The Slab is Done!

My slab has been poured. It's done. It's really done! This is a huge weight off my shoulders, and a big milestone in the progress of the house.

After my last post about the day the post-tension cables were installed, it rained for a couple of days. My dad and I had to dig out some of the trenches around the front garage. They are deeper than the rest, and the rain had washed sand into these trenches, covering over the pilings. We cleaned them out so the tops of the pilings were exposed again. By doing this, we disturbed the termite barrier that the spray had created. So I called them out to re-spray these trenches. They did so without charging me.

Also during this week, we spent alot of time patching places in the plastic sheeting where they had cut big slits for pipes, drains, and other protrusions through. The large holes they left allowed rain to seep into the sand and wash out sections of some "islands" into the trenches. Also, having holes like this in the plastic would allow moisture to work its way up through the concrete over time. This could show itself as stains in a wood or vynyl floor, etc. So we added patches of plastic to make the barrier tight around the protrusions. It was long and tedious work.

I also made sure that the cables and highway wire were suspended just above the plastic layer wherever possible. In some cases, the plastic tees used to hold them up had either fallen over or sunken into the sand beneath. The idea is for the reinforcement to be sandwiched within the concrete and not lying at the bottom of it.

There was also the parish inspection. Before I could request the inspection, I had to bring in the survey that was done since the forms were up. It needed to be reviewed and accepted prior to a request for inspection. I brought in the survey on Wednesday (I think). They approved it on Thursday and the inspection happened on Friday.

You gotta love these inspectors... Now I'm completely new at this. I don't know all the ins and outs of the building & permitting process. And, I might add, the parish has not been forthcoming with lots of useful information to guide me. So when the inspector called me to meet him at the lot, I sped off with the copy of the plans I keep in my car. When I gave them to him, he said he needed the stamped copy. And he said it with a smirk or a smile that said, "what are you trying to pull here? You know I need the stamped copy." I explained that this is my first house and that I am contracting it for myself. I told him I'd run home and get it if he could wait. "But that's the thing: I can't wait," he said. I told him it would take less than 10 mins. He reluctantly agreed. He wouldn't accept the unstamped plans to work from while I was gone.

So I drove home with all due haste, grabbed the stamped copy and drove back in about 9 mins. After this, he seemed to be much cooler about things. He passed me, and gave me some pointers about making sure the tees were turned up so the steel would be in the concrete, etc. We talked for a few seconds and I think he started to realize that I was building this house for me and that I wanted it to be better than the code requires. He seemed to take his guard down a little after that.

Okay, so the inspection was on Friday and the pour wasn't scheduled until Tuesday. This was due to the weather forecast and also because no one could provide concrete until that day. There was more rain forecast over the weekend, and I was concerned that it would wash out the trenches again. But the rain really wasn't bad, and it didn't do any damage.

The Pour

Even up to the morning of the pour, I was making last-minute efforts. My dad and I added the pipes leading from outside into the drain boxes so that exterminators can squirt termite spray into them.

We installed these as the pump truck was setting up. The truck was pretty amazing. The boom could extend all the way to the back garage. It was something to see. And you can in one of the photos below!

When they started to pour, they began with the borders around the floating frames (the front garage, the back patio, the front porch, etc.). For the garage, they dumped some concrete inside and then used shovels to fill in the part of the ledge for the stud wall to be built on.

They would build up the concrete around the higher side of the border and flatten out a path maybe 2 feet wide. Then they began filling in around the sides by the brick ledges. They used a vibrator to make the concrete settle and fill in everywhere. (I'm anxious for them to remove the forms this week to see how good the brick ledges came out.) When they used the vibrator, you could feel it in the ground when you were standing within 20 feet.

After filling in the outside border, they filled in the rest of the trenches and the whole house slab. Some began working that slab while they poured into the rear garage. At different points during the hardening process, they would do different things, such as inserting the anchor bolts and metal straps at the corners.

They left the front garage floor until last. This was so that the pump truck's time could be used wisely. The truck was there for 5 hours, and then they cut it loose. For the front garage, they let the last cement truck back right up to it. This saved me an hour's time on the pump truck.

The pour itself lasted from 7:30 to 11:30. But the guys were there finishing it until around 5:30. There were different parts of the process. After flattening it with a board, they later used a big circular machine that looks like a floor buffer, but with metal blades that smooth over the concrete. They explained that they run this over it three times. By the time they're done, it's as smooth as glass. And it definitely is!

It rained on the couple of days after the pour. That was good for helping it cure well. Here are some pictures. Enjoy!

Post Tension Stuff Installed!

Whew! I'm glad this day is over. It was a success, but it was stressful. Because of the last-minute things I remembered the slab crew hadn't done last night, I worried that my one-sub-after-the-other schedule wasn't going to work out. I started the day by waiting at the lot for the slab crew. Neither the owner nor his son was with them. But the other guy who leads their workers was there. I asked him about the styrofoam in the rear garage and raising the level of dirt under the level parts of both garages. He seemed a little confused or annoyed (after all they were only coming to cut off the tall pilings), but they did the work.

The pest control sprayer hadn't gotten my message from the evening before where I said I'd need to push him back from 7:30 to 8:30. So he showed up at 7:30 along with the slab crew. He said he had to go off to another job across the lake and that he'd be back around noon or 1pm. It was forecast to rain alot later in the day, so I figured I'd have to postpone all the day's work until tomorrow.

Then I called the post-tension slab company. I had left them a voicemail yesterday evening telling them to push back from 9:00 to 10:00. The lady who answered today said she thought I had left that message two days ago. Their crew had already left Slidell to get down here for 9. I was told that if they called them back it would cost me more than if they got down here and waited idle for a while.

So I let them come, and I called the pest control people to try and get the sprayer guy back. They sent me another guy in his place. The owner, who I had left the message with the evening before, apologized that he hadn't gotten the message to his employee. He had been sick when I called.

So the schedule went like this:

• 7:30 - Slab crew arrived & started work. First termite sprayer leaves for other job.
• 9:10 - Post-tension crew arrived. Started laying out materials and marking where tendons would go.
• 9:50 - Second termite sprayer arrived & began spraying from back to front.
• 11:20 - Spraying completed. Poly layer being laid down from back to front. Plastic was down before any of the haevy rain started.
• 11:30 - 2:00 - Post-tension cables laid out, along with rebar cage in the bay window areas. Sporadic periods of heavy rain with breaks in between.
• 2:00 - Post-tension crew finished laying highway wire in the areas where I plan to have tile or wood floor. They left at this time.

The bottom line is that everything was installed today that I had hoped to install. There was heavy rain for a few hours after the work was done. I worried about the rain messing up the termite barrier that was sprayed in the trenches (where there is no plastic layer). An uncle of mine who has built lots of houses went out to look at everything afterward and said I was fine. The termite protection wasn't broken.

So I'm relieved that everything got done. Tomorrow, the slab crew should be coming in the afternoon to install the floating forms (forms inside the perimeter like the sunken utility room, and the ledges in the garages, etc. After that, I get the inspection. Then I'm ready to pour.

Here are some pictures of the house as of today:

Trenches Dug - Well on the Way to Being Ready to Pour!

I can't believe it's been almost a week since my last post. In that time, they've finished digging the trenches for the chain walls. Today, the slab crew was on-site installing the styrofoam blocks that make room for the brick ledge around the house.

They wrap the styrofoam in plastic wrap to make it easy to separate later from the dried concrete. He described it as regular plastic wrap and called it Saran Wrap. So I bought two rolls of that stuff, thinking that they just strung it along the back of the blocks. I found out today that there's actually larger rolls of this available from Home Depot that they use. Sorry, guys!

I met the slab contractor today to go over some final details of how the garage floors will be formed. There are places where the ground is level and other places where it is sloped, etc. I used Google's SketchUp software to draw what I wanted. He told me he likes dealing with someone who provides detail on what they want. I was glad to hear that.

We talked about being ready tomorrow for the pest control people to spray the soil. Then the post-tension people can come after and lay the poly (plastic) layer and install the post-tension cables. Hopefully, we can do all this before it rains.

BUT, I just thought of a couple of things while typing this that may ruin that plan: They didn't add styrofoam to the garage or fill in dirt where they needed to. These are all things that need to be done before the spraying! So I need to call them in the morning to see what's up with that.

Progress on Fat Tuesday

Three words of advice: inspect, inspect, inspect! After the plumber finished installing the drains and the underground copper last week, I walked the lot to make sure all the necessary lines were in place. I saw that there was no water line to the icemaker in the kitchen. I called him on Monday (yesterday) morning. They had just had the parish inspection. He thanked me for noticing that because they had completely forgotten about the icemaker. They installed that line, along with the utility room floor drain, that day.

With all the plumbing done, it's the slab crew's turn to come back and dig the footings (chain walls) down to the pilings.

Today, it's Mardi Gras here in southern Louisiana. Those festivities stopped being attractive to me long ago. But I was told that all the slab guys would have the day off. So I asked the slab guy to CALL ME when they would be out there again. He said he would. I went out this afternoon to do a little cleanup and organizing of wood stakes, etc. Lo and behold, the crew was there digging out the trenches with shovels! Hey, at least they're ahead of schedule. But I wish they'd let me know when they're going to be there.

If they dig these trenches and then it rains, the trenches will get filled in and they'll need to clear them again. But hopefully we won't have much rain, and they can finish them quickly. Then, I'll need to schedule the termite treatment of the soil and the installation of the poly layer & post tension cables (hopefully one right after the other).

Sand Spread Inside Slab Area

On Monday (Jan. 21), I had the sand delivered to fill in the space under the slab. It took 144 cubic yards and $1,800, but I should now have enough! I had the same bulldozer man that I used for filling in the whole lot and sand from the same company.

At first, the bulldozer wouldn't start. Probably because it was the coldest day so far this winter. I had asked him to be there for 7 AM. The sand didn't start coming until around 7:40, but he didn't get the dozer started until 8:00. By then, the first two loads were on-site. The sand didn't come as quick as I would like. I had to call and ask for a second truck to help. They sent the second truck twice, but afterward they went back to one truck. The last of the 12 loads was delivered at 12:40. The dozer guy still had some leveling work to do, and it took him until around 2 PM. After the last load of sand was spread, I had about 1/4 to 1/2 a load left over.

Also in the morning, the slab guys came out to move the rear garage form 4 inches closer to the front. They also removed a 2x12 from the back of the house so that the dump truck and dozer could get back there. All their work took about half an hour.

That afternoon, I went across the lake to see some Alenco windows from a place that gave me a quote. I'm reconsidering vinyl windows. For some reason, I had convinced myself that they wouldn't be good enough to satisfy me, and that I really wanted fiberglass frames instead because of their sturdiness and thermal insulation qualities. The only place I've found that has fiberglass is Pella, and their prices are way high. I'll continue to look for other suppliers of fiberglass windows, but I'm comfortable with the vinyl after getting a good look at them.

On Tuesday, I let the surveyor know that I'm ready for them to survey with the slab forms in place. The ETA is sometime late this week. I also called the plumber to let him know I'm ready for him to start. He said it would be a few days before he could begin. I asked him to call me and let me know when he'd be out there.

Slab Form Progress, Planning for Fill Dirt

After getting most of the form up on Monday, I called the slab contractor on Tuesday to let him know the rear garage was too far back and there wasn't the required 3ft setback from the property line. He wanted me to get the form surveyed (which I have to do anyway) in order to tell for sure. Well, I already have a survey that tells me where the property line is. If they come out to survey the form once, it's included in my builder's package. If the form is off and they need to fix it and have it surveyed again, it's going to cost me extra.

In the meantime, the slab guys came out again sometime either Tuesday or Wednesday (it rained all day Wednesday) to put more of the bottom layer of 2x12s on the house. I saw this when I visited the lot with my parents around 2PM on Thursday. It must have been right after we left that the slab crew had more wood delivered and came back out to put the bottom 2x12s on the garage. I didn't know they were coming.

That evening, I called the slab contractor and left him a voicemail about the garage again. I wanted to tell him that he needed to fix the garage before I got another survey. He never called me back, and he didn't answer his phone on Friday morning. So I called his son. He still didn't tell me they had been working the day before. I told him about the garage and asked him when they could meet me at the lot to talk about it. He said it would be the day after (Saturday).

Later on Friday, I called to order the 125 cu yds or so of sand that I'll need to fill in under the slab. When I went to meet the first dump truck at the lot, I saw that they had completed the garage form. I wish they hadn't put more work into something I already told them needed to be changed!

As for the sand, the driver said the ground was too soft inside the slab form to back all the way up inside for dumping. And there's one piling sticking too far up that would cause trouble as well. So I had to make arrangements for a bullodozer to be on-site on Monday morning. They'll dump the sand just inside the form, and the dozer will spread it from there. I need about 10 loads of sand. It's been raining all day today, so I hope the dump trucks are able to back up as far as they need to on Monday.

Finally, I called the slab contractor on Friday sometime after I talked to his son. He said he was on the lot looking at it! Why don't they call me to meet them there? Anyway, I drove over right away. I showed them the copy of the survey (which they already had) and he could see the garage needed to be moved. He claimed they had worked solely from the plot plan of my drawings. They started measuring from the street as they formed their way back. And it wound up that this placed the garage too far back. He said it would cost me to have them move it, which I wasn't happy about. (It's not my fault they didn't double check against the survey I gave them.) I told him he should at least split the difference with me or something. He said it would cost $200 to move the form. Out of the $5,680 I'm already paying, I suppose that's not as bad as it could be...

Overall, I was comfortable with how it turned out. We agreed that the garage needed to bo moved forward 4 inches, and the level of the slab could be kept the same. The garage slab looks high right now, but by the time you figure in the chain wall and the sunken floor, and the fact that the floor slopes down to the front, I think the front door will not be all that much higher than the ground level.

Progress on Slab Form

Yesterday, the crew made a lot of progress on the slab form. The material take-off from the lumber yard assumed I would need one layer of 2x12's to go all the way around. That was before I found out I needed to build the slab higher if I want to avoid needing flood vents in the front garage. It turns out I need two 2x12's stacked almost all the way around (except where the slab is lower, such as the patio and parts of the front garage. They used all the lumber from the original take-off, which got most of the form done.

The plumber can start working now. And I can get the dirt inside the form to pad it up. The slab guys will come back to put additional 2x12's later. I wasn't able to talk to the lead guy about those arrangements. When they started in the morning (around 8:30), the owner's son was with the crew. When I went back later in the day, the son was gone and another guy had been left in charge. I'm glad he could speak English! I need to contact them to find out when, and I need to order the lumber.

I brought a garbage can over there for them, also. I hadn't thought to do that on the day they staked out the pilings, and a lot of trash & debris blew over to my good neighbor's yard.

Also, the portable toilet was delivered yesterday.

We're Go for Saturday

The slab contractor confirmed that he's going to be out to stake the pilings tomorrow. I hadn't thought about having the port-o-let out there for them yet. But he said they could to the staking without it.

The First Signs of Construction??

The slab contractor I've chosen says he should be ready to skate out the piling locations this Saturday. I'm supposed to get confirmation tomorrow. He also promises that I'll have all of his insurance documentation before any work begins. We'll see.

Today I bought some piling stakes. At least, I think they're piling stakes. They're 1x2 inches and about 12-18 inches long. So I'm ready if he does show up.

I also called the power company today to see if they're received the permit from the parish to install my temporary electric. They have not. My electrician friend says it has been called in to the Parish for them to inspect the pole. But something must be holding it up. I have to call them tomorrow.

I recently went to take a closer look at the Pella windows. The jamb liner seemed like it was cheaply made (a thin, fuzzy strip). I'm going to look more closely at the Marvin and Allenco windows before making a decision.

End of the Slab Contractor Search!

Well, the contractor in my last post didn't work out. He took forever to get back to me and then wanted to charge about twice as much as the most expensive bid I have so far ($5 per square foot vs. about $2.50). No thanks. I think this is the first time someone has really tried to play me because I'm young or I'm new at this, etc.

So I kept looking. I circled back with other bidders in other trades to ask for slab references. The lady at one lumber yard gave me a name. I met this guy at the lot. His price is $1.60 per square foot, which doesn't include equipment or materials. Even so, he's about the least expensive guy I've found. This past Friday, I took my mom & dad with me to check out slabs he's done in a subdivision on the westbank. They were pouring two more slabs that day. I got to watch them for a bit and then walk through two others that are at the framing stage. The work was about the best I've seen.: flat surface with no honeycombing and minimal voids in the brick ledges. Even the areas surrounding plumbing pipes were fairly level.

I'll be contacting this guy tomorrow to put things in motion. Looks like I'm ready to begin actual construction!

Electric Pole Installed; Slab Contractor; AC Bids

My dad and I installed the temporary electric pole before Thanksgiving. My electrician/friend said that I'd need to add a 220V receptacle to pass the parish inspection. I bought most of the pieces I needed from an electrical supply store (the receptacle, a metal box to mount it in, a circuit breaker with GFI protection and a weatherproof cover). On the weekend after Thanksgiving, we went to Home Depot to buy the rest of what we needed (mostly conduit and fittings). Then we installed it. (Hooray for Jerry, an HD employee who was really helpful & knowledgeable.)

My electrician is coming to inspect it before he calls for the parish inspection. This is good since I don't want to electrocute anyone!! The funny thing is, he says that the 220V will probably never be needed during construction. But the parish requires it. At least I should be able to reuse components of it in the house.

Chain-Wall Leakage
While we were there, we also repaired a spot along my chain wall where sand was seeping underneath into the neighbor's yard. Their lot is low, and water from a rainstorm found a spot to break through under the wall. So we dug it out from both sides and filled in some concrete underneath about 4-5 inches deep and maybe 18-20 inches long. Neither me or my dad knew of anything else to do to fix it. So hopefully, it does the job.

Slab Contractor
I think I might have found my slab guy! There was a crew working on a slab up the street from my lot. I stopped and got their information. Since then, I've let him take my plans and look them over, and I've gone to see a commercial slab he did recently. It was well done, with no honeycombing or voids. Just one depression in the top where some rain water had settled. (I don't expect it to be 100% perfect.) So this looks like it might be the guy. He says he uses the vibrating rod to make sure the concrete settles everywhere. Now I just have to get him to call me back with his price! It's been a few days. I've called him a couple of times. He tells me he's been waiting to talk to his partner, who has been out of town.

Air Conditioning Bids
My preferred air-conditioning contractor has had some business and family problems that kept him out of touch for about 3 months. But he finally gave me the quote today: $14,200 for everything I wanted. That includes a 16 SEER Trane system, 4-ton, with variable speed air handler (vertical installation in the attic), electrostatic air filter, etc. While I was waiting for him, I got a couple of other bids: $12,200 and $7,900. These other two are quoting brands other than Trane. I'm not sure why the third guy is so low.

The Gears of the Bidding Process Turn Slowly... and Other Delays!

I've had a few breakthroughs in getting recommendations for subs in trades that I was having trouble with. For example, I finally brought my plans to the excellent framer across the street from me. Although timing may prevent him from doing the work, he gave me a price and he also gave me names of a slab guy, a plumber, and a recommendation for a lumber yard. When I called the lumber yard, she gave me two other recommendations for framers. My mom's friend gave me the number of a plumber he really recommends. I also had the Laplace concrete company to refer me to two other slab guys.

I've visited three slabs now done by people bidding on my job. Each one has had its weak points. Either the top was rough/uneven or the brick ledges and sides were a mess. I'm not sure how much of the sides I should worry about since they may come back and finish it off later. But the top definitely needs to be level, flat, and smooth.

I made my first attempt at a permit this week. Right away, the plan reviewer found things he needed clarified in a letter from the engineer. Apparently in Jefferson Parish, any part of a structure that's less than 5 ft from the property line needs to be fire rated for one hour. Two walls of my garage, and the overhang on one side of the house are within this limit. So I'm working on getting that letter now. At the same time, the reviewer told me the wall between the house and the attached garage needed to be fire rated and he was able to just write that in on the plans. If he could write in notes about the interior wall, why couldn't he write in the notes about the exterior walls?

Oh, and the permits office told me that they have nothing to do with giving me my address number (which contradicts what they told me over the phone). When I told him I didn't know the address number, he seemed aggrivated. So he sent someone around to figure it out. In their computer system, my lot and the neighbor's lot (which was one big lot at one time) still had the old house that straddled the dividing line. Eventually, they were able to determine that my house number is 624. During the visit, he pulled up aerial photos of the area to verify that there were indeed two lots and that a new house had already been built on the adjoining lot. I wish I could have gotten a copy of that photo, even though it was taken shortly after Katrina and still had all the trees on it.

On the positive front, the power company is on schedule to have the new utility pole installed by Nov. 1. Then I can have my temporary electricity feed off the new pole. Speaking of electricians, I'm waiting on two other electrical bids and my HVAC bid.

When visiting a slab today, I met the owner of the house who told me three things to make sure I have before my final inspection:

• Your house number posted (and make sure the numbers are large enough)
• Any steps are the right height/size, and
• Your mailbox installed

He also told me about another company besides the citizen's FAIR plan for obtaining wind and hail insurance. It's Republican Insurance. A quick Google search revealed more than one match. I'm not sure which one he was talking about, but he said you can save a lot by going through them.

Bids & Legal Stuff

Today was a busy day for a Saturday! I started by meeting with the air condition man that my family has used for years. He's a perfectionist and he knows what he's doing. So I plan to use him unless his prices are sky high.

Later, I finally got a framer to meet with me. That has been a struggle. His bid was higher than I was told to expect, at $6.75 per square foot. I look forward to getting other bids to compare to.

I also went to Luling to look at the work of one of my potential slab guys. This job is in the forming stage. The work looked neat enough. I saw another slab that had already been poured, and I wish I could find out who did that job! It looked very neat, and the finish was level and polished. My guy's work also looked okay for the stage it was at.

I also met with a lawyer who is working on the contract template I will use when hiring each tradesman. He gave me a draft of the contract, the "acceptance of work" form, and the lien waiver. He also gave me material to read so I can learn about this construction business and the issues I need to know about with Louisiana law. I'll be absorbing that over the next few days and getting back to him so we can narrow down to the final versions of the contracts & forms.

One thing I learned is that it's best to have each contract and acceptance form "recorded" with the parish. The way I understand it so far, this makes everything more official and provides backing if someone wants to make a claim or otherwise cause trouble.

Plans Complete!

This is one of those times when pieces just seem to come together at once. I picked up my final plans from the designer today. But leading up to that, some things just fell in line.

I had been waiting about a month since the last time I heard from him. Then he had another revision ready, and for the very first time I got to see things other than the basic floorplan: lighting plan, slab plan, piling plan, etc. He said that I should review and get back to him quickly so he could wrap my project up by Friday. If I was to go over a week, then he expected me to pay him at least half of what I still owed him. I See. So, it's okay for him to take weeks to do his part, but I need to give him a quick turnaround and wrap everything up because it's convenient for him?

For the floorplan, we went through about 5 revision cycles. Now, I'm certainly ready to move ahead on this, but I wasn't about to rush through everything else without thinking it through or at least understanding the notes and diagrams for the new parts of the plan. I turns out that it really wasn't a rush.

Well, one of my biggest questions centered around the elevation of the slab. There's a local regulation that your slab needs to be the higher of the base flood elevation or three feet above the crest of the street. The plans had been drawn up with a total slab height (slab + footings/chain wall) of 2 ft. I didn't understand if the designer made assumptions about the present elevation of the lot or what. How did he know I didn't need three feet to build high enough?

I asked him, and he said they made assumptions, but if it turned out I needed a taller slab they'd modify the plans. The survey would tell me if this would be enough. Thus the other piece that fell nicely in place: I had ordered the survey about 4-5 weeks prior, and I had been on the phone with them lately trying to get it done. On my way out the door to bring my last revisions to the designer, the survey company called. It was ready to be picked up. And it turns out that my lot is roughly one foot below the required slab height. That means the slab plan they came up with is fine. It'll be about a foot out of the ground, and the chain walls will be about a foot in the ground.

My other questions were answered by the designer and some research on the web. For example: 6x6 2.9/2.9 WWF is "wire welded fabric", or highway wire, the large chicken wire type stuff they put in concrete to reinforce it. So I got all my questions answered and revisions made, and today I picked up the final plans. I can still go back if I discover some final tweaks are needed by next week. Otherwise, I need to pay the designer the rest of what I owe him and take two copies to the engineer to have them stamped. Then I can go apply for the permit.

I'm going with the post-tension slab instead of traditional rebar reinforced concrete. It's a bit of a risk because none of my family knows much about this method. But I hear from friends and professionals that it's a solid concept and it's good to use in our area. I'm starting to see them used more and more around the area.

Finally, I also got a bid for my pilings. I need 54 of them, and the bid is cheaper than I expected. I braced myself for $10k-15k, but the bid is around $8,000 (~$165 per piling). I also know now that I need to put some more sand down where the house & garage will go. About another foot. So as soon as I can get over there to stake out roughly where the boundaries are, I'll schedule the delivery of the sand.

Post-Tensioned Slab or Rebar?

My architect asked me if I wanted to do post-tensioning on the slab or use traditional rebar. When using rebar, they lay a grid of iron rods (the rebar) on the ground where the slab will be poured. When the pour is done, the rods wind up suspended in the concrete to make it stronger (or at least resistent to cracking. If it does crack over time, the rebar acts to keep the concrete from separating too much. So rebar can't prevent cracks, but it does minimize them and help keep them from getting worse.

Post-tensioning embeds a grid of steel cables across the slab with extra cable sticking out around the borders. The cables are encased in plastic sleeves to keep them from rusting out over time. A short time after the concrete is poured, a hydraulic jack is used to pull the cables tight all around. Then the extra lengths are snipped off. This post-tensioning is done before the concrete sets fully. The idea is that you're putting pressure on the slab while it finishes setting. Concrete under pressure is stronger than it would be otherwise. So post-tensioning should do more to prevent cracking in the first place.

This method is newer than using rebar, at least in residential construction. Another benefit of post-tensioning is that it supposedly lets you use a thinner slab than you would with rebar. This would help you save money.

The architect also described it this way: With rebar, they have to come out and get all the rods in place in and around the trenches that need to be dug for footings, etc. If it rains before you pour, they need to come out and clear out all the sand that washed into the trenches. The rebar makes it difficult to do, so you lose time. He said this concern is reduced when using post-tensioning. I'm not sure why the having rebar there would be different than having cables there if the rain should occur. I'll have to ask him or a slab company more about it.

So post-tensioning hasn't been used as long as rebar. Hmm... Like all new building methods, I wonder how experienced local contractors are with it. Would I be able to find someone who knew what they were doing? I've only seen two houses being built around here that used this method. And is it really proven? Once a house is in place for a number of years with a post-tension slab, is it really all that it's supposed to be?