Concrete formwork in the desert?

[mzbk2l]

NOTE: not my work here - just looking for comments to help me learn.

I'm working in another desert right now that has a climate and landscape very similar to mine at home in Arizona. Yesterday morning this was a cleared piece of dirt, today it looks a little different.

I have very little knowledge of concrete and formwork, so I've been doing a lot of reading online. I was excited today to see one in process that I could get pictures of - the layout looks almost exactly like I would have to pour at home in AZ for a 30' x 40' garage. (The slab in the pictures will be 11m x 17m, or about 36' x 55'.)

Anyway, looking for comments or feedback on how the forms were set up, and what you think of the double layer of wire mesh. I don't speak Hindi, so I wasn't able to get exact thicknesses of the concrete, but one of the safety guys stuck his tape measure into the forms and estimated 50cm at the edges and 12cm in the center. (About 20" and 5", respectively.)

Is double mesh worth anything? How about their method for separating it?

First pic: walking toward it.

Second pic: right front as seen in the pic above.

Third pic: still in the right front.

Fourth pic: still in the right front, good shot of the chairs for both layers of rebar.

Fifth pic: still in the right front, all the rebar bent by hand tools on site.

Sixth pic: still in the right front, looking across the front.

Seventh pic: now in the left front, view of the double mesh.

Eighth pic: still in the left front, last picture.

What do you think? Good work? Similar to what's done in the US? Overkill? Would the extra mesh or rebar chairs cause trouble later when drilling for anchors for a lift?

At the rate they're moving, I may have some finished pics available to post soon.

 

[mzbk2l]

I just went back before lunch and the crew is gone, so I snapped a few more pictures. This time I took a look at how they finished off the wire mesh, along with a bevel strip they nailed to the top of the forms.

Pictures 9-16 are again taken from the right front and left front corners of the work site. Take a look at the white strip along the top of the forms.

Ninth pic:

Tenth pic: note that the chairs are all tied down, and the layers of mesh are tied together at some points.

Eleventh pic:

Twelfth pic:

Thirteenth pic: trying to show the depth from the top of the forms to the wire mesh.

Fourteenth pic: looking up from below the wire mesh.

Fifteenth pic: See the beveled edge?

Sixteenth pic: (this one shows the construction of the conduit they used for the bevel.

 

[mzbk2l]

The last shots are more of the way the framework is secured to the ground. Like I said, I'm trying to learn enough of this stuff to decide if I want to try to do some of it on my own as I get ready to build my garage this year.

Again, comments welcome on whether these are good practices, the same as it's done in the US, or where improvements could be made.

Seventeenth pic: using rebar for stakes, secured to the frame by bent nails.

Eighteenth pic:

Nineteenth pic:

Twentieth pic:

Twenty-first pic: note the stakes on each side of the bracing frame.

Twenty-second pic:

Twenty-third pic:

Twenty-fourth pic: a final overview of the nice straight lines of overlapping mesh.

 

[Steevo]

Do you have any idea what that slab will be used for?
That is some very heavily reinforced concrete.
I can only wish my shop slab was built that well.

 

[Dan in Pasadena]

Steevo is right that that is a heavily reinforced slab with a perimeter footing. There are aspects of this forming I don't recognize like the outer wood beam on grade that the "kickers" from the primary formwork back to this beam.

You use the term "mesh" freely and mesh connotes welded wire fabric or WWF as it is frequently called out on drawings here. There is NONE of that in these photos that I see. It's all rebar. In the states for a typical garage slab you really MIGHT use WWF, depending if its just a 3-1/2" slab on grade or whether it will support a second story or heavier than usual loads. You would probably NOT use use upper and lower rebar in a typical garage slab, though you could have a footing.

Also, you mention drilling your slab for anchors for a lift - but if you KNOW you're going to put in a lift AND you're placing a new slab, why would you not use embedded fasteners in a deeper section in the known lift column locations? That's a no brainer. NO need to consider if you'll hit/cut rebar.

Here in the States, you will have to secure a permit and get an inspector to buy off on your forming and reinforcement before any concrete is placed. By that time all your errors will have been identified and you will have fixed them or you will not be allowed to place it. - In your case, don't be deterred by your lack of experience just understand your limits. And remember that the wise man knows he doesn't know everything and he seeks the help of QUALIFIED people to make what he does better.

Good luck and by the by, WHAT THE HELL are you doing so far from Superstition Mountain?! lol

 

[RivennHewn]

Looks pretty standard for a commercial job. A bit overkill for a residential garage.

 

[mzbk2l]

Do you have any idea what that slab will be used for?
That is some very heavily reinforced concrete.
I can only wish my shop slab was built that well.

I wondered if it would be complete overkill for just a personal shop with a 2-post lift. It's fun to watch, though. Not sure yet what the purpose is.


When I came out to look this morning, they had brought in the Mercedes products...

Twenty-fifth pic:

Twenty-sixth pic: the pump rig

Twenty-seventh pic: typical concrete pouring picture; that's a vibrating (screed?) that they're carrying in to place at the back of the picture.

Twenty-eighth pic: placing another board that I couldn't figure out. Surely they weren't going to use a board for a level with that nice metal one in place?

Twenty-ninth pic:

Thirtieth pic: oh, that's what the board is for.

Thirty-first pic:

Thirty-second pic: just some scenery.

 

[shoturtle]

How are they keeping the concert moist when it cures?

 

[Garage5.9]

Is this in afghanistan ?

 

[mzbk2l]

Steevo is right that that is a heavily reinforced slab with a perimeter footing. There are aspects of this forming I don't recognize like the outer wood beam on grade that the "kickers" from the primary formwork back to this beam.

You use the term "mesh" freely and mesh connotes welded wire fabric or WWF as it is frequently called out on drawings here. There is NONE of that in these photos that I see. It's all rebar. In the states for a typical garage slab you really MIGHT use WWF, depending if its just a 3-1/2" slab on grade or whether it will support a second story or heavier than usual loads. You would probably NOT use use upper and lower rebar in a typical garage slab, though you could have a footing.

Also, you mention drilling your slab for anchors for a lift - but if you KNOW you're going to put in a lift AND you're placing a new slab, why would you not use embedded fasteners in a deeper section in the known lift column locations? That's a no brainer. NO need to consider if you'll hit/cut rebar.

Here in the States, you will have to secure a permit and get an inspector to buy off on your forming and reinforcement before any concrete is placed. By that time all your errors will have been identified and you will have fixed them or you will not be allowed to place it. - In your case, don't be deterred by your lack of experience just understand your limits. And remember that the wise man knows he doesn't know everything and he seeks the help of QUALIFIED people to make what he does better.

Good luck and by the by, WHAT THE HELL are you doing so far from Superstition Mountain?! lol

Thanks, Dan. Told you I don't know much about this. I thought all rebar was just the single strands, and assumed that when it was welded together it was mesh. Now I won't look like a dummy when I'm asking about it next month...

That's good news about the inspector. I'd like to do as much of the manual labor as I can, but I'll definitely need professional advice as I proceed to make sure I don't make any expensive errors.

I went far away from my mountain to earn some money to build my garage, of course!

How are they keeping the concrete moist when it cures?

Typically over here, I've seen them throw some canvas-looking cloth over the job and keep it wet, and maybe cover that with plastic. This concrete has only been down for about 2 hours, but it's not covered yet. I'll keep checking back throughout the day to see if they cover it.

I went and talked to one of the guys who speaks English, and he said they'll be finishing the other 1/2 of this pad tomorrow, and the whole job will be done in 10 days.

By the way, they're Turkish, not Indian as I wrote in the OP.

Is this in afghanistan ?

Nope, I'm in the other desert over here... the cradle of civilization, as it were.

 

[wssix99]

As I think was said above, that's not wire mesh. Its an actual reinforced slab. It looks that the reinforcement is needed due to the shallow foundations and to tie the grade beams in together.

If it had a deep foundation as is found in the US, they could do a simple slab on grade with no reinforcement.

There was another thread here a couple days ago regarding a post tensioned slab in Houston, again with the shallow foundation. Its a similar thing with a different reinforcement method. http://www.garagejournal.com/forum/showthread.php?t=153757&highlight=tension

Depending on your local costs for materials, it may be less or more expensive to build a slab and foundation this way. I would guess that in the desert, one would want to minimize the material and heavy equipment you need to haul to the site - so this method may be the most economical compared to a deep foundation and slab on grade.

 

[NUTTSGT]

I'd say it looks like decent formwork and pour. The form work is nothin gmore than basic lumber, something you might have found here in the US before the advent of forming stakes steel panels. You'd probably see the same thing on small constrcution or DIY pours across the country.

 

[mzbk2l]

As I think was said above, that's not wire mesh. Its an actual reinforced slab. It looks that the reinforcement is needed due to the shallow foundations and to tie the grade beams in together.

Yep, Dan in Pasadena schooled me on that.

If it had a deep foundation as is found in the US, they could do a simple slab on grade with no reinforcement.

Some parts of the US - I'm from Arizona, and if I remember right from seeing my house built, it was done in a similar manner. (My house is post-tensioned, though.)

I'd say it looks like decent formwork and pour. The form work is nothin gmore than basic lumber, something you might have found here in the US before the advent of forming stakes steel panels. You'd probably see the same thing on small constrcution or DIY pours across the country.

Ahhh, good point, NUTTSGT. I haven't watched enough formwork in the states to notice that.



Now I have to consider if the cost of buying lumber to build forms myself would outweigh the cost of having a concrete company with reusable forms come in and do it for me.

 

[NUTTSGT]

Ahhh, good point, NUTTSGT. I haven't watched enough formwork in the states to notice that.



Now I have to consider if the cost of buying lumber to build forms myself would outweigh the cost of having a concrete company with reusable forms come in and do it for me.

Depending what your are building, sometimes if you can keep the excess concrete off the form boards, you can reuse them elsewhere. If you stroll through my refurb thread, you can see how I formed boards up. Every board was reused at one point or another. . . even if it was used just once more. . .as kindling.

Keep strolling through the gallery section, you can learn alot simply by watching, reading and asking what others do.

 

[Nighttrain]

Something about the local tells me our tax $$$ is paying for that slab. THey did a very nice job on it.

 

[signcrafter]

I don't know much about concrete forming either but it looks like they know what they are doing. Most of the time in the US around here they just use rolls of wire mesh, no rebar.

As for the forms, plywood and 2x4s are pretty cheap. Not sure how deep of footings you will need but if under 16" you can get 3 eight foot rips out of a sheet of ply. So each sheet will give you 24 feet of forms.

 

[Toolfool]

What they built is typically called a 'monolithic' slab, slab and footing poured all at once. They're done mainly in areas with shallow frost lines (like Arizona). The amount and size of rebar is determined by what you plan to put in the building, and approved by your local building department. The beveled edges accomplish a few things, they allow easy water runoff, and in this particular case most likely prevent the edges of the slab from breaking off as heavy machinery is driven from sand onto concrete.
IMO, your first step should be to contact your local building department and establish a good conversational rapport with them. Usually, if they feel like you're trying to do things the right way, they're more than happy to work with you and help you out.

 

[JimVonBaden]

This is my 20X20 in Northern VA. We get some shallow frost, but not much.

As you can see, it was not nearly as extensively done as the one you are seeing. I suspect that one is designed for some very heavy work. That, or mine was way under done.

Jim

 

[signcrafter]

This is my 20X20 in Northern VA. We get some shallow frost, but not much.

As you can see, it was not nearly as extensively done as the one you are seeing. I suspect that one is designed for some very heavy work. That, or mine was way under done.

Jim

Couple questions. How come they don't run the plastic vapor barrier under the footings? Looks like it just goes under the slab? Also, how come they ran the "trough" past the garage door by about 6-8" from the looks of it? Most of the slabs I see around me everything is "flat" and then by the door they just slope it a little. I"m trying to picture how the framing and garage door work on your slab? Any picture of the door closed meeting the floor?

 

[JimVonBaden]

I'm not sure why they didn't put the vapor barrier under the footing. Is it needed?

As for the "trough", it is where the door closes. The driveway slab into the garage slops towards the garage, so the trough is used to ensure that water doesn't go under the door and into the garage, I am assuming. Here are a few pictures:

Jim

 

[Stuart in MN]

What they built is typically called a 'monolithic' slab, slab and footing poured all at once. They're done mainly in areas with shallow frost lines (like Arizona).

Thickened edge slabs are used in all parts of the US, for instance they're pretty common in Minnesota. My garage has one.

 

[signcrafter]

I'm not sure why they didn't put the vapor barrier under the footing. Is it needed?

As for the "trough", it is where the door closes. The driveway slab into the garage slops towards the garage, so the trough is used to ensure that water doesn't go under the door and into the garage, I am assuming. Here are a few pictures:

Jim

I see, thanks for the extra pics. I'm not sure if the plastic is needed under the footings. Just seemed weird that they put it under the slab part but not the footings but I don't know much about concrete so was just asking. Nice looking garage!

 

[signcrafter]

Thickened edge slabs are used in all parts of the US, for instance they're pretty common in Minnesota. My garage has one.

How deep are your "thickened edges"? Are they below the frost line? Any advantages/dis-advantages as to doing it this way instead of pouring a footing/stem wall and then pouring the slab? As you can see I don't know much about concrete!

 

[henrysgarage]

I am helping a buddy with his garage and I asked the cement contractor about poly and he said it is mainly to keep the moisture in the cement and not wick into the ground etc. I would think it would serve the same purpose under the trough also. Since he is putting 3" solid insulation under the slab no poly is needed.

I would think that water would gather under the door, which should be at the same level as the floor. The original owner who did my floor has the entrys beveled down towards the laneway.

 

[Stuart in MN]

How deep are your "thickened edges"? Are they below the frost line? Any advantages/dis-advantages as to doing it this way instead of pouring a footing/stem wall and then pouring the slab? As you can see I don't know much about concrete!

The edges of the slab look like this (this is just the first picture I found online, the exact dimensions may vary a bit.) This type of slab 'floats' in that it can go up and down with frost heaves as the weather changes, although in actuality I don't think they move very much at all. They're fine for a detached garage but you can't use them for a garage that's attached to a house with a conventional foundation, as the house won't move but the garage slab can. I believe most areas have limitations on how big the garage can be and still use this type of construction.

 

[mzbk2l]

I haven't followed up with any updates in a few days because not much of interest has happened. They poured the other half, saw cut the pad, and removed the form work. Surprisingly enough, they did not cover or wet the concrete after the pour.

I snapped a couple of pictures this morning to show where it is now.

 

[camarotoolman]

Here, Fl. we use 2x10 0r 12 to form up the edges. Them stake then and back fill with dirt from your pad. Footers are 12x12 with 2 1/2 rebar, 3 for 2 storey. Wire mesh or fiborglass in the floor. After the pour wash off the lumber for reuse later. All that rebar in the pic is over kill, unless you are building a steel mill or something. imo

 

[Falcon67]

Here, Fl. we use 2x10 0r 12 to form up the edges. Them stake then and back fill with dirt from your pad. Footers are 12x12 with 2 1/2 rebar, 3 for 2 storey. Wire mesh or fiborglass in the floor. After the pour wash off the lumber for reuse later. All that rebar in the pic is over kill, unless you are building a steel mill or something. imo

About the same here. I did 12x12 footers with three 12x12 cross beams and one 12x12 long beam, 2 #5 bars in the footer and beams. #4 bar 18" on center across the slab on chairs. It ain't goin' nowhere. About 62,000 lbs worth of concrete in there. Used 2x4 and 2x6 form boards as required and let the ground be part of the footer forms, slab is 4" off grade, no relief for the big door.

 

[nehog]

The edges of the slab look like this (this is just the first picture I found online, the exact dimensions may vary a bit.) This type of slab 'floats' in that it can go up and down with frost heaves as the weather changes, although in actuality I don't think they move very much at all...

This is very similar to the slab my shop is on, and I've tried to measure movement with frost. To date, I've seen virtually no movement in the winter.