? for emmgjld, cracks in basement in Colorado 1

[rkash74]

this is actually a question from a homeowner to emmgjld because I live in Denver and you seem familiar with our semi-arid, sometimes wet area.

we've had significant cracking in our basement. 2 structural engineers have said it is not structural but the house has clearly shifted and some flooring has settled. we connected our roof gutter spouts to a french drain on one side, but need to figure out what we can do on the other side to address water. i'd like some thought on repair.

but my big question is that we had a realtor out who said that once water is under a foundation it "mascerates" the foundation, essentially destroying it even if you fix the drainage issues. is that true? does water stay forever under a foundation in dry Colorado?

 

[emmgjld]

I am assuming your fingers get out of control on your keyboard, similar to my experiences ...
did you mean macerate;
1. to soften or separate into parts by steeping in a liquid.
2. to soften or decompose (food) by the action of a solvent.
3. to cause to grow thin.

This is not a word I have heard used to describe soil reaction when water is introduced, whether soil expansion, settlement or collapse.

In our semi-arid climate (Denver is somewhat wetter than Grand Junction but my condition is only more severe than yours), we deal with soils and soft rocks with a recent (last several 1000 years) and a geologic history of being fairly dry. Development & Landscaping tend to create a wetter climate. This climate is maintained by continued water application (think irrigation, changed drainage conditions), decreased opportunity for soil drying (think pavements, slabs, structures & landscaping all of which can hinder evaporation). SO ... once the water has entered the soil/soft rock, it is probably there to stay. Drainage & irrigation control usually works to prevent a worsening of condition. Extreme drainage & irrigation control MAY work to lower the soil moisture content, if conditions are optimal.

I have seen several fields in my area which were taken out of irrigation, the seasonal water table about 5-10 feet below the ground surface and were allowed to sit fallow for 8-10 years. Ground cracking occurred (open cracking measured to 20+ feet) & our drill holes indicated low moisture soils to about 25 feet and the water table at 50+ feet. Irrigated fields & high seasonal water tables within 700 feet. No significant water imput & allowing evaporation over the entire tract resulted in significant, deep drying. Being able to reproduce this condition in a developed area is unrealistic and I suspect your existing subsurface soil moisture condition should be considered as permanent.

You mention we connected our roof gutter spouts to a french drain on one side. Are you draining the roof drainage into the ground or using piping to remove the water to a positive discharge? Draining or 'seeping' into the ground is very different from removing the water.

You mention some flooring has settled, is this relative to the rest of the structure? and do you know what the actual foundation soils are? and what type of foundation you have?

 

[rkash74]

Thanks. Macerate (like what you do to strawberries on a shortcake) was the term the realtor used.

The roof gutters drain out to a cap in the front yard, but it was hard to get it much lower than the side yard where the water had been pooling.

I haven't had a soil analysis done but I have been told we likely have a lot of bentonite.

Our basement is floating slab. In one unfinished room the crack runs perpendicular to the load bearing wall and has settled about an inch. 2 structural engineers have looked at it and said it wasn't structural but thought it was strange. We've also had some bowing visible in some walls and ceiling in the basement, that's minor.

The realtor and a Basement Systems salesman said that once water has gotten under the foundation and once the house has moved it will continue moving. The realtor suggested selling and the Basement Systems guy proposed anchors in the walls.

I was hoping I could stop more water from coming down around the foundation and seal the cracks. But my wife is worried that this isn't fixable and we should sell it, disclose the issues and let someone else worry about it.

I know you can't give a real specific and definitive answer, but have you seen people able to fix issues like this and not affect the house in the future?

 

[oldestguy]

Your problem is common in Denver due to high plasticity clay, with the mineral bentonite. An experienced geotechnical engineer would be able to advise as to what to do. It is not an easy fix. One experienced engineer in your area has a solution that you may try. Recognizing the seasonal effects, he goes to his basement twice a year and readjusts the support columns. No correction but living with it.

 

[oldestguy]

One more comment. Drying causes shrinkage, thus foundation settlement, Wetting causes expansion, thus, lifting of foundation. The funny words used by realtors are meaningless. This drying shrinkage and wetting expansion can go very deep, far below the foundation, far below what you can fix. However, there are treatments to the clay that make it less active as to shrink and expansion, generally taking an experienced contractor. Do not just take any body's word for what to do, but ask any contractor to provide references as to past successful work. Any work you can do to direct water away from the foundation may help, but wont solve things. Any trees nearby will draw water out and can "assist" in drying in drought weather times, but won't completely cure if removed. In some areas one can add water to the area (mainly at trees) to minimize drying effects, but that means every summer, forever. I've seen that "fix" work in Wisconsin, but not so sure about your area. Remember, any help must be from an experienced outfit, because there are many that will take your money and won't adress the real cause.

 

[emmgjld]

The comments by oldestguy are appropriate for your problem.

I find it interesting that your slab seems down, relative to the basement walls. This is not the usual condition in the 'northern Front Range' but is common in the Pueblo area and the drier portions of the Western Slope. The 'settled' slab is typical of water affecting the outer foundation portions first and then possibly not sufficient water to severely affect the interior portions, such as slabs. In many cases, the slab has not settled, but the exterior foundation has 'heaved' more.

I have seen these problems dealt with in a reasonably satisfying manner. Much depends on the your total situation. Seasonal type wetting/drying may be controllable, with may limit seasonal heaving/shrinking. A number of questions need to be asked so you can provide sufficient information to contractors and consultants.
1 - What are your soils conditions? Will probably require drill holes or test pits.
2 - What is your foundation type, any design, actual construction?
3 - What is the actual history of the structure?
4 - What are the drainage conditions of the site, which probably are affecting the structure within 50' to 200'? This can be the most critical subject and usually determines whether the problem can be dealt with small bucks or big bucks. If drainage cannot be improved or at least stabilized, then your problem gets expensive.
5 - What are the probable sources of water to the foundations soils? obvious & not obvious.

 

[rkash74]

Well, the drainage was bad when we moved in a year ago, but no real cracks. After we moved in we had the worst storms since the 70s. There were no cracks at that time, but I did see some water leaking into the basement at a spot where there was a prior water stain. Last Christmas we saw some cracking in the room and then this past Veterans Day it seems to have settled significantly. That day the temperature had about a 40 point swing. 70s in the day to about freezing. I think I can keep more water from getting under the foundation but wanted to see if it would continue to crack after I fix the drainage.

Would I need to contact a civil engineer? Could a state government department help with some answers?

 

[oldestguy]

OG here again:

I don't suspect it, but with slab settlement , there may have been a break in a drain line from the house, eroding out a sand bedding under the slab. This I doubt, but one never know unless he checks. Again an experienced geotechnical civil engineer would be the expert to use. Such a person in your area likely is experienced with the problems of shrinkage and expansion of soil there. A civil engineer not specializing in the local soil problems is not likely to be suitable. I know, since this aspect of foundations usually is not taught in colleges and it usually is not something in practice they run up against. I know, having had to "solve" the "unknown cause" left unanswered by such engineers.

As to a government agency, see if you can find a local office of the US Bureau of Reclamation. I think they do have an office in Salt Lake City for your area. They have had extensive experience with these highly expansive clays under the linings of irrigation canals. However, if they also deal with their structure, I do not know. The local building permit and building inspection people may be of some help, but unlikely.

In Texas where this problem also occurs, there are contractors that inject lime to change the mineral properties, but whether or not there are any in your area, the experienced geotech engineer would know.

The goal I usually end up with on these conditions is to keep moisture the same, no adding and no drying, generally acceptable but never a complete solution. A common source of shrinkage has been fast growing trees nearby, so don't overlook that.

 

[rkash74]

We had our drain scoped and they found no breaks. That was an early concern, but I'm starting to think that there is water seeping in along a concrete pad in the back that was added for a hot tub and it has since sunk several inches (the hot tub has since been removed, before we moved in)

The spot where the pad meets the original patio is where we've seen the water in the basement, but only during that intense period of rains.

 

[oldestguy]

OG again:
Before your geotech engineer shows up, take some photos, preferably with some reference device in the photo, such as yard sticks, clear visibility on ruler or measuring tape. These, then would be reference photos for possible future movements. Ideally I'd take a transit-level in and map the elevation of the basement floor and the various foundations. However, photos with reference devices in them is better than nothing. One home made leveling "instrument" is a garden hose fitted with a 3 foot length of clear tubing on each end. Fill it with water and make sure all air is out of it, by holding the two clear tubes side by side. Then, keep one near a "reference" place, such as a floor point that seems to be affected least, or a foundation wall, as your bench mark (BM). Then, taking the other end to various known (by measuring from walls) points and read the height to the bottom of the meniscus of the water there. At the same time measure from the reference point (BM) up to the meniscus of the water in the tube there. The difference in these readings is the elevation difference from the bench mark. Doing this at several known points on the floor will give you a form of contour map of the floor. You also can use the same method outside, or in upper floors if you want to measure elevation differences there.

Don't be fixed on the firm idea of occasional water entering and causing all the trouble, since that, as the cause, is very rare. Instead, the long term moisture changes in the soil to very deep depths (like 40 feet or so) are most likely your problem, in spite of occasional heavy rain. Bentonite clay is very active with its affinity for water, but it has low permeabilty. Thus, the volume changes are very slow in happening. A bone dry bentonite clay will swell to 16 times its original volume, given enough water and little confining resistance. When confined it really takes major pressure to stop it expanding. Of course, take away the water and it reverses this volume change. Enuff preaching.