Home building tips

[RadicalModerate]

There is a technical difference between a "French drain" and a surface water control system and it sounds like you need the latter. A question: is the area where the ponding is occurring higher or lower (in elevation) than the adjacent roadway?

[mobstam]

I'm not in position to build a house just yet (would like to in the next 5 years or so), but I would like to educate myself on the process as much as I can.

Could someone explain the to me difference between a traditional slab foundation and a post-tension slab foundation? What are the benefits/drawbacks of each?

[RadicalModerate]

Basically, a post-tensioned slab has less chance of cracking, to an unacceptable degree, due to the active clay soil we have around here. It is also a lot more expensive than a regular slab. The key thing is to have a thorough soil survey done prior to designing your foundation/floor. This costs money, too, but it is a very good investment to make on the front end of the building project that can save you boatloads of money and stress later.

[CuatrodeMayo]

Keep in mind that unlike a traditional slab, you can't cut up a post-tensioned slab to install plumbing when remodeling. Cutting through a cable and hurt and even kill people. Even drilling holes requires caution and ground-penetrating radar.

[RadicalModerate]

Keep in mind that unlike a traditional slab, you can't cut up a post-tensioned slab to install plumbing when remodeling. Cutting through a cable and hurt and even kill people. Even drilling holes requires caution and ground-penetrating radar.

Excellent point! Since foundation waterproofing measures have improved so much over the years, perhaps it's time to start building houses with basements and crawlspaces rather than slabs on grade. You could have a built-in storm shelter plus easier access to plumbing drains, etc. Of course that nasty old "initial cost" thing raises its ugly head again . . . And then there is what seems to be a callous disregard for the basics of effective drainage measures on the part of some developers and homebuilders. Please note that I said "some" =).

[Easy180]

There is a technical difference between a "French drain" and a surface water control system and it sounds like you need the latter. A question: is the area where the ponding is occurring higher or lower (in elevation) than the adjacent roadway?

I would say it is higher than the roadway out front as my driveway slopes down. I guess I just need to have something put in to get it out to the front of the house as it's not going anywhere right now.

[SoonerDave]

I think post-tensioned slabs are now part of the homebuilding code in some (?) parts of Texas.

Just for info's sake, a conventional/traditional slab is literally that - a simple concrete slab poured within what's called a stemwall. Traditional "monolithic pours" are often reinforced by various techniques such as a mesh material or wired rebar. But even the best traditional slab will almost invariably develop hairline cracks at the corners. That's because as the water evaporates from the concrete during the drying process, the slab shrinks away from the stemwall and, in effect, you have discrete "masses" of concrete trying to "shrink" away from each other - hence the cracking.

A post-tensioned slab is kind of a "next generation" version of a concrete foundation. The slab is strengthened rather drastically by the placement of dozens of steel cables that extend beyond the edges of the stemwall and then mechanically placed under extreme tension, then anchored in place. The concrete is then poured, bonds to the sleeving material of the tension cables, and then the cables themselves are filled with material that bonds the cables to the sleeving. This makes the slab incredibly strong, and resistant to shifts in underlying soil. The caveat is that care must be taken to ensure the cable ends are sealed/waterproofed, as any moisture into the cabling can cause long-term corrosion.

The downside is, as others have noted, that you can't just cut up a PT slab. Think of a garage door coil spring - cut that sucker and you'll see the energy release as that spring EXPLODES with a thunderous BANG. Same idea applies here - huge loads are applied to the cables that then puts the concrete under compression.

It is more expensive, as you might expect, but a lot of builders are moving toward it.

[Garin]

Basically, a post-tensioned slab has less chance of cracking, to an unacceptable degree, due to the active clay soil we have around here. It is also a lot more expensive than a regular slab. The key thing is to have a thorough soil survey done prior to designing your foundation/floor. This costs money, too, but it is a very good investment to make on the front end of the building project that can save you boatloads of money and stress later.

Post tension is actually cheaper, You typically see around here only production homes doing them, I have seen some very large custom homes that have used them though take Stoops new home it is on a post tension slab. Most guys are using them for the money savings.

[RadicalModerate]

I would say it is higher than the roadway out front as my driveway slopes down. I guess I just need to have something put in to get it out to the front of the house as it's not going anywhere right now.

What you might consider are some "collection boxes" located in the area of the ponding connected to tight lines allowing the water to move out to the curb where it should be in the first place. Some careful checking of the relative grades, some digging, and permits for the curb or sidewalk cuts/drilling for the pipes correctly directing the water will be required. You lawn will be temporarily disturbed by these activities but it will get over it.

Suggest to your water wasting neighbor that it would only be fair for him (or her or them) to share the cost.

[RadicalModerate]

Post tension is actually cheaper, You typically see around here only production homes doing them, I have seen some very large custom homes that have used them though take Stoops new home it is on a post tension slab. Most guys are using them for the money savings.

I would agree with you if the "money saving" is based on long term projections rather than immediate cost.
All of the "production homes" I ever had anything to do with seemed to involve "remesh" (worthless) rather than #3 rebar in the slab.
(btw: I wasn't the "foundation contractor/sub" at the time. I was only a fledgling framer. =)

[SoonerDave]

I would agree with you if the "money saving" is based on long term projections rather than immediate cost.
All of the "production homes" I ever had anything to do with seemed to involve "remesh" (worthless) rather than #3 rebar in the slab.
(btw: I wasn't the "foundation contractor/sub" at the time. I was only a fledgling framer. =)

Rad, all this talk about foundations and construction remind me of not that many years ago when I was **that close** to starting a path to ditch my current profession and go into homebuilding. Love the craft of construction and learning about how to build things better and better. Even had a builder friend who was ready to line me up with some of his subs had I pursued it. Then, the chicken feathers emerged, and the cubicle farm won...alas...

[CuatrodeMayo]

Concrete is guaranteed to do two things:
1) get hard
2) crack.

[SoonerDave]

I would agree with you if the "money saving" is based on long term projections rather than immediate cost.
All of the "production homes" I ever had anything to do with seemed to involve "remesh" (worthless) rather than #3 rebar in the slab.
(btw: I wasn't the "foundation contractor/sub" at the time. I was only a fledgling framer. =)

As I grew up fascinated by the process of construction, and then later to learn and educate myself as a consumer, it was a sobering lesson indeed to watch the construction process on more than a few homes and find that while some of the, shall we say, shadiest (well, maybe it would be better to say "most money saving ) construction tactics were employed on some of the most expensive homes around. It wasn't a perfectly inverse relationship, mind you, but it became apparent to me early on in my observations that some builders in some very nice areas also knew they were building for people who knew/cared very little for how the house was constructed, just how it looked when it was done.

I was very fortunate to have enlisted a builder oh-so-many years ago who minded not at all that I was on the construction sites for the two homes he built for me (one in '91, the other in '99) nearly every day. He appreciated that I had at least a somewhat better than average knowledge of home construction practices, and he generally shot very straight with me. He was a crusty, curmudgeonly, but good-natured ex military guy who wasn't a particularly high-profile builder, but hired good subs who did good work with, well, one exception I won't go into here. Sadly, he passed away not long after he finished that second house in '99...

[mobstam]

I think post-tensioned slabs are now part of the homebuilding code in some (?) parts of Texas.

Just for info's sake, a conventional/traditional slab is literally that - a simple concrete slab poured within what's called a stemwall. Traditional "monolithic pours" are often reinforced by various techniques such as a mesh material or wired rebar. But even the best traditional slab will almost invariably develop hairline cracks at the corners. That's because as the water evaporates from the concrete during the drying process, the slab shrinks away from the stemwall and, in effect, you have discrete "masses" of concrete trying to "shrink" away from each other - hence the cracking.

A post-tensioned slab is kind of a "next generation" version of a concrete foundation. The slab is strengthened rather drastically by the placement of dozens of steel cables that extend beyond the edges of the stemwall and then mechanically placed under extreme tension, then anchored in place. The concrete is then poured, bonds to the sleeving material of the tension cables, and then the cables themselves are filled with material that bonds the cables to the sleeving. This makes the slab incredibly strong, and resistant to shifts in underlying soil. The caveat is that care must be taken to ensure the cable ends are sealed/waterproofed, as any moisture into the cabling can cause long-term corrosion.

The downside is, as others have noted, that you can't just cut up a PT slab. Think of a garage door coil spring - cut that sucker and you'll see the energy release as that spring EXPLODES with a thunderous BANG. Same idea applies here - huge loads are applied to the cables that then puts the concrete under compression.

It is more expensive, as you might expect, but a lot of builders are moving toward it.

So when putting in a post-tension slab, do they use a stem wall also? In other words, do they dig down along the perimeter (as for a conventional slab), pour in the concrete and make a stem wall, and then run the cables through the slab when they pour that?

I have heard anecdotes of one particular company in the metro who advertises that they use post-tension slab foundations, but don't actually use the cables to strengthen the foundation and don't dig down while making the foundation, in essence just placing the slab of concrete straight onto the dirt. Of course, this is all hearsay, but was wondering if anyone else had heard something similar.

[Rajah]

I'm about to remodel my kitchen and I am looking for suggestions on places to get good appliances, countertops, and (tile) flooring at good prices in OKC. I've been to Home Depot and Lowe's but I'd like to check out other options. Thanks

[Easy180]

I'm about to remodel my kitchen and I am looking for suggestions on places to get good appliances, countertops, and (tile) flooring at good prices in OKC. I've been to Home Depot and Lowe's but I'd like to check out other options. Thanks

Try Metro Appliances & More on W Reno for appliances

[Garin]

I'm about to remodel my kitchen and I am looking for suggestions on places to get good appliances, countertops, and (tile) flooring at good prices in OKC. I've been to Home Depot and Lowe's but I'd like to check out other options. Thanks

x2 for Metro , visit floor trader for your flooring needs. Depending on the type of counter tops you're looking for there are several good places, what kind are you wanting?

[Garin]

So when putting in a post-tension slab, do they use a stem wall also? In other words, do they dig down along the perimeter (as for a conventional slab), pour in the concrete and make a stem wall, and then run the cables through the slab when they pour that?

I have heard anecdotes of one particular company in the metro who advertises that they use post-tension slab foundations, but don't actually use the cables to strengthen the foundation and don't dig down while making the foundation, in essence just placing the slab of concrete straight onto the dirt. Of course, this is all hearsay, but was wondering if anyone else had heard something similar.

Foundations « AA Designs

[CuatrodeMayo]

So when putting in a post-tension slab, do they use a stem wall also? In other words, do they dig down along the perimeter (as for a conventional slab), pour in the concrete and make a stem wall, and then run the cables through the slab when they pour that?

I have heard anecdotes of one particular company in the metro who advertises that they use post-tension slab foundations, but don't actually use the cables to strengthen the foundation and don't dig down while making the foundation, in essence just placing the slab of concrete straight onto the dirt. Of course, this is all hearsay, but was wondering if anyone else had heard something similar.

Building code requires foundations to extend below frost depth, so I doubt anybody is doing just a slab.

[SoonerDave]

So when putting in a post-tension slab, do they use a stem wall also? In other words, do they dig down along the perimeter (as for a conventional slab), pour in the concrete and make a stem wall, and then run the cables through the slab when they pour that?

I have heard anecdotes of one particular company in the metro who advertises that they use post-tension slab foundations, but don't actually use the cables to strengthen the foundation and don't dig down while making the foundation, in essence just placing the slab of concrete straight onto the dirt. Of course, this is all hearsay, but was wondering if anyone else had heard something similar.

A concrete slab typically involves (in a perfect world, at least) a barrier layer, perhaps a layer of gravel/sand, then rebar or other reinforcement.

Keep in mind there two ways to do stemwalls - one that is poured atop a dug or excavated footing, reinforced with rebar, and then filled with concrete; the other, and is where the stemwall forms are simply framed and poured on a graded lot, essentially a single concrete beam. ("Pier and grade-beam" was how builders always described it to me). The latter is cheaper and quicker, but the former IMHO is the superior choice of the two. I guess a "third" way is really just to trench the permeter of the site and pour a slightly thicker "wedge" of concrete at the perimeter to serve the purpose of a stemwall, without it actually being a separate, containing wall structure.

While I could see that you could use a stemwall with a post-tensioned slab, drilling holes for the cabling in the stemwall before the pour, a PT slab from what I've seen/understand generally doesn't have one - you frame up the forms, lay out the rebar, put down the cables, pour, start the cure, then tension.

The only thing I can say about PT slabs is that the type I've read about use the cables. If there's another variety or technology, I'm not familiar with it.

[BlackmoreRulz]

Keep in mind there two ways to do stemwalls - one that is poured atop a dug or excavated footing, reinforced with rebar, and then filled with concrete; the other, and is where the stemwall forms are simply framed and poured on a graded lot, essentially a single concrete beam. ("Pier and grade-beam" was how builders always described it to me). The latter is cheaper and quicker, but the former IMHO is the superior choice of the two. I guess a "third" way is really just to trench the permeter of the site and pour a slightly thicker "wedge" of concrete at the perimeter to serve the purpose of a stemwall, without it actually being a separate, containing wall structure.

While I could see that you could use a stemwall with a post-tensioned slab, drilling holes for the cabling in the stemwall before the pour, a PT slab from what I've seen/understand generally doesn't have one - you frame up the forms, lay out the rebar, put down the cables, pour, start the cure, then tension.

The only thing I can say about PT slabs is that the type I've read about use the cables. If there's another variety or technology, I'm not familiar with it.

Partially correct, a pier and grade system will have pier holes dug down at the corners and various load bearing spots then a stem wall poured on grade bridging the pier holes.

A traditional slab will be poured in a three step process, the footings will be dug and poured first usually 18"-24" below ground, then a stemwall, then the floor after plumbing is roughed in.

The post tension slabs are poured monolithically...ie the footing, stem, and slab are all poured at once after the plumbing and tension cables are installed. They then come back and tension the cables afterwards.

[Klop]

Building code requires foundations to extend below frost depth, so I doubt anybody is doing just a slab.

This is correct.

[Klop]

The only thing I can say about PT slabs is that the type I've read about use the cables. If there's another variety or technology, I'm not familiar with it.

Seeing more and more use of an "engineered" slab. This basically uses the same process and technique as the post-tension, except without the cables. A monolithic footing and floor are poured together. But instead of using the PT cables, rebar and wire mesh are used for reinforcing.

[RadicalModerate]

Concrete is guaranteed to do two things:
1) get hard
2) crack.

You sound like a man who not only knows what he is talking about, but also a man who understands reality.
Real reality . . . Not virtual reality.
(maybe an app can be invented to keep concrete from cracking =)

Back when I was personally involved in The Business of Construction I used to have a (free) subscription to a magazine called "Concrete Construction". There were ads in there for admixtures to the mix that were nearly mind-boggling. One of the simpler ones was that "adding fibers to the [mix] so you didn't even have to use up any precious (worthless) remesh" spiel. I ordered some concrete once--with this additive--to help the slab beyond the capabilities of the remesh that I used anyway--actually, not me, but the top-notch concrete pouring and finishing crew I hired. The customer freaked out a little about the "little hairs coming up out of the slab" . . . Plus, before that, I got to listen to the finishing crew bitch about how hard it was to get a nice finish on the surface. (and in English, not that other language . . . =)

[Klop]

It should be noted that the Post-tension slab assembly that has become so popular lately has some negatives as well as positives.

The negatives would be:
* Typically a 2 x 10 is used for the outside form board setting on top of the ground. Henceforth, your slab is only 9.5" off of the ground requiring special considerations for exterior grading. And, this requires a relatively flat building pad.
* The brick ledge is set to within 1.5" of top of the slab, so it is possible to have concrete edges showing. Although, dirt is usually brought up to cover this.
*As previously mentioned, no saw cutting or drilling should be done to slab once cables have been tightened. If you intend to install a storm shelter in the garage, make sure cables are not in place. Also, make sure the plumber hits his walls the first time.
*Typically, costs are $2000 higher, although some money is saved by the builder on brick and footer concrete costs. So it could be a wash, price wise.
*More times than not, the exterior wall footers are not as large as you would have on a typical footing and stem wall situation. Also, this footer is inside the exterior wall line. This usually is not a problem on a single story home, but could pose a problem for a taller, more intense load placed upon this exterior wall.

Positives:
*The post-tension concrete slab system is an outstanding system for holding the slab in place. Concrete does not react well with moving situations, aka tensile strength. The cables will actually allow the concrete to bend but not break. Considering our clay soils, and with the recent implementation of earthquakes into the equation, the cables do an outstanding job of holding the structure together.
*Some companies are offering a 10 yr warranty on the slabs, of course if they're still in business.
*Works well for the "production" builders as often times they build the same plan over and over, therefore reducing costs. But, still allows them the advertising potential of the post-tension slabs.

In summary, the post-tension slab is another technique of achieving a quality foundation and slab, although it is not the perfect fit for all situations. There are many factors involved in achieving a quality foundation and slab for the structure being built. Not one technique will fit all situations. Research and consult.