When installing wire mesh for concrete?

[catch22]

When installing wire mesh for concrete how close to the walls should it be I think I read somewhere about 3 inches does this sound about right or can I go closer to the wall and I also have to cut around posts too.Any advice will be appreciated.

Thanks Mike

 

[rburke65]

The wire mesh is there to prevent the concrete from heaving after it cracks. You will be fine ending your mesk 3" from the enge and around the posts.......IMO.

 

[boiler7904]

2-3" is fine at the edges and around obstructions.

 

[Steve in Mi]

Agreed, 2 - 3 inches is fine.

If a picture helps here is my around post treatment.

Poly and Saran film below the Dow rigid foam, reinforcing 6 X 6 wire mesh will be in the floor pour. Note the interior foundation wall rigid foam sticking up at the inside top edge of the 8" block. Final floor thickness 5.5 to 6 inches. Steel 4 X 4 post base sets on a pier and will be 4.5" below finished floor grade.

 

[boiler7904]

Forgot to mention that you should have 1/2" expansion joint material around things like columns or isolate them from the slab in another manner.

 

[Steve in Mi]

Forgot to mention that you should have 1/2" expansion joint material around things like columns or isolate them from the slab in another manner.

And the reason you suggest this is??????????????????

 

[Torque1st]

To keep them from moving when the slab expands and contracts. Some people don't tho. Expansion joints are needed at the perimeter also.

Make sure you have a very experienced man on the hook to position the wire mesh in the slab after everyone steps all over it during concrete placement.

 

[boiler7904]

Forgot to mention that you should have 1/2" expansion joint material around things like columns or isolate them from the slab in another manner.

And the reason you suggest this is??????????????????

Slabs move. Columns typically don't. When the two come together, something has to give. It's usually the slab giving by way of cracking.

That's why you usually see a 24 x 24 diamond cutout around columns in commercial buildings or expansion joints wrapped around square / round columns. Hard to wrap expansion joint material around a wide flange section being used as a column.

It doesn't have to be done but it's cheap insurance against a possible source of slab cracking.

 

[catch22]

Thanks everyone for all the information.It helped alot.

 

[larry4406]

That's why you usually see a 24 x 24 diamond cutout around columns in commercial buildings or expansion joints wrapped around square / round columns.

Not quite. The diamond is the result of a construction sequence process. In the sequence of construction, the column pier is first, followed by the slab. Blockouts (the diamond) at the pier location are placed before pouring the slab. The blockouts permit the steel, which comes later, to bear directly on the pier and not transfer load through the slab to the pier. After the column base plates are checked for bearing, grouted, and the anchor bolts confirmed tight, the diamond is filled in. In my companies 300,000+ sf warehouses, no expansion material at the diamond fill to slab interface.

Same process in residential construction, at least here in Northern VA, except the lolly columns are not anchored to the pier, just plumbed, top welded to the steel, checked for bearing on the pier, and filled in.

 

[Offy]

The most common fault that I see in the use of wire mesh is not getting it inside the concrete somewhere close to the center of the depth. It does little good when it is bearly within the bottom of the pour.

 

[ScaldedDog]

Any problem with just using the mesh as something to anchor PEX to, with rebar-on-chairs above that? Anything I need to do differently in that application?

[/hijack]

Mark

 

[Torque1st]

Even filled in with grout the slab will break free at the diamond cut or joint, hopefully before the slab cracks. Many times self leveling urethane etc is used to fill in the diamond cut. Whatever method is used, steel then slab either with expansion material or diamond, or pier and slab then steel, -it works.

Offy, that is why I recommended a "very experienced man on the hook" in post #7 above.

 

[Torque1st]

Any problem with just using the mesh as something to anchor PEX to, with rebar-on-chairs above that? Anything I need to do differently in that application?

[/hijack]

Mark

Mark, just watch to make sure the guys placing the mud don't stomp all over the rebar and drive the chairs into the ground, -which they will...

You will still need a man on the hook.

 

[kbs2244]

Basement floors are one of the last things done on home construction around here.
Any lolly post are placed on their piers and construction done on top of them.
The basement floor concrete is shot through a basement window and poured right up to and against the posts.
Of course a basement floor is down low enough that it will not expand or contract much.

 

[Junkman]

That is the way it is done here also, but the framers forgot to put the lolly column under the steel been even though the pier had been poured for it. It wasn't noticed until a year later, when the beam had sagged and the refrigerator door wouldn't close unless you pushed it closed. The floor had sagged about 2". I got a house jack and started to lift it one turn a day, until I was going away for a week. I asked a friend to give it one turn a day, and when I came back a week later, he gleefully told me that he had leveled the floor in one day. I also had cracks in the walls and the ceramic tiles had popped. I wasn't happy, and just had to fix his mistake. I even cranked the jack down to relieve the stress, and slowly brought it back up over the next couple of months. I think if I hadn't done this, I would still be living with stress cracking problems.

 

[Torque1st]

I asked a friend to give it one turn a day, and when I came back a week later, he gleefully told me that he had leveled the floor in one day.

Ouch! That must have hurt. I guess you learned the hard way it would have been better to just to leave it alone for a week...

 

[Junkman]

Ouch! That must have hurt. I guess you learned the hard way it would have been better to just to leave it alone for a week...

It was one of those type things where I should have known that it would be a gamble to let him do it, because I knew that he always was in a rush to complete any job. He is a good guy, but his standard motto was... thats good enough for now, and we can redo it later if we have to. I on the other hand, always obsess on every detail and try to make it perfect the first time. I think that is why I don't get as much done as I should. Now, I say that I just don't have enough years left to get to everything that I want to. Sometimes retirement can be depressing, because the light you see at the end of the tunnel isn't really light, but the beginning of another era. I wonder where all the years went, and when I think about all my friends that have passed on, I get more depressed. I guess that is why I read and post on this forum. It keeps me busy when I don't want to go into the garage...

 

[Torque1st]

I know EXACTLY how you feel, I think and plan obsessively also...

I am retired also, -medically retired early. With the number of things that have failed for me that "other era" isn't going to be a long one. I can still keep going as long as possible tho.

 

[boiler7904]

Not quite. The diamond is the result of a construction sequence process. In the sequence of construction, the column pier is first, followed by the slab. Blockouts (the diamond) at the pier location are placed before pouring the slab. The blockouts permit the steel, which comes later, to bear directly on the pier and not transfer load through the slab to the pier. After the column base plates are checked for bearing, grouted, and the anchor bolts confirmed tight, the diamond is filled in. In my companies 300,000+ sf warehouses, no expansion material at the diamond fill to slab interface.

Same process in residential construction, at least here in Northern VA, except the lolly columns are not anchored to the pier, just plumbed, top welded to the steel, checked for bearing on the pier, and filled in.

And on the 350,000 sf building I was a part of construction on last year, there are expansion joints at every blockout around every column - all 300+. The 900' long building is between 899'-10" and 900'-0" depending on the season. In that instance, you put expansion joint material around anything and everything that might move.

Like a lot of things in construction, different parts of the country do some details differently. It doesn't make one way right or wrong. It's just not what your used to. In my area, you aren't putting concrete slabs to steel columns without some sort of expansion joint. Chicago gets 100 degree temperature swings from winter to summer every year. In that range of weather on a construction site, concrete is going to expand and contract - a lot. The expansion joint is merely cheap insurance to make sure that you don't end up with cracks all other the place.