When shopping for a new home, it&#;s easy to get caught up in the bright and shiny features and add-ons before anything else. New homebuyers should take the time to consider the less exciting (but equally important!) structural elements of their investment. The strong bones of the house will determine its long-term value. A home with stability and longevity will save money in the long run on repairs and play a part in generations of happy memories to follow.
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To increase stability and overall lifespan, a post-tension foundation is an ideal option for single-family homes. It not only functions as a safeguard against cracking in highly-unpredictable soil conditions and wet climates, but it also adds to the home&#;s value.
Because of its unparalleled versatility, a post-tension foundation is compatible with any home type from a sprawling ranch layout to a two-story estate. This type of foundation also uses less steel, which reduces costs. While there are minor drawbacks, the post-tension foundation provides critical support and high-quality structural benefits that any homeowner can enjoy.
What Is A Post-Tension Foundation?
Simply put, a post-tension foundation is a specific type of slab-on-grade foundation. The concrete is reinforced with threaded steel cables that are tensioned after the concrete cures. To allow the cables to slide more easily after the concrete hardens, the steel is encased in plastic sheathing to prevent the cables (tendons) from touching the hardened concrete.
The plastic sheathing is stretched post-pour, which tightens the slab and applies intense force to the concrete system to create a heavily-compressed state. A slab without reinforcement holds a very low tensile strength and is prone to cracking as the soil shifts. However, in a highly compressed state, a post-tension foundation can reduce the potential for breakage.
Post-tension foundations are often compared to standard rebar foundations in which a grid of strong steel is set in the poured slab for reinforcement. There are benefits and costs to both options, but the differentiator is how the rebar is tightened.
Benefits
When considering a post-tension foundation, you will want to consider the qualifies that make it an excellent choice for any new home.
Post-tension foundations are extremely versatile and may be the ideal solution for environments that do not support other types of home builds. Particularly in the Gulf Coast region and tropical areas with largely expansive soils that have a tendency to shift periodically, a post-tension foundation operates as a stiff apparatus to resist cracking. Similar to a boat that rocks back and forth on the waves as one large fixture, the foundation will ride the soil movements as it shrinks and expands with moisture changes.
Compared to the intricate arrangement of rebar that must be laid with precision for a standard conventional slab, the post-tension cables are easier to install. Experts will need to use specific machinery to tighten the cables once the slab hardens.
There are two major benefits to using less steel in the home&#;s foundation. The first one is the structure becomes more lightweight than a conventional rebar foundation; it is also easier for the construction team to pour the concrete due to its placement and extra space for the cables.
Second, there&#;s an economic benefit. In general, a homeowner can expect to spend about $4.50 to $5.00 per square foot on either a post-tension or conventional rebar foundation. However, the total expense relies heavily on steel&#;s current market price. Steel is an expensive material, which translates into savings for the homebuyer.
Fewer cables embedded in the slab than an intricate rebar grid means a simpler and straightforward inspection. Problems can be identified easily and quickly and be repaired before they become significant.
New homes with a post-tension foundation are highly regarded as having inherent strength and structural integrity. Any builder can vouch for the importance of improving the home&#;s stability and longevity with the installation of a post-tension foundation. When it comes time for resale, knowledgeable buyers will recognize the home&#;s long-term value and be willing to pay more for this important structural feature.
Challenges
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While there are many wonderful benefits to consider, there are a few minor challenges to keep in mind when choosing a post-tension foundation.
When the foundation is initially poured, there is a vulnerable stage that occurs briefly in which the slab can experience minor cracking at the surface. Prior to tension and after about a week or so of curing, the slab becomes a thick chunk of concrete without tensioned cables to support the bulk of its weight. As a result, the longer ends may sink and allow the middle to buckle. Long, tiny cracks or webs will appear on the surface but do not cause an issue structurally. They may be an aesthetic issue in areas that remain uncovered by tile or wood surface coverings, such as garage flooring.
When post-tension slabs are set, the builder will often include a stamp that warns the homeowner against cutting or drilling into the foundation. Cutting into this type of foundation can be particularly risky for even the most highly-trained construction expert due to the high level of tension suspended in the concrete. If a jackhammer accidentally strikes a cable, it may cause irreparable damage to the home, cause serious injury, and even death.
As previously stated, cutting into post-tension slab foundations can be particularly dangerous and should be avoided. When the bars rip through the slab, they become nearly impossible to repair. Homebuyers should consider any future plans for remodeling, which may prove to be a challenge if it involves adjustments to the foundation.
Phenomenal Foundation Fit
When considering options for building a dream house from scratch, homebuyers should consider the fantastic benefits of a post-tension foundation. Its structural integrity, economic pros, and overall quality makes this a great option in any climate for any home.
Melanie Theriault is a writer, counselor, and lifelong learner. She holds a B.A. in Sociology from Southwestern University, where she discovered her passion for fostering human connection through storytelling.
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Jon, I dont like the idea of covering an entire slab with antifracture membranes. Maybe I should have thought about that before i typed greenskin. I spent a lot of time talking to a tech sup. guy from merekrete once and he brought up the point that vapor and moisture coming up through the slab can cause a membrane that tries to block it to come debonded.On the job I'd called on, I used merecrete fracture gaurd over the whole floor but left a 6" strip of bare concrete around all walls, interior and exterior because thats what he told me to do.
Doesnt ditra allow vapor and moisture to escape, as well as provide better protection from vertical movement? I think That would be the way to go. I think you would still want to place movement and perimiter joints.
LT, If a whole floor antifracture or uncoupling membrane isnt in the cards on this one, and you cant talk to a gobis type inbetween now and the time you need to start tiling (guessing tommorow?) Id say just make sure to cross your t's and dot your i's, or in our world- perfect coverage, expansion joints, perimeter joints, the redgaurd etc.
I might be you could voice your concern to the GC, and possible get him to sign something saying that you'll only warranty damage caused by horizontal movement that isnt excessive, and only on cracks existing at time of install. Which would probalbly require some sort of statement that he's inspected the slab and all cracks were dealt with. that way, if a crack develops elswhere youve got proof it wasn't there at the time of install.
Maybe you'll be comforted the know that Ive seen LOTS of intallations over post tension slabs in which the whole house is tiled, no expansion joints, no perimeter joints, everything just cut up and grouted to the baseboard and they've all seemed fine, for now.
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Hank
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