Post Tension Slab Basics

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[@johnrossi2516]

Being in waterproofing for over 20 years, I've seen them cut twice by accident, one blew a patio onto the beach another blew a 2 ft hole in the side of a 22 story building. They are no joke when cut accidentally. 30 k lbs of stress looks like a hand grenade going off.

[@YOUNGSTARz93]

Plumber for over 10, years, Did a remodel on a home with post tension rebar for a restroom. Had to re route drain pipe. One of my helpers hit a tension rebar and it looked like as if a grenade had blowed right in front of us. He wasn’t wearing safety googles either so had a lot of debris go into his eyes. The scariest thing that’s happened to us in a long time. Was definitely lucky as the concrete was almost all shipped and only a small portion was left before he hit it. To answer your question as how do they replace them. they get a drill take of the plates that hold the tension on one side and drill it out as they have grease inside the sleeve. Once removed they drill in the new one with a regular drill and then used the tension machine.

[@percyjen6490]

I recently purchased a new construction home in Central Valley California. My builder used post tension slab. Good to know the dangers of slab but happy we won’t have cracks. Great job Matt!👍🏾

[@Sdewebb]

You will see hydration cracks in garage and front porch and back porch if they're part of the foundation

[@Meheimer100]

*cable is in tension. Slab is in compression . I always enjoy your content. Thanks for the steady stream of videos.

[@duggydo]

Luke Misenheimer I like his content also. However, this was cringeworthy at how little he knows about this stuff. I hope he takes down the video.

[@sloflo1]

He was not incorrect…he said amount of tension but did not specify the concrete or cable. He may have been talking about the “amount of tension” in the cable which is accurate. Tension in the cable is easier to measure than effective compressive stress. In most case when applying a preload you actually measure elongation.

[@anthonysarillo3911]

On future work on the slab the cables can be located with x-ray or ultrasound contractors. I have done that in Chicago for a very reasonable costs.

[@bertzerker747]

Hmm, still would feel like an earthquake could rupture out of the slab at anytime, for me that is... 🙏

[@craigtalbot607]

This is actually a terrific slab for earthquakes because the house moves as one unit. Finding the cables isn’t ridiculously expensive, but working around them usually is! This slab has saved my house - and caused me great frustration and expense too. Absolutely pros AND cons!

[@johnsmith-wc8gs]

I recently added a laundry room to a spa that had several levels above aka condos. All concrete construction w/ pt slabs. Xrays only ran around $250 where I needed to core for dwv. Sure life is easier with nothing in the way but where's the fun in that?

[@maggie_codes]

Thank your for sharing this!

[@marcosmota1094]

@@bertzerker747 My exact thought when Matt said that they can snap and tear through.

[@ryanbailey6600]

It’s an excellent system in areas of expensive soils because the entire house moves like a ship on water versus the House buckling and cracking. Builders like this system in places like Arizona because site prep and site drainage are less costly.

[@hotpotatapie]

Hi, we have a two story house in Phoenix AZ. that sits on a PT slab, built in 2007 by Trend Homes. I think they are defunkt now, but this house is very solid foundation wise. However, I do pay for the Service Line warranty to cover incoming water and outgoing sewage lines. It's $14 a month, very affordable considering what a broken line would cost to repair.

[@MrTyrael159]

As mentioned below, the slab is in compression, cables in tension. Concrete has negligible tensile strength. Thanks for the visual!

[@gregshepherd2911]

The cable will break with about 41,000 pounds of force. The working load is usually 70 to 80 percent of the ultimate strength. So there is usually about 33,000 pounds of pull on each cable.

[@king_josh6414]

Hi Greg. The pull I have seen on most sites ranges from 3000psi to 7000psi. How does that come close to 33000 pounds? If you could explain. Thank you

[@larrytinnin3357]

You can repair the cables by adhering a thin layer of carbon fiber along the cable line, it’s pretty expensive even tho it doesn’t sounds so. Also, maybe people have hit cables, ends rust out when grease caps are left off and fail, it is not end of the world just a costly repair, typically the cable when damaged do not come ripping out of the slab to kill you.

[@justotorres8970]

They work great here in Texas. My next house I would like to have this system. Not to worried about remodeling. Really any breaking of concrete slab you will weaken the slab with or without post tension. I have had to do remodeling with post tension, just take your time and break around they are spaced out a little further so you have more room to reroute plumbing.

[@bertzerker747]

They're now commonly used on ground floor residential...🧐 Who would ever dream of remodeling a brand new house? You'd want your floor plans to be right. Solid rock foundation, I'd consider engineered piles to justify any added expense, go TheBuildShow!!! 👍😲

[@shawn1869]

New build less than 5 years, i already got a crack running the entire home into the garage.

[@redking12155]

Hi. I’ve been subscribed for a while. Love the channel and learned a lot. Thanks for doing this channel Show me good ideas for an efficient house in a couple years when me and my wife Build. What do you know about Straw Bale houses? And Correct me if I’m wrong. At 2:09 seconds. You said that the slab was under tension. Tensions is pulling apart. Slab is under compression correct ? the wires are under tension because they’re being stretched. So the wires are pulling to center. Compressing the slab trying to pull it to the center correct?

[@johnfitzpatrick2469]

Not to disagree with an engineer, but, out of interest in Australia, solid rock foundation would see a waffle edge beam slab design. Only heavy clay, raft slab with pillar holes spaced to a sable foundation.(Big saving in concrete).

[@i_like_soup_]

my boyfriend is actually a PT stressor!! love trying to learn more about his work haha

[@kompshi]

i love all of your videos........very informative and very helpful in doing things the right way.

[@HighClassStunts]

on our job- cardinal tower, there is bottom mat, then post tension cable, and top mat

[@Fapsahoyx]

I saw a guy remodeling his bathroom with a jackhammer and barely missed one of these tension cables. He then decided to put the toilet right above it 🤣

[@cyndimorelli83]

Can you add a home addition to an existing post tension slab home?

[@timothykeith1367]

A rocky site in Texas may be capable of digging out with an excavator. A basement can be practical when the site has a ravine or some feature which can be filled in, local regulations permitting. The costs of hauling away the fill material prevents many from using a basement.

[@thecriticalopz2318]

We add 7500 to 7800 psi when doing post tension, I work post stress and yes it's very dangerous, it sometimes blows up on us while we're adding the pressure and the repair is even more dangerous

[@turboflush]

Used even more on multi level condos/hotels. Been around for along time.. but very dangerous. Especially if you don't know about it

[@elmerramirez3840]

Thank you men for this video, help me a lot, im planning start build my first house, i living in south Louisiana, I think i will use post tension- what you recommend?

[@gillamachster]

Having a home built soon with a post tension slab. How much time between the slab pour and the framing is best practice? And will framing before the slab is tensioned harm anything?

[@tylerwheeler12345]

You can begin framing on the slab immediately, before cables are stressed. Cables should be stressed 7-10 days after slab is poured.

[@johnchung3949]

Is that on Bullard? I drove by it this morning and thought about the post-tension cables sticking out.

[@peterinbrat]

Any thoughts on the Miami Condo failure? Was it post tension slab?

[@jamesball6069]

The argument about remodel of a huge house like that reminds me of the way PCs used to be built. you would have a huge old case and that was so you could buy a new motherboard, video cards, RAM. But really, it was just easier to get another one and ditch the old slow one. The thing is that most people stay in homes such a short time that jacking a slab for a remodel should be someone else's problem.

[@LIBERTY0RDEATH]

I have been on high rise buildings working and someone roto hammers or jack hammers through one of these cables and it sounds like a bomb goes off. Almost always they x ray the buildings before any drilling but I agree I wouldn’t want it on my house.

[@adminadmin9997]

When blowout happens they detension cables around that area and chip away the concrete till the cable that failed is exposed. You can use a coupler to splice the cable that failed. Pour concrete and retension

[@Therealphantomzero]

Question for all you guys I'm watching a building being built and they have the cables hanging out and they're already building the structure on top of it but they haven't intentioned it how long do they have before they can tension the foundation cuz I thought that you would need to tension it first before building on top of it

[@melperkins4677]

How deep are the cables from top of slab? OK to anchor a safe into slab?

[@SF-fb6lv]

2:08 he meant "...because the slab's in COMPRESSION..." (from the TENSION in the tendons (cables)).

[@jeffreywolfe7371]

Good video. But an important point is that the post-tensioning causes COMPRESSION in the concrete. Not tension in the concrete. That's the whole point :)

[@jeffreywolfe7371]

Not to belabor this point, but it's absolutely critical man! The reason why a boatload of tension is jacked into the PT strands, is 100% to make sure the concrete remains in compression. The only tension in the foundation is in the PT strands, and that is in order to keep the concrete from experiencing any tension. I'm a nerd engineer. Your videos are great, but that is a point that should not be overlooked or mistaken.

[@jeffreywolfe7371]

An equal and opposite reaction. Jack 25 kips of tension into a sleeved steel PT tendon, and the reaction is 25 kips of compression spread out over a certain area of concrete, to make sure it doesn't crack.

[@arieskauhi]

Its a hand held machine that pulls the cable. If you ever break the cable your screwed.

[@adminadmin9997]

Well now days alot of PT jobs are over engineered to the point if you have one cable fail it wont matter you have X amount of extra cables in that area that it wouldnt effect the integrity of the slab. Now if you dont have extra cables in a certain area and it fails. You chip away the concrete and add the cable.

[@thomazsilva620]

We do PT everyday , we had cables snaps before and ussually isn't a big big deal because they are over engineering, where usually allow us to have some that are broken . Last job we did 4 story building, over 2000 yards of concrete each level. It really isn't a problem , but you gotta have an engineer look at it. I haven't seen on houses , I wouldn't do on houses I agree because you might want to change the lay out in the future but apartment buildings go for it.

[@andrerichardson6029]

Matt the concrete slab will be in compression not tension. The steel rod are tensioned and they apply compressive forces to the concrete.

[@OOpSjm]

That's what he said, but he just mixed terms up as he was talking along.

[@theeraphatsunthornwit6266]

Seem dangerous

[@mistervacation23]

About a 9 on the tension scale Rube.

[@craigtalbot607]

Make sure your drain lines are all glued securely!! Just found out our 40-year-old post tension slab is going to cost us an extra fortune to fix a drain line that has come disconnected at a “y” joint!!!! NOT happy!!!!! 70’s tract houses are NOT friendly to future buyers!

[@marcosmota1094]

Should have been properly pressure tested...

[@michael-xe7rz]

They are better suite to Commercial building where more money exist to make changes later. They exist in Track houses because they are faster and cheaper.

[@eduardalbeza6202]

thank you for this information sir, godbless

[@borys444]

So Basically u will only b seeing post tension in warmer climates of the country?

[@mtbdad2]

I’m building a new home with pt foundation. They just finished framing. I went by yesterday and for some reason they had a 4 ft square area of the concrete jacked out and there were 2 cables cut. No dead bodies laying around. Lol. I’m wondering why they had to jack that up. Plus, after searching the web I couldn’t find anything substantiating your claim that people can get hurt by cutting a pt cable.

[@hamiltoncooper3603]

Yes people can get injured/killed my PT Cables.

[@Jordan22220]

Absolutely people can and unfortunately do get hurt. Don't kid yourself otherwise

[@michaelcayton4168]

I’ve cut many cables to repair them. Never seen or experienced a cable killing anyone

[@paulbetka2966]

I certainly didn't mean it as an insult. I admire Both Erik & Matt. IF I was in the building Trade's. I'D W I S H E D I could be as good. Experienced as them two gentleman ✝️ 🛐🙏 👍 🇺🇸

[@CybekCusal]

Trespassing? 🤦🏻‍♂️🤣

[@bravewave2084]

Informative

[@kodi8039]

Great video! +1 Subscriber

[@Beasthornen]

Good stuff man

[@mohdzabiullah5928]

5000psi force or tension is applied by machine

[@FuzzyBearOriginal]

I do this in Ireland.

[@davidwooten3430]

I would use the rebar that is mixed directly in the concrete. Saves a lot of labor for not much more $$

[@wishfulstinking]

Wow

[@rollzolo]

Cut someone in half...ghost ship..why not use roll out wire to save cost. Heard too many problems with pt.

[@shahsmerdis]

more than likely after the first home owner. no one will ever know the type of foundation. so the person who comes to the remodel wont even know not to jack hammer =/

[@danpants8218]

They stamp the concrete in the garage floor. People who do major remodeling know ti6 look in garage first, but cables do get broken sometimes but it's fixable

[@fredericrike5974]

@@danpants8218 Can you expand on that fixable comment? I was called to what had previously been a home for a client, and been sold- I had done some sub floor work to rebuild a shower drain that would not stay clear. the new owner had wanted to do some remodel in the kitchen/utility area and his plumber found the cable in less than five minutes of work- he identified his problem, but only after breaking the cable running just beneath the edge of the kitchen island. I got called because they knew aI had done below the slab work, and they wanted me to explain how. I did and they were unhappy; the whole at risk development was on land that had been farm land for a hundred years previously and had an 18" rise and fall seasonally, so the engineers specified post tension. I had known this and when I decided to break the bath room floor , had scraped the parraging from the foundation edges nearest and relevant to the bath, I knew pretty close to where the cables were. I avoided the cables till I found them and used a small hammer drill to get enough space to work. That 12" x 36" hole took me across three post tension cables and I spent more than six hours to get access. the repair and refill only took a couple of hours after that. OK, long story short- the new plumber's boss called a foundation engineer; he said it "could not be repaired to meet the installed standard". Don't know what happened after that.

[@danpants8218]

This was in Phoenix AZ and there is a company out there that can take old cable out and put new 1 in, i believe that's how they do it. I only know that the cables are wrapped in some kinda plastic so cables can be pulled through again. Never got to see it done and really not sure how it's done but that's what my boss told me after I broke 1 in half and the city of surprise az said it could be done also

[@kt71]

So a tone of tension?

[@banereaper4539]

super ask did ya hit anything when anchoring....nope...always nope. maybe if the anchor bolts were in the right spot to begin with we wouldn't have to dodge cables in slab

[@Knealeriley]

What keeps the end posts from shifting over time

[@chrisrabalais8984]

In the calculations, there is a "long-term" strength calculation which takes into consideration shrinkage and creep (constant compressive stress causing the concrete micro-voids to close up) of the concrete slab. As for the tendons, they are run through a tube in the slab. The tendon ends have chucks placed on them and are wedge shaped and inset into the slab; these are then filled with a structural grout which prevents them from moving. Also the tension in the tendon keeps the chucks from backing out. As a side note, Matt incorrectly states that the concrete is in tension; the tension in the tendons/cables cause compression in the concrete. Concrete is much better in compression (compressive strength is typically 10x stronger than the tensile strength).

[@persistentwind]

@@chrisrabalais8984 it seems you have some experience with this. Is the Jack hammering - remodel concerns really an issue? I can see how cutting a cable is a concern but if its fiberglass fill I would think a metal detector would find those cables with no problem.

[@zteaxon7787]

@@chrisrabalais8984 Ty for this.

[@chrisrabalais8984]

@@persistentwind Absolutely it is a concern, only if you do not know the location of the tendons in the slab. If you know the location, you should be able to safely jackhammer out the trench. But I would strongly encourage someone to get a qualified structural engineer to make sure that the amount of concrete you are removing doesn't jeopardize the slab integrity, i.e. don't run a trench along the entire width of the slab, crossing all the tendons perpendicularly. And yes I do have experience, I am a structural engineer (working on completing my PhD in structural engineering) and have my PE license, as well as I have recently remodeled my own slab-on-grade house (albeit we didn't have PT cables, just normal rebar).

[@danpants8218]

@@chrisrabalais8984 not sure why Matt cares about remodeling later on, i mean you're talking years down the road and is not his house equals not his problem. I broke a cable once not knowing back then about pt cables. Nothing crazy happened like cable ripping through the concrete but there was a company in AZ that fixed this kind of thing. Think it cost under 2000

[@douglastullo1461]

overkill for a house

[@paulbetka2966]

KZbin competitor Texas barndominium Does that 😊

[@fredericrike5974]

Actually the follow on Erik did (Erik and Matt know each other pretty well, from building shows and such) was a piece on how the post tension just didn't work for him. Most of his problems weren't with the system, but with the way it is sold and packaged; when Erik decided to do one, he had to order the cables and they come pre cut, treated and ready to install in their engineered positions. Erik usually builds out side municipal districts, in the country, and the supplier could not give Erik a quick turn around- that delay set the job back a couple of weeks. The follow on by the engineering company that tensions the cables was delayed twice (IIRC) and further stopped progress on the site. Erik made the call- he didn't want that loss of time control to rule his jobs, and he seldom has a long enough time window between contract day and the day he must finish a slab to build on. I hope I have explained this well- Erik, if you are reading this, feel free to fix it and blame me!

[@MrGusinfla]

Soooo not needed in a normal house slab

[@lsellclumanetsolarenergyll5071]

I would love to see a setup with fiberglass rebar instead of steel.

[@edcurwick8383]

So these are not required on ALL slabs by Current Code???

[@seanm3226]

Correct.

[@OOpSjm]

It's done to reduce costs

[@edcurwick8383]

Ian Powell So let's understand something please? Is Post-Tension required by Code in place of Rebar? Or it is merely used in place of Rebar because it is less costly?

[@OOpSjm]

@@edcurwick8383 used in place of rebar because it's less expensive (time & material). It's use in residential slab construction is pretty simplistic compared to large engineering projects. ie bridges, highrises, etc

[@jasonnielnasset2161]

No rebar? You clearly don't know how a foundation design works. Why do you have a website?

[@seanm3226]

Matt, I believe you’re completely misusing the term “post”.

[@craigtalbot607]

I think it means tensioned “after” the pour.

[@loverlei79]

Umm... I'm no engineer I'll go the traditional rebar route.

[@adminadmin9997]

PT is the future

[@matthewrivera5484]

Matt bring the other full videos to KZbin

[@southbridgeforestHOA]

no one remodells a slab foundaiton anyways, lol.

[@brezzz0077]

Why would anyone remodel a house on a slab, it's way to expensive. Always build or buy a house with a crawlspace

[@duggydo]

Rip up through the concrete and kill someone? You REALLY don’t know much about this stuff Matt.

[@CraftWon]

I’ve always heard this. Did a quick google search and some sites have reported this has and can happen.

[@adminadmin9997]

It's called a blowout. Sends pieces of concrete flying everywhere like a grenade going off. Stressing cables is very dangerous. Seen cables snap and through the stressing equipment off a high rise

[@simonlovi2518]

So much misinformation in this video

[@ArthurDentZaphodBeeb]

Matt, this explanation is beyond amateurish ("big engine"??). Get a competent structural engineer to discuss the technical details, and pros and cons of post-tensioning.

[@fredericrike5974]

Matt, I have to agree. And you know some really good engineers, as a matter of fact, I think you have introduced one who works in your office. We will give you a do over for this one! The Dallas Plumber