house was about where they filled for when the septic lines were, so I suspect that the settlement there caused the footings to settle in that area. They ran supports down to bedrock and pinned the walls down that side according to the documentation from the previous owner.

I base my watering off of what most home inspectors say around here, which is that they've never seen a house with foundation issues where the home had a sprinkler system. I've been told that by many builders as well, including my dad. All say even if you don't water your yard, at least water your foundation as the changes in the soil will eventually cause issues.
 
We are in an area of shrink-swell soils. New homes require soils to be testing for shrink-swell and special treatment for foundations where appropriate. They can be a problem and IMHO, if you can stabilize the clay to prevent the damage caused by the extremes of wet/dry you prevent serious issues later on.
 
...I base my watering off of what most home inspectors say around here, which is that they've never seen a house with foundation issues where the home had a sprinkler system. I've been told that by many builders as well, including my dad. All say even if you don't water your yard, at least water your foundation as the changes in the soil will eventually cause issues.

I'd go with with what the locals recommend. :thumb: Still not sure I understand why it works...I'll have to ask my dad to educate me. ;)
 
What Ted mentioned is the way I understood it. When it gets dry the soil drys and compacts, but should that happen too deep it could affect the footings/foundation on the structure. When the soil re-hydrates it may cause some areas of the foundation to stress and crack.

I know my dad mentioned it about my last house, I had an abnormal amount of cracks in the basement floor. The electrical company had severed one of the drain tiles at the bottom of the foundation on one side, which my builder later fixed. However the prior pressure from the saturated soil under the basement floor had heaved causing many of the cracks I was seeing. I had a couple of times that the ground became so saturated that the basement flooded via the rough-in for the shower drain down there (this was a walk-out basement, entire back half was above the ground). We later installed a sump-pump to prevent anymore flooding.
 
...When it gets dry the soil drys and compacts...

Minor clarification: It might shrink when it dries, but it won't actually compact*. The shrinking will cause cracks in the soil, which could allow water to get into the deeper soils and make them swell. I suspect that's where the foundation problems came from. (Still need to ping this off my dad for more info.)




* To compact soil (in other words, to get the maximum number of pounds of it into a cubic foot), it's necessary to mix water with it. The amount of water varies depending on the soil type, but every soil type will have a optimum moisture content needed to get the maximum compaction. I've run hundreds (if not thousands) of the lab tests where this optimum moisture and max density is determined.

http://en.wikipedia.org/wiki/Proctor_compaction_test

I'm pretty amazed that I still remembered the ASTM number (D1557).
 
Had a chance to talk with my dad about this, and here's what I learned:

In many parts of the country, native clay soils tend to never completely dry out. They naturally reach a moisture equilibrium between the plastic limit and the liquid limit and typical weather patterns keep things that way. In simple terms, the clay stays moist, but neither too wet nor too dry. If the soil does happen to dry out much below the plastic limit, it will shrink and buildings built on it can settle. So the upshot is yes, in many parts of the country it does make sense to water moderately around your house's foundation if it starts to dry out severely.

Here in the desert southwest, where virtually all of my soil experience has come from, most of the native clay soils have become completely dried out over the eons. Any settling that would typically happen did so ages ago. When water is introduced to clays in this condition, they can expand and actually lift a building. My dad mentioned one sample that someone in his lab once encountered that expanded with a force equivalent to 12,000 psi. So out here, watering a foundation could be a bad thing.
 
In Houston, they call the soil Gumbo. It's a kind of silty clay. Terrible stuff for gardening, worse for houses. When it gets wet, it expands, when it dries, it shrinks. Noticeably. And once it's really dry, it actually repels water, since it's got so little organic matter in it.

Normally, its not a real problem, unless you're a gardener. It swells and contracts, pretty evenly. But in a dry, hot summer, when part of the ground is in the sun most of the day, and part is in the shade...

I never saw people watering their foundation in California, or here in the east. At first, when I saw it in Houston, I thought they were just watering their lawns oddly. But then I noticed they were letting their grass go brown away from the house...

Thanks,

Bill
 
Here in the desert southwest, where virtually all of my soil experience has come from, most of the native clay soils have become completely dried out over the eons. Any settling that would typically happen did so ages ago.

Even better they've often been mixed with limestone over the ages and have formed something akin to claycrete. Ah the remembered joys of picking axing ditches for the sprinkler system for my first house.. http://en.wikipedia.org/wiki/Caliche.

Pretty interesting thread, had never heard of watering a foundation either.
 
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