poured concrete wall house

[eng003]

Interested in information and experiences with poured concrete wall construction for a house. Do you use just a mat of reinforcement bars or do you utilize wwf as well? Owner wants to construct himself "slowly" presumably mixing his own concrete. He is going to have cold construction joints all over the place right...how will this effect the wall strength? If you were going to construct the walls slowly, could you have some kind of moving formwork that you could creep up the walls? Any good reference reccomendations for poured concrete wall construction?

 

[dik]

Have you looked into insulated concrete forms, aka ICF, construction... Do a quick web search...

Dik

 

[dhoward26]

ICF's are pretty slick. Look into "PolySteel". I think ARXX is taking it over though (or has, just hasn't adopted all of the PolySteel standards yet). I can send you a polysteel design guide if you're interested in it.

 

[eng003]

I am familiar ICF and like them as well; however, this guy is not interested in this technique.

 

[dik]

Is this for a foundation wall? or for the main building walls? What type of basement?

Dik

 

[eng003]

No basement, poured concrete walls will be exterior bearing walls for two story house.

 

[dhoward26]

Why isn't he interested in the ICF's? It will more than likely be less expensive than doing standard reinforced concrete walls.

I don't have any experience with an owner wanting to do concrete pours at his own leisure creating a load of cold joints...not that it can't be done, but it seams a little odd. I would be very hesitant as it is if he is going to mix the concrete himself as well.

 

[eng003]

dhoward26; don't have a good answer for you on why he wants to do it...but he seemed dead set on it, and he claimed he built similar house in same way...mentioned something about carrying all those bags up some hill on the last one ...its seems odd to me to. But nonetheless; although all those cold joints would be undesirable, as long as each cold joint were sufficiently rough (1/4" amplitude) there shouldn't be a problem right?

 

[dhoward26]

Yeah. I guess it wouldn't be much different than pouring large retaining walls or columns in lifts. Just seams like a lot less quality control. What strength of concrete are you specifying?

He must REALLY want to save money on labor if he is carrying bags of concrete to build it!!!!

 

[dhoward26]

Also, I wouldn't use WWF for walls.

 

[dik]

WWF?

Dik

 

[TXStructural]

In this application, I would recommend WWR - welded wire reinforcement (aka, welded wire fabric) simply to hold all the small pieces together, which is in essence what he wants to do. The wire will provide a good density of wire crossing the cold joints. He could use dimension lumber climbing forms by setting a vertical waler with the form wood wedged away from the vertical (so it can be removed after placement without moving the vertical.) The expense would be low, but getting formwork off and moved requires constant cleaning and attention to plumb and level. I would discourage setting tall forms and concreting slowly, since the forms may accumulate debris, like leaves and trash. A leaf blower is handy.

Also, hand mixed, bagged concrete will assure a poor quality control and lack of uniformity (mixing conditions, water quantity, etc.) It might be good enough, but I would plan on 2500 psi, max. Also, the cold concrete needs to be wet to SSD prior to placing fresh concrete, and formwork needs to be coated with form oil or a needs a surface that will prevent drawing out the mix water.

Additionally, if the steel reinforcement is left exposed for long periods (more than a few months, especially in severe conditions, like near a coastline), there could be an issue with corrosion. Light rust would be fine, but flaky rust could be a problem if the guy takes years to finish the project.

 

[dhoward26]

dik,

it was in the original post asking if WWF or reinforcing bars should be used.

TXStructural,

Can't say I have ever seen WWF used or spec'd for walls before?

 

[hokie66]

I once was asked to inspect a house where all of the walls, internal and external, were cast in place concrete, 3" thick, with no reinforcement. One saving grace was that the roof was cast in place concrete as well, which I hope was reinforced. Looked in perfect condition. Basically same as a single skin unreinforced masonry bearing structure. Don't know why anyone would want to do it that way.

 

[dik]

dhoward:
Thanks... couldn't get past the Welded Wide Flange... and WWF or WWM is often used for precast wall panels... never seen for CIP concrete stuff, though...

Not sure why conc above grade unless ICF, maybe a bunker? To me, wood makes more sense, easier to keep cool with concrete, though...

If he has successfully built one before, he should use the same technique...

Dik

 

[TXStructural]

Actually, I am planning an above ground, exposed concrete workshop in my backyard as we speak. Partly for maintenance, partly for the aesthetic (I like the look of lumber-formed concrete), partly for thermal characteristics, and partly for security. ICF is the way to go for most applications, but only if you want to expend for cladding outside and drywall inside. Depending on climate, exposed concrete makes good sense. I am on ACI 560 (the ICF committee), and we have seen a number of builders move from ICF (foam on the outside) to cast-in-place sandwich panels (foam on the inside) in some applications. That said, my wife and I and one laborer erected and cast ICF walls on a 1000 s.f. rectangular barn building in a day and a half.

As to WWR (mesh), the proposed construction will have lots of cold joints, and unless there is a bit of reinforcement crossing each joint, the concrete "pieces" would function as irregularly-shaped concrete bricks. CMU works because there are flat horizontal surfaces with voids which encourage key formation by the mortar. You would not get these with the one-bag-at-a-time method. WWR can successfully be used in walls anywhere pre-placed reinforcement is used. I was in a wire plant last year where they were producing 8 ft by 30-40 ft sheets of 1/2" deformed wire mesh for use in water treatment plant walls. Obviously, it is not really popular on residential and light commercial job sites since it has to be handled with a crane of some size. In the application proposed, the guy could easily carry either #3 bars or typical sheets of builder's mesh. (The rolls would be unworkable unless he was willing to carefully flatten them - an almost impossible task.)

Haiti had lots of unreinforced (or poorly constructed reinforced) concrete walls supporting concrete roofs. A reason the death toll was so high. When the ground started moving, there was nothing to encourage the roof to move, so the walls broke and let the roof fall.

 

[jimkinney]

Didn't design it, but live in one. Based on other housed built after mine, it has re-bar not WWF. Single pour, so no cold joints, but there are no control joints. Settling cracks pop up all around so have to keep after it with caulk to keep sealed. Being in hurricane country this is a priority maintenance item. Some of the houses in the neighborhood leak so bad that mold is an issue. Builder went bankrupt to keep from having to repair them.

Next home will be ICF or filled CMU.

Jim

Jim Kinney
Kennedy Space Center, FL