excavation sequence

OkeeDon · Apr 3, 2004

Another point, the first mixer got stuck is the loose soil. What are you going to do with a stuck mixer? 

Or one that flips over? A couple of houses ago, one that we purchased already built, we were replacing carpet when we discovered a distinct difference in the slab. I was talking to a neighbor and mentioned it, and he said, "Oh - yeah - that must be where they were when the cement truck rolled over. He was backing through the swale, hit a soft spot and fell over. No other truck could get in, and they didn't get the flipped truck out until late that night. They started over in the morning."

I've often wondered if concrete starts to harden in the barrel if a truck lays on its side for 6 hours or so...

Cliff_Johns · Apr 3, 2004

( My parents garage had a broom finish and it was always dusty, held the mud from the tires, difficult to sweep, and you could never get the oil stains off of it. I have a smooth finish on the garage floor and oil stains come up with some speedy dry and a rub of the shoe. It sweeps clean and I don't find it slippery unless it is wet and I am wearing leather soled shoes. )

OK, you've convinced me. Smooth finish it is. It also makes it easier to slide things around
including myself if I'm trying to get under something. Thanks,
Cliff

Cliff_Johns · Apr 3, 2004

(
Another point, the first mixer got stuck is the loose soil. What are you going to do with a stuck mixer? They had 20 or more sheets of 3/4 inch plywood to lay down to provide traction.
)

Not worried about that. The truck will be on the street or in my driveway.
I can't get anything wider than 5' into the yard behind my house. Whether
I do it, or someone else, they will be using 1/2 yard buggys

Okeedon's story sounds pretty scarry though. Imagine the drivers feeling
as he realizes that the whole thing is going over. Yikes!

Nevertheless, your point is well taken.

Cliff

Cliff_Johns · Apr 3, 2004

( If you cut a piece of lumber too short, you can always cut another piece. If you don't build the wall correctly, you can take it down and rebuild it again. You can't do that with concrete. If the concrete isn't level, the wall isn't level. )

OK, I get your point. I was thinking that I coud do the excavation because mistakes there could be corrected until I got it exactly right. Same for the forms. I could redo them until perfect, level, flat, square and solid.

I figured that if the excavation and the forms were in good shape, than the concrete would be something a bunch of guys could do if one us was knowledgeable and had done a lot of concrete work in the past. Level and flat for the concrete is derived from level flat forms. But as you say, it's that day when the truck shows up full of concrete and we start buggying concrete to the build that worries me. Now you've got me worrying even more.

I'm on the edge about this. I may see if I can find a concrete guy who is willing to let me do the excavation and forms (with him stoping by to check them over a few times as I go) , then let him and his crew do the pour. I might not save anything at all, but at least that way, I get some experience and I learn something. That part is important to me.

Cliff

OkeeDon · Apr 3, 2004

The truck will be on the street or in my driveway. I can't get anything wider than 5' into the yard behind my house. Whether I do it, or someone else, they will be using 1/2 yard buggys 

Have you looked into a pumping service? Just the other day, I watched a large warehouse slab being poured by trucks on the street feeding a concrete pump truck. He had a very long, extendable boom that could have reached over an average house -- the boom I saw was at least 80' long -- with a hose dangling from the end. The guy on the ground grabbed the hose and directed it, while the guy on the truck manipulated the boom. As each truck was emptied, the next one rolled up and they continued to pump. The pour was done very quickly. I have no clue what they cost, but it must be comparable to the buggies, especially considering the speed.

Junkman · Apr 3, 2004

( OK, I get your point. I was thinking that I coud do the excavation because mistakes there could be corrected until I got it exactly right. Same for the forms. I could redo them until perfect, level, flat, square and solid.

I figured that if the excavation and the forms were in good shape, than the concrete would be something a bunch of guys could do if one us was knowledgeable and had done a lot of concrete work in the past. Level and flat for the concrete is derived from level flat forms. But as you say, it's that day when the truck shows up full of concrete and we start buggying concrete to the build that worries me. Now you've got me worrying even more.

I'm on the edge about this. I may see if I can find a concrete guy who is willing to let me do the excavation and forms (with him stoping by to check them over a few times as I go) , then let him and his crew do the pour. I might not save anything at all, but at least that way, I get some experience and I learn something. That part is important to me.

Cliff
)

Cliff..... I have to tell you, that if you start digging and the area that you excavate isn't done correctly, then you have to put the dirt back in. They the concrete is going to be poured on disturbed earth and that isn't good. It is going to settle and you are going to have problems. If you want to practice using the backhoe, find someone that needs some trees planted. You are going to be living with this garage a long time and this isn't the time for you to be learning how to use your tractor. Leave this job to the professionals that know what they are doing. Would you want the heart surgeon doing your bypass surgery that was doing it for the first time on you or would you want the seasoned surgeon that has done the operation many successful times in the past. The same with the concrete and form people. Let them do the job that they are experienced with. If you want to backfill the job, that is OK. You can't mess that part up. Digging the footing, can get messed up if you dig them too deep or in the wrong area. Trust me on this, I know this from experience, not mine, but seeing it done on job sites by inexperienced operators. No one is happy when this happens. Usually they just fix it by pouring more concrete, which means more expense. Let the pros do this, and you do that which you can do best...... write the check. /forums/images/graemlins/grin.gif

Alan L. · Apr 4, 2004

Technology has changed, but I grew up in construction. My Dad built custom homes, and back then, 30+ years ago we did almost all of the work, using very few subs.

For the slab, we put up the forms first - 2 X 12 with vertical stakes on the outside, every 2 feet, nailed to the 2 X 12s with two-headed nails (so we could pull them apart later). No backfilling, as the stakes would hold the forms.

Next, we dug the beams with square shovels designed for the purpose. Beams would be dug around the perimeter and some across the slab in both directions. There was some sort of computations as to how many beams you had to have. The beams were 24" deep from the top of the form. We spread sand inside the forms to bring the concrete thickness over the flat areas between the beams to 4".

The plumber would "rough-in" the plumbing under the slab, and we would put black plastic (Visqueen) over all surfaces, as a vapor barrier. Then we will put 4 5/8" rebars in each beam, with bent pieces at every junction, using wire twist ties. Very hard work.

For the actual surface, we used 1/2" rebar at right angles leaving squares of about 16" all over. Dad scoffed at mesh reinforcement - said it wouldn't hold anything....

For brick veneer homes, we then put a flat 2 x 4 at the top of the form, inside, to make a brick ledge. The garage opening would have a 2 x 6 flat so that the garage door bottom ends up 1.5 inches below the surface of the slab, to keep water out. Before pouring the slab, the termite exterminator would treat the entire slab.

The actual concrete came from trucks, and with the long chutes, the whole slab was accessible. After pouring the slab, we sometimes ran water hoses on the surface in hot weather, and heaters to keep the slab from freezing in cold weather. Dad lost a lot of sleep during this phase of building a house.

Nowadays most of the slabs around here are post-tension. There are special lubricated cables about a half-inch in diameter inside plastic sleeves pulled both directions and extended through holes drilled in the forms. After the concrete cures the cables are pulled tight, then again in 2 weeks, at which point the ends are sealed up. They can be re-accessed later to pull the thing together again if necessary.

Alan L. · Apr 4, 2004

I just remembered that in addition to the stakes on the outside of the forms, we would put 1 by 4 planks nailed with double headed nails to the top of the form and nailed at the other end at the base of a stake about 2 or 3 feet back from the form. I don't remember if there was one of these supports for every stake, or every other stake.

OkeeDon · Apr 4, 2004

Nowadays most of the slabs around here are post-tension. 

I just heard of post-tension slabs for the first time a few days ago. I did a fair amount of research and understand how they work. Sounds interesting. It must have something to do with soil conditions, however. 99% of houses built in my area of Florida are built on monolithic slabs, and none are post-tension. In our city, over 6,000 homes were built last year, from $150K to $3 million, almost all on slabs. In my research, I saw mention of clay conditions. Our soil is 100% sand.

The ironic thing is, because our new house has to be elevated so high over the surrounding land in order to meet code of 18" above the crown of the nearest road, we're going with a crawl space and perimeter walls with columns supporting the joists. I've built the area around the house up 30" with fill from my pond, but the house floor has to be a minimum of 26" above that. The house being constructed next door is on a slab, and they built the pad up about 60", first. Now, they have a huge mound that has to be sloped to the surrounding land. We'd rather have raised porches and a few steps.

Attached is a picture of the area we built up for the house - approximately 200' x 200', so there will be a nice, gentle slope to the yard, and slope right down to the pond.

bebster · Apr 4, 2004

Don, I had the same access problem and ended up hiring a pumper. It cost $500 for 1/2 day (usually more expensive on cape cod), but I didn't have any choice. Here's a link to a picture of it pumping 20 yds of concrete into my barn footing. It's really fast and clean (no spills) and probably saved that much in labor costs compared to spreading it by hand. I'll be using again later this week to pour the walls once they are formed. No way could I do this job myself, but I did all the planning and design work.