Tuesday, December 28, 2010

Pier & Beam versus Slab Foundation, Part 2

This is the second part in our multi-part series of posts, "Pier and Beam versus Slab Foundation." Be sure to read the first post in this series, if you haven't already.

In our last post, we discussed pier and beam foundations (sometimes called post and beam foundations), including what they were, and their pros and cons. In this post, we'll covered the basics of slab foundations.

The Basics

Slab foundations are usually the easiest (and thus the least expensive) foundations to build. The slab is a flat concrete pad poured directly on the ground. This takes minimal site preparation, very little formwork for the concrete, and less labor to build than a pier and beam foundation. Slab foundations work well on level sites in warmer climates (like what we have here in north Texas and southern Oklahama). Slab foundations can be problematic farther north because when the ground freezes during winter, this freezing may shift the slab. This may damage the structure sitting on the foundation, plumbing running through and under the foundation, and the foundation itself.

How Slab Foundations are Constructed

In most cases, the perimeter of the slab is about 2 feet deep. The interior of the slab can be as little as 4 or 6 inches thick. Below the slab sit a 4 to 6 inch layer of gravel. To keep moisture from the ground rising through the gravel to the slab, a 4-millimeter sheet of plastic is placed. Reinforcing bar (rebar) is laid out in a grid framework (supported a few inches above the plastic sheet) and the concrete is then poured over everything.

This type of foundation is commonly called a floating slab since it "floats" on the soil. What holds the foundation in place is the deeper layer of concrete around the perimeter of the foundation.

In places with common and severe winter freeze, the concrete along the perimeter extends below the frost line.

The Advantages and Disadvantages of a Slab Foundation

Slab foundations offer the following advantages:

  • Slab foundations usually take less time to construct.
  • Slab foundations require less prep work of the site.
  • Typically, slab foundations cost less, due to the two points above.
  • Since there is no crawlspace under the home, there's no risk of animals getting underneath the structure.
  • Since the slab sits on the ground, entries and exits to and from the structure are close the ground -- perhaps only a step or two. This is good news for those with disabilities or other restrictions that makes steps difficult to navigate.

On the other hand, there are a few drawbacks to slab foundations:

  • Since the plumbing and gas lines (if applicable) run directly through the concrete slab, it's more expensive to fix these problems below the home. Also, shifts in the foundation can break pipes (fresh water, sewer lines, and gas).
  • Once a foundation has failed, it can be more expensive to fix the foundation since piers have to be sunk below the home. (In contrast, a pier and beam already has piers, which may only need adjustment.)
  • Slab foundations cannot be used in homes where a basement will be built.
  • Slab foundations cannot be used in areas with significant or prolonged freezes. The seasonal upheaval and other shifts can destroy a slab foundation.
  • Concrete slabs can crack. These cracks can range from minor annoyances to major problems.

Concrete slabs can be a good choice for your home or business, but it has to be done right from the get-go, and only for the right type of conditions. If you have quesitons, feel free to contact us or shoot us a question.

Thursday, December 23, 2010

Pier & Beam versus Slab Foundation, Part 1

The two most common types of building foundations in north Texas and southern Oklahoma are pier & beam foundations and slab foundations (also known as "slab on grade" foundations). As a rule of thumb, most foundations for homes built during the 60's and before are pier and beam while those built later are slab foundations. So, why the change in foundation types, how exactly is each type of foundation constructed, and what are the pros and cons of each? We'll cover each question over the next several blog posts and, as always, you can ask us your questions about foundation construction, repair, and maintenance and we'll give you the answers.

Pier and Beam Foundations

Pier and beam foundations (sometimes called post and beam foundations) have a crawl space (typically at least 18 inches) between the home and the ground. The base of the building is uses a series of beams supported above the ground via piers. This type of foundation takes longer to construct than a slab foundation, but allows easier access to heating and plumbing utilities. (With a slab foundation, it may be necessary to break through the concrete slab foundation to service or repair plumbing and such.)

Since the piers separate the structure from the ground, the foundation is less susceptible (as compared to slab foundations) to damage from the ground shifting. When ground shifting occurs and the foundation needs adjusting, the piers are more easily adjusted than is a slab foundation.

The advantages of a pier and beam foundation are:

  • Provides easy access to service plumbing, electrical and other issues under the house.
  • In many cases, pier and beam foundation problems can be less expensive to fix than problems with slab foundations.
  • Some remodeling projects and home additions are more easily accomplished with pier and beam homes than with slab foundations.
  • Since the structure isn't resting directly on the ground and air is a natural insulator, the temperature within the structure may take less energy to maintain. That is, your home isn't sitting directly on the cold hard ground during the winter and, thus, your heating bills can be less.
  • Many people feel that floors supported by a pier and beam foundation have a bit more give and are therefore more comfortable. This is not to say the floor rebounds like a trampoline as you walk across it, but there is a difference according to many homeowners.

The disadvantages of a pier and beam foundation include the following:

  • Pier and beam foundations take longer to construct than slab foundations. This increases the cost of the home or other structure.
  • Floors supported by pier and beam foundations may creak and move.
  • Broken vent screens and insufficient other barriers may allow bugs and rodents to get under the structure.
  • Pier and beam foundations have to be vented properly to reduce moisture. Sufficiently high moisture levels can lead to mold, rotting wood, musty smells.

In our next post, we'll discuss slab foundations.

Get more information by visiting www.AceFoundation.com.

Thursday, December 16, 2010

Do Steel Piers Rust?

"Do steel piers rust?" That's not an uncommon question.

The short answer is "No."

Steel piers are galvanized, which prevents rust. When steel is galvanized, it is dipped in molten zinc, which forms a chemical bond to the steel. Galvanized steel products gain good protection against rust and failure when used above or below grade. You can tell when an item has been galvanized, due to its unique silver color.

Wikipedia has a pretty good, technical description of galvanization. You can read it here.

Get more information by visiting www.AceFoundation.com.

Thursday, December 9, 2010

A Great Soaker Hose Tip

In our last post, we discussed soaker hoses and regulating the moisture around and under your foundation. This time around, we have a tip for a problem many people have when using soaker hoses.

What do you do if, by the time you've connected all your soaker hoses together, there's not enough pressure at the end of the last hose?

The first thing you need to do is understand why this occurs. The pressure is dropping at the end of the hose because there's too much hose for the amount of pressure provided at the water spigot. By the time the water reaches the farthest lengths of the hose, the pressure has dropped so much that the water isn't forced out the tiny perforations in the soaker hose.

The next thing to do is to see if there are additional water spigots you can use. Instead of stringing all your soaker hoses from one spigot, split your soaker hoses among two or more. If you're afraid of using all your spigots for just soaker hoses, you can purchase multi-headed spigots that attach to the spigot coming out of the wall. That way, you can hook up the soaker hose and still have a connection free for other uses when you're not using the soaker hose.

If you can't use additional spigots, you can alternate traditional hoses with soaker hoses. Since a traditional hose doesn't lose water from the tiny perforations like a soaker hose does, then it maintains a higher pressure through its length. With a combination of soaker hoses and regular garden hoses, you can reach the farther parts of your foundation and still maintain adequate pressure. You may have to run two sets of alternating hoses (call them Line A and Line B). Make sure when setting the two lines that where Line A's soaker hose(s) alternate with Line B's soaker hoses. When it comes time to use the soaker hoses (about once or twice a week, depending on soil conditions), connect Line A and run for 30 or more minutes, then disconnect and run Line B for 30 or more minutes. In this way, you'll water the entire perimeter of the foundation, yet each hose is only responsible for half the task.

Get more information by visiting www.AceFoundation.com.

Thursday, December 2, 2010

Soaker Hoses, Revisited

With all the rain we had in September, you might think we're nuts to be talking about soaker hoses again, but there's a good reason.

Soaker hoses are one of the best tools in the homeowner's toolbox for regulating soil moisture. Now that we're approaching the end of summer, it's a good time to get outside and check your soaker hoses for proper placement and overall condition. Make sure the soaker hose is buried about three inches deep and about six inches from the edge of the foundation so that the soil is soaked evening.

Do not place the hose against the foundation. Water placed next to the foundation (say, provided by a soaker hose placed against the foundation) runs through the cracks and pools at the bottom of the grade beam. (The grade beam is the thick portion of the foundation that is under the exterior walls.) The accumulation of water at the base of a foundation over time can reduce the soil's capacity to bear a load. When the soil loses enough load bearing capacity, the foundation will sink and your house can be damaged!

While you're checking the soaker hoses' position, don't forget to check the condition of the hose. Soaker hoses are pretty simple things. If you find a leak, tape it using duct tape (or similar tape -- ask at your local hardware store for appropriate substitutes). If the soaker hose is cracked or leaking from one of the fixtures or connections, replace the hose. The few dollars you spend on a new hose is a whole lot let than you'll spend on foundation repair.

Do you have questions about soaker hoses and your foundation? Then ask us!  In fact, you can ask us anything about foundation construction, repair, and maintenance. We love questions, so ask away!

Get more information by visiting www.AceFoundation.com.