Your Home – What’s Underneath It All

In South Texas, there are two kinds of homes:  Those with foundation problems and those that will have foundation problems.    Why is that?  It is a combination of costs, soils and lack of care of your foundation.  The vast majority of us are busy enough that we assume that the foundation of our home is something that needs no maintenance.  You don’t need to paint it or replace it like the roof on your home.   So it’s pretty much out of sight, out of mind.

Let’s talk a bit about what a foundation does and some of the ways it’s made.  The foundation is the support structure under your home.     In older homes,  a pier and beam foundation is utilized.  The pier and beam foundation is literally an array of piers made of cedar posts or concrete posts buried in the ground or bricks set on concrete footings.  A series of beams span the piers to support walls and the frame work of the home.   In colder climates where the ground freezes frequently, a concrete perimeter foundation is used often in conjunction with a basement.   In a perimeter foundation, beams span the perimeter and the house is built on the beams.  Currently, foundations in South Texas consist of a poured concrete slab.   The concrete slab is reinforced with steel bars called “rebar” or with tightly-stretched steel cables or even a combination of the two.   The steel cable version is called a “post tension” foundation.

 

 

Perimeter or T Foundation

 

Slab Foundation

 

Rebar and wire

 

 

If you are building a home, you might be able to choose the style of foundation on which your home would be built.  Since you cannot change the type of foundation you already have, you need to know the advantages and disadvantages you are faced with, as well as how to take care of your foundation.  The number one enemy of foundations anywhere and of any type is:  Water.  In South Texas, the general makeup of the soil is clay.  Clay soil swells and gets “gluey” when wet.  Soft, mushy soil wouldn’t seem like the best choice on which to build.  When dry, clay soil shrinks and becomes cracked.    It is not uncommon for many other soils to behave similarly to clay soil when wet or dry.   Because of this, the slab foundation has become the foundation of choice.  More on that as you read.

A pier and beam foundation is less affected by the movement of the soil because of the limited contact with the soil.  When the pier and beam foundation is affected by this movement, a foundation company can send a worker to crawl under the home and add  or remove shims between the piers and beams to level the home again in compensation for the movement.  A damaged or rotted pier can be replaced relatively easily, too.  Standing water will have a greater effect and undermine the piers more rapidly over time.   If the foundation area is not well ventilated, mold and other problems can develop.  Termites can build tunnels up the piers and get into the wood of the house.  It’s not that easy to make corrections with perimeter and slab foundations.

Since the perimeter foundation is almost never used in South Texas, I won’t cover its advantages and disadvantages here in depth.  Basically, these types of foundations are affected less by soil movement than from frozen soils.  They are problematic in areas where the water table is high.  The walls  can sweat, making it difficult to have a dry basement.  High water tables are not much of a problem in Texas, save for the coastal areas.  Frozen soils in Texas are not much of a problem either, as long term sub-zero temperatures are not a frequent occurrence.

The slab foundation has a number of advantages.  It can be poured on level ground or forms can be set up in such a way that slab foundations can be poured on the side of a hill.  Before slab foundations are poured, a groove is dug around the perimeter for the footing.  Then, the fill is arranged in such a way that “beams” are formed in the fill material.  If you could flip the cured foundation over, it would appear much like the inside of an egg carton with dividers between the hollowed areas.  In those beams, reinforcing bars and wire or steel cables are used to help strengthen the  concrete.   Pulling the cables tight after the concrete has set will further strengthen the slab.  This is called active reinforcement.    Here is a short video of the cables being pulled tight.  http://youtu.be/rNJGaiGYzAc?t=7s      When the cable is tightened, there is roughly 16 tons of clamping force.  Re-bar is passive reinforcement, and only adds strength when the concrete is put under a stressful load.

 

 

Post Tension Cable sticking out of the slab after it was tightened.

 

 

The slab is designed to “float” on the soil.  This makes the slab less susceptible to cracking by the soil expanding and contracting.   The solid construction has fewer openings for water and termites to penetrate.  Vapor barriers put down before the concrete is poured limit the amount of water penetration from the soil below.  Vibrators are used in the perimeter and dividers to remove air bubbles before the concrete sets, making a denser and stronger concrete.  Even the concrete itself can be tailored with additives that make the concrete stronger and more resistant to water damage.  With all that, you might wonder why there would ever be foundation problems.

Many things contribute to foundation problems.   Initial cost is the biggest factor.  Builders often only take a few soil tests in a given subdivision.   Soil tests are expensive and would add thousands to the cost of each house.  Using overly large amounts of concrete and reinforcing steel also can become cost prohibitive.   If your home happened to be built over one of these test sites, it probably will have the correct combination of concrete and steel in the foundation that would be nearly problem-free.   If your home was built over a softer area, your home will be more prone to issues.  What can cause issues with your foundation?   Rarely, cables are not tight enough, an insufficient amount of re-bar was used or the concrete was not cured correctly.  If any those things were the case, the foundation may have a greater tendency to crack or shift.   The biggest cause of foundation issues is water.  Imagine flexing a piece of metal back and forth until it breaks;  the foundation is exposed to the same type of force over time when the clay expands while wet and then contracts again when dry.

You can take steps to limit the extreme swings in moisture levels.  Other development around your home may expose it to more water.  Take a look at your yard.  It needs to slope away from the house in some direction.  If you find the landscape places your home in an area where water collects or drains away slowly, you should take steps to provide a way for the water to drain away more quickly or be diverted around your home.   Low spots should be filled or graded to move water away from the foundation.   Gutters should be utilized to direct the flow of rain water away from the foundation of your home.   Dripping hose bibs should be replaced before too much water collects in one spot.  Another source of water is the condensation drain for the air conditioning (HVAC) in your home.  You should add an extension to the drain pipe to move the water away from the foundation.  You don’t have to glue the extension to the drain pipe, you can just slip it over the drain pipe and then remove it to mow or trim the yard.  Reinstall it afterwards.   During extreme dry periods, use a soaker hose around the foundation and let it drip for about 6 hours once a week.

Should you be unlucky enough to start experiencing large cracks in the concrete or drywall in your home, it would be a good time to get in touch with an engineer that specializes in foundation repair.  If you wait until doors no longer operate properly, or large diagonal cracks form at the corners of doors or windows, the damage will be harder to correct and a lot more expensive to repair.  Don’t confuse small hairline cracks that follow a straight line with foundation issues.  They are probably caused by small settlements in the foundation or even the studs inside of the wall becoming drier.

Here is a short list of things to look for:

1.  Uneven or sloping floors

2. Cracks in exterior walls and bricks

3.  Displaced or cracked mouldings

4.  Cracks in floor, floor tiles or foundation

5.  Doors and windows do not operate properly

6.  Separation of doors, windows and garage doors

7.  Spaces between wall and ceilings or floors

8.  Walls separating from house

    Here are some pictures of damage:

Concrete floor damage in garage.

 

Diagonal crack in drywall.

 

Exterior crack in brickwork.

 

While these are extreme examples, you see some typical places where these problems can develop.

 

If you have found these signs, it’s time to call that foundation engineer.  Even though I am not an engineer, I have seen examples of repairs that have not been done correctly/completely when I have been hired to repair damaged sheet rock.  For example, if one corner of your home is settling, the usual fix is to dig down to a more solid area and install piers or steel beams to support the area after it has been leveled.  While that will keep that corner in place, your foundation can no longer float as it was designed to do.  In most cases, the proper repair would be to install piers under all areas of the foundation so that the slab can be supported completely.   It is a costly repair.  Once cracks form in the foundation, termites can enter and pipes in the slab may be damaged allowing water to be trapped under the slab.   So, after the foundation repairs, you should keep an eye open for insect damage too.

By following those few steps to manage water around your foundation, your home can stay in the “will have problems later” column and out of “have problems now.”

Thanks for reading.  Please visit my sponsors.  If you have questions, please e-mail me using the form on the “Contact Me” page.  I’d be happy to try and answer them for you.  If you need a handy man in San Antonio, please call or text me @ 210-452-5816

MrFixItMike!

 

 

 

One Response to Your Home – What’s Underneath It All

  1. thanks for share!