To “MudJack” or Not

(after slab foundation repairs)

If after a slab foundation is repaired by installing piers AND the slab is lifted upwards as part of the repairs, a void space will be created between the bottom of the slab and the dirt. The question to be discussed in this blog is: should the void space be filled (mudjacked) or not. The answer is: it depends.

Several years ago, most foundation repair companies (in the North Texas area) automatically included in their proposals the cost to inject a grout slurry mix into the void space (usually referred to as mudjacking). The traditional slurry mix consists of cement, soil and water (which is a very low grade of concrete) that can be pumped into the void spaces. The slurry then hardens and will provide support to the slab (as the dirt used to before the lifting of the foundation).

However, now days, mudjacking after foundation repair does not seem to be done as frequently as it once was. I suspect that there are several reasons for this but one of them could be that if the slab was built on expansive clay, some believe that it is better to leave a void space between the bottom of the slab and the dirt. This allows the clay to expand some without impacting the slab (depending on how big the separation is and how expansive the clay is).

I know of a foundation repair contractor who during the drought of 2006, lifted several slab foundations and then completely filled the void space with slurry. Unfortunately, when the rains returned and the expansive clay soils expanded, the foundations heaved up off the piers. Depending on the severity of the upheaval, this is very difficult to remedy.

Because of this potential for upheaval when a slab is built on expansive clay, many engineers do not require that the void space be filled with slurry.

However, there are other engineers who insist that all voids be filled. Their position is based on the true premise that a slab-on-grade foundation (slab that is supported by the dirt) was designed by the original engineer to be fully supported, so all void spaces should be filled.

Unless circumstances dictate otherwise, I typically do not recommend filling the void left between the soil and the slab after a foundation is lifted. This decision is based on the assumption that expansive clay soils may eventually expand and heave the slab upwards. Yes, there is a risk that the slab may not be strong enough to span above a void space without deflecting downward. IF this deflection occurs, then the void will need to be filled (with a slurry or polyurethane foam).

To restate the issue: there is a risk in NOT mudjacking (not filling the void) AND there is a risk in mudjacking (filling the void). To me, the more reasonable risk is to not mudjack unless a problem develops and the unsupported portion of the slab deflects downward. If this deflection occurs, then mudjacking (or filling the void with polyurethane foam) will need to be done. It should be said that the downward deflection of the slab may not occur for months (years) after the foundation work has been completed. Even though I have never experienced this on my projects (which includes thousands of repairs to slabs), it can potentially occur.

However, if the void space is filled soon after lifting the slab and the clay expands and pushes the slab upwards, there usually is not much that can be done that is financially reasonable (except wait and hope the soils will eventually shrink back down). This latter course of action is technically the correct thing to do but it also has the higher risk of upheaval of the slab if that slab is on expansive clay soil.

I recommend that the homeowner discuss this issue with his/her engineer and with the foundation repair company.



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Posted by on January 2, 2017 in foundation repair


Why Are Texas Homeowners Told That They Need To Add Water To The Soil Around Their Foundation? Part 3

In my previous two blogs (Parts 1& 2), I discussed the reasons for the “requirement” for Texas homeowners to add water to the soils around their slab foundation. It is suggested that these two documents be read in conjunction with Part 3.

Buried Drip Irrigation Systems:
The installation of a buried drip system (hooked up to the lawn irrigation system) to water the soils around the foundation is becoming more common and is certainly more convenient than using soaker hoses that lay on the surface.

However, I have heard of a few examples where a homeowner installed a buried drip irrigation system and immediately began an aggressive watering program. Unfortunately, the sudden increase in moisture caused the clay soils to expand and heaved their slab foundation upward. However, I have also seen a homeowner move into a residence and began “normal” (not aggressive) watering of the lawn and foundation and their foundation still heaved upwards several inches.

Too much water can be just as bad as too little. In fact, too much water in the “right” soil conditions (dry expansive clay soils) can lead to catastrophic results, causing upheaval of the foundation. Unfortunately, since soil conditions in North Texas vary from one neighborhood to another, there is no single watering solution that will cover all areas.

I must state again that the homeowner must exercise caution when the slab foundation is on dry expansive clay soils because too much water can expand the soil and damage the foundation.

It is best to allow Mother Nature increase the soil moisture content (for example, during or soon after the normal winter/spring rains) and then the homeowner starts his water program before the soils begin to dry. For example, as I am writing this blog, the soils in North Texas (DFW area and north) are saturated because of all the rain we have had this winter. At my home, I could not add any more water to the dirt, even if I wanted to. Because of this, generally speaking, the slab foundations in North Texas are currently performing as good as they have in years.

I do not consider myself an “expert” on buried drip irrigation systems nor have I studied how the industry is currently installing these drip systems but a few miscellaneous comments / observations are:

• The few foundation drip systems I have seen consist of small diameter black tubing that is buried a few inches from the foundation. It seems to me that this thin wall tubing could easily be cut with a shovel. If this occurred, it could be similar to having a plumbing leak under/near the slab. It would be better if the drip line is made up of thicker wall pipe that would be harder to damage.

• Some of the drip systems I have seen are buried only inches away from the foundation and only a few inches deep. I prefer that a drip system be buried a foot or so deep and be about 18” from the foundation. (If the drip system is to be installed in an area where the ground surface is sharply sloped, the placement of the drip line may need to be modified to minimize the amount of water running downhill away from the house.)

• The drip line should be marked to alert anyone digging in the area that there is plumbing below.

• I have seen one buried drip system where the drip line is installed in a bed of pea gravel. This would not only aid in alerting someone digging in the area that there is a plumbing line below but it would help disperse the water. If this technique is used by a homeowner, I recommend wrapping the pea gravel in a drainage fabric to keep the gravel from silting up.

• Obviously, the system I generally described above is much more expensive than the normal drip systems that I have seen recently.

• I have heard of some buried drip tubing lines that have been chewed on by varmints.

• I have also heard about some types of emitters, if buried, will eventually get clogged up with roots.

• The drip system must be monitored for leaks.

• If the clay soil around a foundation is in a desiccated state, do NOT suddenly put a lot of water into the soils. To do so, may cause      permanent upheaval of the slab. Upheaval can be a most difficult, if not impossible, thing to attempt to remedy.

• It is generally accepted that a homeowner should check to see if the soil is pulling away (separating) from the foundation. If so, it is an indication that the soil is becoming desiccated and water should be added to the soil. DO NOT pour water down the separation!

I have witnessed a few newly constructed homes where the slab was constructed on expansive, dry clay soils and after the homeowner began his normal watering of the landscaping with a sprinkler system, the clay soils expanded and heaved their homes upward a few inches.

There is not an easy answer or remedy for this situation. Hopefully, the reader is not in this predicament, but if he is, he should contact the builder and/or the structural engineer who designed his foundation (or the geotechnical engineer who conducted the soil study) and ask them for advice.

• I once had a client who used a moisture meter to measure the soil moisture content around his foundation once a week. If an area was dry, he would add water.

• To repeat: Too much water can be just as bad as too little; even worse, depending on your soil conditions. Determining how much water to add to the soils is somewhat subjective and requires some experimentation and there is no “one size fits all” answer. In other words, there are many, many variables involved in determining how much, how often to water the soils around the foundation.

I highly recommend that the homeowner retain the services of an experienced engineer to review his particular situation and make recommendations as to how much to “water” the soils (even he will guess, albeit it will be an educated guess).

• Even though the theory of keeping the soil around the foundation at a constant moisture content is valid, practically speaking, it is a difficult thing to do.

• Because of the potential problems with a buried drip system for the foundation, I am not yet a fan.

Proceed with caution no matter what system you use to water the clay soils around your foundation!

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Posted by on April 25, 2015 in foundation repair


Why Are Texas Homeowners Told That They Need To Add Water to the Soil Around Their Foundation? Part 2

In my previous blog (Part1), I discussed the “requirement” for Texas homeowners to add water to the soils around their slab foundation. This is being done to attempt to limit foundation movement caused by clay soils drying out.

Slab foundations in North Texas are usually not installed in a stable bearing stratum (like rock) but are installed on the surface of expansive clay. Being installed on the surface ensures that the foundation is in (and on top of) the Active Zone. The Active Zone is that depth below the ground surface where the moisture content does not vary. The soil below this Active Zone is reasonably stable, but the soil above the Zone contracts and swells in a cyclical manner, depending on the season (wet/dry). This shrink / swell can push a slab foundation around.

So the goal of adding water to the clay soils around the foundation is to attempt to keep the moisture content of the clay in the Active Zone as constant as possible. Doing this minimizes (but does not necessarily eliminate) the potential for slab settlement. at least the settlement that is caused by the soils becoming desiccated. (Slabs settle for reasons other than desiccation.)

There are three methods commonly used by homeowners to add water to the clay.

Soaker Hoses
The most common method of maintaining the soil moisture is by laying soaker hoses on top of the ground around the foundation. Even though this technique has its difficulties, it is the simplest and least expensive. It also makes it easy to see if the hoses have been damaged and need replacement. It is usually recommended that the hoses be placed 18” to 24” from the foundation.

One problem with soaker hoses laid on top of the ground is that a lot of the water can be lost to evaporation or run off. Another problem is that they get kicked around and cut up by the landscaping crew.

Some homeowners bury the soaker hose which protects them from lawn mowers, but this makes it more difficult to see if they have been cut, damaged, etc.

Automatic Lawn Sprinkler (Irrigation) System.
If a homeowner is planning to have an irrigation system installed, here are a few things to discuss with the irrigation (licensed) specialist:

• If I were going to have a sprinkler system installed, I would have a supply line installed parallel to and about 4 or 5 feet from the foundation (to minimize the bad effects if a leak developed in the system). I would then install short radial lines to reach the foundation area (with the sprinkler head about 6” or so from the foundation).
• I would not install the water supply line only a few inches from the foundation.
• Regularly check the sprinkler system for leaks, including at the valves.
• In the Dallas / Ft. Worth area, I would install the irrigation pipes at least 12” below the surface to minimize the danger of an extended period of freezing weather. However, the irrigation technician will know the minimum depth. I had a neighbor whose new sprinkler system was buried only 8” and portions of it froze during a particularly cold winter. Your local city building code department probably has minimum guidelines on this.
• If the purpose of the irrigation system is to keep the soils near the foundation at a constant moisture content, then there should be 3 or 4 zones dedicated to the foundation only (possibly more depending on the size of the house). This way, it is not necessary to water the entire yard when the foundation soils need water.
• Do not allow the sprinklers to spray water on the brick/siding.
•DO NOT suddenly begin an aggressive watering program if the clay soils are in a desiccated state (like during a drought or in the dry summer months). In other words, do not suddenly put a lot of water into the clay soils around your foundation. To do so, can cause upheaval of the slab. It is best to allow Mother Nature to rehydrate the soils during the winter/spring months and then start a watering program prior to the summer drought kicking in.
• Too many homeowners water only enough to keep the upper few inches of soil moist; this is inadequate.
• One typical indicator that the soil around a foundation needs moisture is that the soil begins to pull away from the foundation. When this occurs, moisture is needed: do not pour water into the gap!
• During the prolonged summer drought, it may be necessary to water the soil around the foundation several times a week. A word of caution though – do not suddenly overwater dry expansive clays! The goal is to keep the soil near and under the foundation at a consistent moisture content (neither wet and/or muddy nor dry and cracked).

I  have seen homeowners who had just purchased their homes and began their watering the soil program only to cause the clay to expand, heaving their foundation upwards. They later found out that the soils around the foundation had not been “watered” for months and were in a desiccated condition. I do not have an answer to this dilemma. My advice is to be careful and be gradual in your watering program. As stated elsewhere in this blog, if it is new home, talk with the builder and/or his engineer about their recommended watering  guidelines. If an older home, let Mother Nature rehydrate the soils, then you start your watering program.

In the next blog, I will discuss the pros and cons of a buried drip irrigation system.

For additional information, go to

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Posted by on February 13, 2015 in foundation repair


Why Are Texas Homeowners Told That They Need To Add Water To The Soil Around Their Foundation? Part 1

As is well known by most homeowners in North Central Texas, the foundations for our homes are many times constructed on expansive clay soils. The problem is that clay soils shrink when they dry out and swell when they experience an increase in its moisture content and this shrink / swell of the soils can easily push a slab foundation around. This has cost Texas homeowners millions and millions of dollars in repairs.

In the North Texas area, the soils tend to become desiccated in the dry summer months. There is a depth below the surface which is called the “Moisture Active Zone”. This zone is typically considered to be about 15 (or so) feet deep but the actual depth varies depending on many factors (soil conditions, rain, drought, trees, exposure to sun/wind, etc.).

Below the active zone, the moisture content of the soil generally does not change. However, above the active zone, it does. As the soil moisture changes, so does the volume of the clay soils and a structure built in (or on top of) the active zone is prone to move. This includes almost all slab foundations.

So, in much of Texas, it is commonly said that to prevent (at least minimize) the movement of a slab foundation, a homeowner must maintain the soil moisture content around the slab foundation at a constant rate (year around). This means attempting to replace the moisture in the active zone that was lost because of desiccation caused by environmental influences. This is done in the dry seasons by adding water to the soils. Maintaining the soil moisture content at a constant value is an easy thing to say but is difficult to do, especially during times of extended drought.

One difficulty for homeowners is that there is no “formula” available to tell them how much water they need to add per day/week to keep the soil stable, i.e., to keep the soil volume constant. There are too many variables.

This is because environmental and soil conditions vary from neighborhood to neighborhood. Also, the rigidity of one slab is typically different than another. The more rigid a slab is, the better able it is to overcome the movements of the soils caused by the variations in the seasonal moisture conditions (rainy season vs. dry season).

I am asked regularly: “can the builders build a slab that does not move”? The short answer is yes. The basic reason most slab foundations in North Texas move is that they are not founded in a stable bearing stratum which is below the moisture active zone. (There are other reasons a slab foundation move but moisture variation is the subject of this blog.)

So, to answer the primary question posed in the title of this blog: homeowners are told to add water to the soils supporting their foundation because most slab foundations are based in the active zone where the soil moisture content varies because these soils are susceptible to desiccation during the hot, dry summer months (and during other periods of drought).

I should say that I have observed a few homes with slab foundations where the homeowners appeared to be very diligent about applying water to the soils, but their foundations still moved and further (and more expensive) remedial efforts were required. Also, a word of caution: I have also seen homes where the homeowners started a vigorous watering program when the soils supporting his foundation were dry, expansive clays and the sudden increase in the moisture content of the clays caused the clay to expand and pushed (heaved) the slab up significantly. This upheaval is a problem.

The next blog will discuss the various methods commonly used to add water to the soils around the foundation.

GeoDynamics Engineering

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Posted by on February 1, 2015 in foundation repair


House “Flippers”

Over the years, I have inspected the foundation of homes that had been purchased by investors. The investors remodeled the interior / exteriors and brought them up to a “new car smell” standard and sold them. Obviously, I am somewhat jaded by some of the things I have seen “flippers” do. However, on the other hand, I have seen some investors who not only do a wonderful job on the “new car smell” upgrades but  also do a good job on repairing the foundation (if needed).

Since I get involved in only foundation problems (in North Texas), my comments will center around the Good, Bad and the Ugly aspects of buying a home that has foundation problems from an investor. (I should also say that I have also seen some long time homeowners / occupants of a home act the same way as the “flippers” do – see the last example of “The Ugly”.)

The Good

One home I inspected was owned by an investor who recognized that foundation repair was needed on a home she was going to “flip”. She contacted an engineer to design the foundation repairs. She hired a reputable foundation repair company to do the work. Once the foundation work was completed, she had the engineer return and review the work and write a compliance letter to pass on to a prospective buyer.

Included in her sales package to any prospective purchaser was a copy of the engineer’s reports, the foundation repair company’s warranty documents and a copy of the sub slab plumbing leak test (done after the foundation work was completed).

She then installed new floors and remodeled the kitchen and baths.

The home rapidly sold at the asking price.

The Bad

Several months ago, I inspected the foundation of a 1500 sq ft home with a slab foundation. The buyer (my client) loved the home because the investor had installed new wood floors, new kitchen granite counter tops and removed some walls to make an open interior living room/dining room and kitchen. He had also recently had foundation work performed. The investor had retained an engineer to design the foundation repair. The engineer had recommended the installation of numerous piers around the exterior and throughout the interior.

He also specified that the foundation be raised to within a specific range.

The investor hired a foundation repair company to install the piers supposedly in accordance with the engineer’s specifications. (It was later determined by my client that the foundation repair contractor did not obtain a building permit as required by the city.) Once the foundation was “repaired” the owner completely remodeled the two bathrooms and installed new wood floors.

My inspection found that the foundation in several of the rooms was still significantly out of level, with some doors so much out of level that they could not be closed. Also, there was no evidence that the foundation repair engineer had ever reviewed the foundation repairs as they was being done or afterward.

I advised my client to have the owner (investor) get his engineer to issue a letter certifying that the foundation work was done to his specifications or if not, describe what needed to be done to make it so. I also advised my client that to attempt to raise the foundation up to an acceptable level would probably damage the remodeled bathrooms (including the shower tile walls); so some cosmetic repairs would need to be done after the foundation was lifted up.

The owner was not willing to do these things so my client wisely backed out of the deal.

The Ugly

I once inspected a small home for a young couple who had just purchased their first home and within a few weeks after they moved in, large cracks began appearing in the sheetrock. In my inspection I found that the doors were generally level but that the slab was over 6″ out of level. It was obvious that the foundation was (and had been) unstable.

I asked them if they had a copy of the report from their General Home Inspector, made prior to purchasing the home. They said that their realtor told them that an inspection was not necessary so they did not have the home inspected. (The realtor had them sign a document that said they did not want an inspection.)

They found out by talking to a neighbor that the previous owner was a professional painter and that he would completely paint the interior of the home two times a year and had done so prior to putting the home on the market. (He also had rehung the interior doors.)

To repair the foundation would require about $25k of piers which they could not afford.

My Advice To a Buyer of a Home in North Texas

Get all documents from the seller that concern foundation problems. If the owner says that there has not been any foundation work done or an engineering inspection done on the foundation, then I would also ask if he has ever had the foundation inspected by a foundation repair company (who probably would not be an engineer). If so, who was it and what did they recommend? I would also ask if the seller if he has ever had any problems with the operation of any doors (sticking) or made cosmetic repairs to the sheetrock or brick cracks. Call the city Building Inspection Department and ask if there have been any building permits issued for foundation repairs. If so, get the documents.

Retain an engineer to inspect the foundation prior during the option period. The engineer should also take elevations as a part of his inspection.

Many times, if a foundation has been repaired, the foundation repair contractor will have retained an engineer to review and sign off on the repairs. This engineer is the engineer-of-record for the foundation repairs. It may be possible to get this engineer involved in the inspection of the current condition of the foundation. If so, he should issue a written report of his findings.

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Posted by on December 29, 2014 in foundation repair


Building a Home on a Hill

Over the years, I have inspected numerous foundations of homes that are constructed on severe topography, i.e., where the ground surface slopes significantly, such as on the side of a hill or on a creek lot. Generally speaking, what I find is that portion of the foundation that is downhill, has settled. This settlement occurred because the builder/developer brought in fill material to level the lot prior to installing the foundation and the fill dirt consolidated (compressed) over time and allowed the slab to settle. Also, dirt located uphill will tend to move downhill (because of gravity). This action is called “soil creep”.” Soil creep” is a slow gradual action that usually occurs over a several year period.

Obviously, it is possible to design/construct a stable foundation for these types of conditions, however, the design needs to be well thought out. It is recommended that a site specific soil report be obtained that determines the soil properties & characteristics. The design engineer will then use the soil data to design the foundation. Many times, a foundation located on the side of a hill should include piers that are founded in a stable bearing stratum.

Usually, these piers are drilled concrete piers, preferably installed into a stable rock formation or if rock is too far down, the pier shaft is belled at the bottom to a diameter of 2.5 to 3 times the diameter of the pier shaft. In other words, if a 12″ diameter pier shaft is specified, the bell diameter will be 30″ to 36″ diameter (depending on what the design engineer determines).

Yes, this is expensive, but it is usually not as expensive as trying to install piers after the home is built and the foundation moves.

Also, when a home is being constructed on a severe hill, it is many times, advisable to install a retaining wall. I have seen many homes where the soil is moving downhill and causing a void space to appear under the slab. The only way to stop this “soil creep” downhill is to have a stable retaining wall stopping the soil. The foundation design engineer can determine if a retaining wall is necessary.

The object of this blog is to caution folks who are going to build a slab foundation on the side of a hill to be cautious AND obtain the proper engineering advice.

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Posted by on November 16, 2014 in foundation repair


Buyers Beware – Part 2

I once inspected a slab foundation of a residence for a lady who had owned a home for 15 years and was in the process of selling it. The home was about 2 years old when she purchased it from the original owner. It is located in a suburb of Dallas well known for having highly expansive clay soils. (This means that when the clays experience an increase in moisture content, they can expand significantly.)

She told me that she had a contract on the house but the buyer backed out after his general inspection reported that foundation movement had occurred. She did not understand why the inspector would come to that conclusion since, in 15 years, she had not had any sheetrock cracks, brick cracks (except for one minor crack) nor experienced any problem with any of the doors.

My investigation showed that the foundation was over 6” out of level and I concluded that the back of the foundation had heaved upward because of soil expansion. Furthermore, all of this occurred prior to her buying the home.

I suspect that the original owner knew about the problem and made cosmetic repairs and dumped the property. Unfortunately, when she bought the home (15 year ago), her general inspector did not warn her about the condition of the foundation.

The good news was that there had not been any significant foundation movement since she purchased the house; the bad news was that prior to her purchasing the home, it had heaved upwards and was 6” out of level.

If a problem with a foundation is defined as it being significantly out of level because of upheaval, then the logical remedy would be to lower the heaved portion. This can be done, but it is outrageously expensive and is therefore done infrequently. Because of the expense, this was not an option for her.

However, if a foundation problem is defined as having recent foundation instability, then she was in good shape because the home had not moved noticeably for 15 years. However, the big problem was that the foundation was over 6” out of level.

There was no financially reasonable remedy for solving her foundation problem. So, because the seller had covered up defects and she was not properly advised when she purchased the home, she was stuck with a nice home in a nice neighborhood that she could not sell at the going market value.

In a defense of her general inspector, the original seller of this home had the cosmetic damages repaired prior to putting the home on the market. If a seller of a home hires a professional painter and brick mason, they can make most defects in the sheetrock and brick disappear. And if a general inspector does not see cosmetic defects normally associated with foundation movement, they (at least some of them) assume that the foundation is ok.

So, could this have been prevented? Yes. The key is to either hire a very detailed general inspector who can look beyond the obvious (and possibly a structural engineer that will take slab elevations).

When she purchased the home, her general inspector (and her realtor) should have noticed the slab diselevation (I do not know how they missed noticing that the master bath was over 2” out of level). Nor did they notice that the kitchen base cabinets, the hall bathtub, the fireplace hearth and the fireplace mantle were all noticeably out of level.

To repeat, a buyer’s first line of defense against buying a house with a damaged foundation is to hire a competent, detailed-oriented general inspector. If there are indications of unusual foundation movement, he may recommend hiring an engineer to do a more detailed inspection of the foundation.

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Posted by on October 1, 2014 in foundation repair