To See Part 2 Of This 2-Part Article Click Here: Slab Watering Part 2


This Is Part 1 Of A 2-Part Article Is About Slab Watering.  It’s provided as a public service by Al’s Plumbing, Heating & A/C in Plano, Texas.  Al’s provides repairs and replacements for every plumbing component in your home.  Al’s repairs slab leaks.  We also provide under-slab water pipe & sewer line repairs and replacements.

Al’s Plumbing, Heating & A/C provides repairs of all brands of Central A/C, Gas or Electric Furnaces, & Heat Pumps.  Al’s sells and installs new HVAC systems from American Standard (made by the same company as Trane), Ameristar (made by same company as American Standard), and Coleman HVAC (made by the same company as York HVAC).

Call Al’s today to discuss any concerns or problems you are having.  We can arrange an appointment at your convenience.

This article goes into notable detail as to why slab foundations become damaged.  The same slab movement that damages foundations is also responsible for slab leaks.  We describe how to set up an Automated Slab Watering System for your home with a modest investment of time and money.  With this system operating correctly, the soil moisture-level under your home will stay much more consistent around the edges. Moisture-level stays consistent nearer the slab’s center without interaction from you.  Slab Watering minimizes slab movement, slab leaks and slab damage.

If You Want Only The Information For Establishing An Automatic Slab Watering System, It Is Located At The End Of Part-2.

slab leak due to cracked pipe

A Slab Leak Is A Fractured Water Supply Pipe Caused By Slab Movement

Need To Know How To Detect An Active Slab Leak?

Click this link to go to our article:  AlsPlumbing.Com 17 Signs You Have A Slab Leak


Residents of DFW are not strangers to Slab Leaks.  Thousands of them are repaired in north Texas every year.   Did you know you can do something that reduces the risk of slab leaks and slab damage?  With both slab leaks and foundation damage being some of the most expensive repairs DFW home owners can be faced with, we will tell you how to reduce your risk.

A simple recurring house maintenance task is that is needed to help protect slab foundation’s in DFW.   It’s called SLAB WATERING.  Your home’s slab foundation is subject to movement due to the drying out and rewetting of the expansive soil under your home.   This movement does not occur uniformly, as much more happens at the edges than near the center of the slab.   This uneven movement is what can damage water-supply pipes and sewer lines under your home.  These pipes are attached to the slab from underneath.  They cannot endure recurring slab movement without becoming stressed and more prone to failure.

photo showing sewer lines hanging from slab foundationSHOWN: Sewer Lines Attached To The Underneath Side Of A Home’s Slab


photo of homes in foreground and dallas skyline in background

DFW Slab Foundations, Damage, & Repairs

+ How To Minimize Foundation Damage With Slab Watering

This article describes in detail how DFW’s expansive soil can damage slab foundations, and why.  Slab Watering information is at the end.  If you seek only the details how to create a slab watering program for your home, the last section is all you need.

For those who seeking details about foundation damage, you an learn how & why your slab became damaged.  Next you can learn about slab foundation repairs.  Repair information is unbiased, and does not include any “Ours Is The Best Repair Method” marketing verbiage you will find in many advertisements.  Als’ Plumbing, Heating & A/C does not do foundation repairs.  We do not provide recommendations for foundation-repair companies nor for any specific foundation repair method.

Also included are descriptions of the types of slab foundations DFW homes have.  This is largely based on when the home was built.  You can check your tax records for year of construction.  Knowing the year the house was built, you can see information regarding the most likely type of slab your home has.

NOTE: Some homes in DFW are built upon piers.  They are typically Pier & Beam.  This means the home was built with wood beams sitting upon piers, and has a crawl-space between the home and the ground.  If your home is Pier & Beam, you need not read further than the description of Expansive Soil.

NOTE: This article is written specifically for the Dallas & Ft. Worth, Texas metro area.    Some information presented here may be applicable to other areas that have expansive soils.  If you live outside the DFW area, your home’s slab foundation is likely built differently + your area’s soil is likely different.  If you live in the northern U.S. — slab foundations are built completely differently than in DFW.   This article of no value to those living in the northern U.S.

graphic showing location of expansive soils in texas

What Is Expansive-Soil? 

DFW’s Expansive soil has a lot of expansive-clay in your lawn + under your home’s slab foundation.  When the soil gets wet, it increases in volume (size).  When it gets dry, it decreases in volume.   The changing volume of expansive soil causes movement under your home’s slab, particularly around the edges.  The details are presented below.

photo of expansive clay soil wet and dry

Shown:  Wet Clay                 Dry Clay

photo of texas expansive soil when very dry

Shown: DFW Soil When It’s Extremely Dry

The photos above demonstrate how the volume of expansive soil decreases when it dries out.  When it gets wet, the volume increases once again.  Your home’s slab foundation is designed to “float” upon the soil.  The slab has some ability to accommodate soil movement.  If the soil’s moisture-content is allowed to vary tremendously, many slabs cannot accommodate that.  Over time, the slab will likely become damaged due to excess slab movement.  Slab leaks are another symptom of neglected Slab Watering.

The good news is that you can minimize slab movement with Slab Watering.  It keeps the moisture-content of the soil near the edges of your home more consistent.  The 3 feet of your lawn immediately surrounding your home is all you need to water for the slab’s benefit.  It is not required you water your entire lawn.  Also, watering-restrictions do not apply to slab-watering.  Note: There are typically certain hours when you cannot slab water, check your city’s website for details.

  • Engineer Ian Ray of Evergreen Structures in Dallas says “The most common cause of foundation problems in North Texas is due to the “very active clay soil running through North Texas”.
  • Jean-Louis Briaud,  President of the International Society of Soil Mechanics & Geotechnical Engineering says “What damages foundations is when the slab bends due to uneven soil moisture-content under & around the foundation.”

Eastern Texas Is Home To A Large Area Of Expansive Soil 

location of expansive soil in texas

This diagram shows were the highest frequency of expansive soil is located in Texas (red)


DFW Is Within An Area Of Texas Having One Of The Highest Concentration Of Expansive Soil 

  • The Dallas area is within the Blackland Prairie.  The soils here are comprised of three primary types (Austin Chalk, Ozan Marl, & Eagle Ford) often referred to as “cracking clays” due to the large deep cracks that appear during dry weather. The soil’s higher clay content makes it susceptible to significant expansion & contraction with changing moisture-content. 

map of soil types in texas

Soil Layers

soil layers diagram

SHOWN: A Photo & Description Of The Different Soil Layers

Regarding Slab Movement, the two soil layers of most interest are:

“B Horizon”  This layer is where expansive-clay is located.  In DFW this layer is quite thick.

“R Horizon”  This is the bedrock layer.  In DFW, it’s quite far down.


Click On This Link for a short YouTube Video further describing DFW soil:  YouTube DFW Expansive Soil (Produced By Dallas Ft Worth Foundation Repair)

* This is not an endorsement of Dallas Ft. Worth Foundation Repair only because we don’t have first-hand knowledge of them.


image with the words how weather affects your home's foundation

DFW RainFall By Month 2015-2017


Source: National Weather Service  National Weather Service Historical Monthly Rainfall for DFW

In 2017:

  • 3-1/2″ (inch) of rain fell in April.
  • Less than 3/4″ (inch) in May
  • 8-1/2″ in July
  • Just under 1/2″ fell in September
  • These numbers demonstrate how volatile monthly rainfall amounts are in DFW.
  • This is why slab watering is so important.  It ensures more consistent moisture-content in the soil immediately around your home.


Slab Watering & The Moisture “Active Zone” in DFW Soil

expansive soil active zone diagram

  • The American Society of Civil Engineers (ASCE) estimates that half of all homes in the U.S. are built on expansive soils.  Over time, half of them will experience some degree of damage to their foundation directly related to expansive soil.
  • In North Texas, there is a varying depth below the surface called the “Active Zone”.   This zone can be up to 15 feet deep.  Within the active zone, the volume (size) of the soils increases or decreases with changes in soil-moisture level.   Below the active zone, soil moisture-content changes very little (if any).   Due to stable moisture-content, there is no or only minimal expansion or contraction of the soil below the Active Zone.
  • Your home sits on top of the Active Zone of soil.  Slab watering is very important due to this active area of soil expanding and contracting with changes in soil-moisture.

How A Slab Foundation Becomes Damaged By Expansive Soil

slab crowning due to inadequate moisture at edges

Shown: The “Crowning Effect” Caused By Overly Dry Soil Along The Outside Edges Of The Slab

Moisture level stay fairly consistent near the center of the slab.  It changes a lot along the edges.   Because of this, the slab does not move uniformly.  Little movement occurs near the center.  Notable of up & down movement can occur along the slab’s outside edges when slab watering does not occur.    

  • When the soil is too dry, the slab drops around the edges, creating a “Crowning-Effect”
  • When the soil is too wet, the slab rises around the edges, creating a “Dishing-Effect”

diagram showing slab foundation dishing / cupping and doming / crowning

  • Floating Slab Foundations are not perfectly rigid.  As the underlying soils move, the slab is designed to move up & down with the soil.   Most common is when the edges of the slab bend downward (crowning) due to too little soil moisture & upward due due to too much soil moisture (dishing).

floating slab diagram


  • With a slab watering program in place, over time recurring slab movement often causes stress on the slab foundation, resulting in cracks in the slab.  Then, the damaged slab foundation can no longer adequately support the home.  This begins causing damage throughout the home.  Foundation-related damage occurs both inside & outside the home.
  • As the slab moves, the home moves with it.  The more rigid or brittle a building-material is, the sooner damage occurs, and to a greater extent.  Examples: brick veneer is more rigid than vinyl or wood siding.  Ceramic floor tiles are more brittle than vinyl tiles.

Over Time, The Foundation Can Become Damaged Due To Recurring Uneven Slab Movement

 graphic of two story home

Slab Movement & Settling Can Damage Many Home Components

We often think of the high cost to repair foundations.  What can become equally expensive is repairing the damage caused to the house due to slab damage.  The cost of slab watering for an entire year would not pay for 1 installed foundation pier.

crack in foundation as seen from outside the home large gap in slab foundation needing large repairs slab leak due to cracked pipe

Cracked Foundation                                     Cracked + Settled Foundation      Broken Water Pipes (slab leak)

cracks in exterior brick due to slab movement  damage to exterior brick due to slab foundation movement  brick exterior damage due to slab movement damage to exterior brick due to slab foundation movement

Damaged & Separating Brick   

unlevel window interior damage due to slab movement  damaged drywall due to slab foundation movement  exterior door out of level due to slab movement

Uneven Windows                                                                               Drywall Cracks                                                                                 Uneven Doors

 cracked floor tile  damaged ceramic tile due to slab foundation damage cracked floor tile

Damaged Hard-Surface Flooring Caused By Cracks In The Slab


  • GOOD!  Our Goal Is To Inspire You To Begin A Slab-Watering Program  It Will Help Stabilize Soil-Moisture Around The Edges Of Your Home.
  • Note: Al’s Plumbing & HVAC Does Not Do Foundation Repairs.  Al’s Does Not Recommend Foundation-Repair Companies.


graphic with words foundation repair

NOTE: This foundation repair information pertains only to DFW.

DFW Foundation Repair Provides Stable Foundation Support By Going

Below The Active Moisture Zone To Either Stable Soil Or Bedrock.

Concrete Piers

  • Pre-cast concrete cylinders (6” diameter X 10” long) are hydraulically pushed into the ground and stacked on top of each other.  The weight of the house keeps the piers in position.  In DFW concrete piers are typically driven 10-15’ into the ground.  In some DFW cities (such as Irving) piers may be installed as deep as 22’.

photo of concrete foundation repair piers

Concrete Foundation Repair Piers

photo of hydraulic machine to push concrete piers into the groundHydraulic Machine That Pushes Concrete Piers Into The Ground

concrete piers foundation repair

Concrete Piers Foundation Repair Reaching Stable Soil (below the Active Soil Zone).

  • Concrete Piers are typically driven to the “Point Of Refusal”.  This means they cannot be driven any deeper.
  • Typically the repair reaches stable soil (below the Active Soil Zone).  When this occurs, there will be minimal further foundation movement (if any).
  • On occasion, concrete piers do not reach stable soil (due to the Point Of Refusal).  If this occurs, there will be reduced foundation movement.
  • Without foundation piers, your home’s foundation is entirely subject to the expansive-soil it’s sitting on.  Slab watering reduces stress on the slab foundation caused by movement.   Only in rare instances are new homes built upon foundation piers.

 Steel Piers

  • If a foundation repair reaches bedrock, there will be no further foundation movement.  To accomplish this, steel foundation piers are typically installed.
  • Steel Piers reach far into the ground to the point of reaching bedrock.  In DFW they are typically installed between 20′ — 70′ deep.  Steel piers are more expensive than concrete.   They may be necessary if concrete piers cannot be pushed deep enough to reach stable soil.

picture of steel foundation repair piers

Steel Foundation Repair Piers

photo of hydraulic machine to push steel foundation repair piers into the ground

Hydraulic Machine To Push Steel Piers Into The Ground

foundation repair steel piers

SHOWN: Steel Piers Foundation Repair Reaching To Bedrock

Concrete or Steel Piers are the most common foundation repair methods in DFW.   There are some variations in how they are designed.  In order to be effective, piers must go deep enough to reach areas not affected by changes in soil-moisture.  In DFW that depth is typically 12 — 22 feet.

  • Both pier systems are typically driven to “Point Of Refusal’.  The “point of refusal” is described as “when concrete piers can’t be driven deeper” or “when the home’s weight cannot push the concrete pilings deeper”.
  • Concrete piers are typically driven until they reach compressed clay.   In some cases “refusal depth” starts at 6-10 feet, with a common maximum depth of 15 feet.
  • Steel piers are typically driven up until they reach solid bedrock.  They can be driven as deep as 75 feet.
  • Some contractors may perform a soil test to determine the depth to stable soil.

Stable Soil Support compared to DFW brick homes weight (including the slab foundation):

  • Stable soil will support up to 3-4 tons per square foot
  • Weight of DFW Brick Homes:
  • 1 story: 200 pounds per square foot
  • 2 story: 275 pounds per square foot
  • 3 story: 350 pounds per square foot


To See Part 2 Of This 2-Part Article Click Here: Slab Watering Part 2



Al’s Plumbing, Heating & A/C provides repairs and replacements for every plumbing component in your home.  Al’s repairs slab leaks.  We also provide under-slab water pipe & sewer line repairs and replacements.

Al’s Plumbing, Heating & A/C provides repairs of all brands of Central A/C, Gas or Electric Furnaces, & Heat Pumps.  Al’s sells and installs new HVAC systems from American Standard (made by the same company as Trane), Ameristar (made by same company as American Standard), and Coleman HVAC (made by the same company as York HVAC).

Call Al’s today to discuss any concerns or problems you are having.  We can arrange an appointment at your convenience.  Al’s also has Emergency 24/7 Service.