post and beam construction

The normal way of building P&B homes is using wood in the posts and beams. What if I wanted to use cement as the post? One style I've looked at uses 6x6 posts and 6x8 beams. So I figure a 12x12 post of cement should be equal? according to calculators, a post 16ft tall would require a mere 1/2 yard of cement. Any reason not to use cement as the post?
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you have to use rebar......Too..
< http://www.ehow.com/how_5558939_pour-concrete-post.html
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Richard,

First, you would want to use "Concrete" not "Cement".
Second, concrete is very strong in compression (the downward force produced from the weight of the building), but rather weak in tension (the force applied to the side of a post, or the bottom of a beam). By itself, a concrete post would not resist side to side movement from wind, earthquakes, etc. Therefore you would want to add rebar to add lateral strength. If you choose to go this route, you should probably contact an engineer to find out how much rebar would be needed and how it should be placed to achieve the necessary support. If possible, I would add shear walls somewhere to help resist that side to side movement if you were to have an earthquake, tornado, or strong flood waters.
Third, a yard of concrete is 27 sq feet (3'x3'x3'). So, your 16' post would take a little over a half yard (.6 yard). I haven't bought concrete for a while, but the last time I did it averaged about $140 a yard (material, delivery, mileage, taxes, etc.). That would make each of your concrete posts cost about $87, considerably more than a 6x6 wood post. That doesn't include the materials needed to build the forms, the cost of the rebar, and any engineering costs involved.
Fourth, attaching walls, windows, etc. will be more difficult with concrete posts than it would be with wood posts.
Unless you have a specific reason for using concrete (supporting a heavy load such as parking cars on top, or posts that will be submerged in water), I would stick with wood posts.
Just my amateur two cents.
Anthony Watson Mountain Software www.mountain-software.com www.homecookinrecipesoftware.com
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Have to agree with Anthony, on most points. Not in order, but No. 1 consult with an engineer before you go forward, any concrete columns require an engineering design. I think you'll be disappointed with what you hear from the engineer. 2. It's almost unheard of to use concrete columns except for precast/pre-stressed piling. 3. You may have seen what seem to be concrete columns that are actually steel columns encased in concrete for fire protection or appearance. 4. The cost of precast/pre-stressed columns, the attachment hardware and erection is probably more than you expect. Reconsider your construction method
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On Fri, 2 Mar 2012 21:49:32 -0500, Tom Cular wrote:

Sheeesh. Ok so by your thinking then, one must consult an engineer to build a concrete wall like for a basement of a house? I was just looking at extending the base foundation of a post for the convenience and less hassle of manhandling the bents. Now given the dimensions are equal, a post made of wood, and a post made of cement, which is stronger? The wood would snap long before the cement.
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A concrete post buried in the ground will be supported so you normally won't have the lateral concerns of a free standing post. As long as you have the necessary footprint to support the weight, you could just install a sonotube in the ground, add rebar for additional strength, and pour your concrete foundation.

Equal dimensions? Wood is easily stronger than concrete in tension. For example, take a 4x4 wood post and a 4" square concrete post with no reinforcement (both 8' long), and support both ends securely. Grab a sledge hammer and whack each in the middle. You may dent the 4x4 wood post, but odds are you can bust through the concrete post easily.
As far as which can hold up the most weight in compression, I don't know. I would tend to think the concrete would support more once you got past other factors like the post bending and breaking. The wood fibers will crush once you get past a certain level.
Anthony
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Do it one time but with a Axes Then concrete will came stronger than Wood in tension,
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Probably not necessary for a simple, low wall, but a good idea, are you capable of designing reinforcement for a wall? A plain concrete column is like a glass straw, and will support an axial load, any lateral load will subject it to failure. Concrete reinforcement does not consist of just sticking a few bars in the pour.
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Richard-
HH's (Anthony's) analysis of your proposed concept is "spot on".
Your P & B concrete (not cement) structure doesn't make economic sense.
To address your question "one must consult an engineer to build a concrete wall like for a basement of a house?"
If you can develop a design with drawings to meet your local building code.... then "no, you don't need an engineer".
It all depends on your local jurisdiction. You'd have a very hard time getting your concrete P & B approved in earthquake country without an engineer's stamp on the plans. And in non-e/q country it's probably still too no standard to get "ok'd" without an engineer's stamp. :(
Concrete & timber are very different materials. Each has it's strengths & weaknesses and thus, each are better suited for different applications.
cheers Bob
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If concrete post and beams were a good idea it would be done that way. It is not done that way.
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On 3/2/2012 9:35 AM, HerHusband wrote:

Actually that would be 27 CUBIC feet. Not square.
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Steve,

Oops, yes you are correct. That should be Cubic, not square feet. I wasn't paying attention.
Thanks,
Anthony
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Great, richard is going to set his 1968 Winnebago up on posts, instead of cement blocks. Ohio must be proud!
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Do not forget also: A vibrator for the concrete pour. A pump truck to pour the concrete. added costs to consider.
I would go standard construction.....why not. It is relatively easy to handle and cheap. No engineering required if you stay nominal. john
"richard" wrote in message
The normal way of building P&B homes is using wood in the posts and beams. What if I wanted to use cement as the post? One style I've looked at uses 6x6 posts and 6x8 beams. So I figure a 12x12 post of cement should be equal? according to calculators, a post 16ft tall would require a mere 1/2 yard of cement. Any reason not to use cement as the post?
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wrote:

I just finished a p&b house. Two story to boot. I built my own posts. Started with a 4x6. Then sistered 2x6 then 2x8 theb 2x10 and wound up with a pretty solid post. Set on a serious concrete footing and went conventional construction from there.
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