Mixing Concrete Question

[marrt]

I’m building a new deck on my house. Due to the complexity of the design, I am building part of the deck on a temporary structure. This will allow me to suspend the deck posts of their holes and pour concrete up to the bottom of the post. This makes getting the post in exactly the right spot, and getting it level in the right spot, much easier. Because I’m doing this myself, I would like to avoid a lot of concrete mixing if possible. I know that some people use a fast setting concrete and simply pour the bags of concrete into the hole dry and then add water. You can’t get much easier than that. However, while I’m sure this isn’t as good as premixed concrete, is this technique good enough for a deck? On the concrete sites where this technique is discussed, the examples given are for fence posts, basketball goals, mailboxes, etc…. They don’t talk about a load bearing structure such as a large deck. Any opinions on this approach?

 

[DavidJ]

I wouldn't hesitate to do that for fence post and such but would not use it for load bearing applications. I would recommend mixing according to instructions and pouring. You'll have a better job.

 

[Slamfire]

I've used that method with crusher run gravel. It hasn't been washed and adding water makes it firm up. Still that has been for non structural applications.

 

[bmac]

MARRT,

While I don't have the answer to your specific question, I will offer a related comment. Of course, many people embed their deck posts in concrete and I am sure that is a fine way to do it. However, my understanding is that the preferred approach is to pour the footing and then use one of those bracket things that rests on the concrete footing. The deck post sits on the metal bracket, elevated above the surface of the concrete. As I am sure you know, this helps keep moisture away from the wood, thus preventing decay over time.

BTW, if you end up doing as you described, I think that is an ingenious approach. Were I doing it, I would premix the concrete and pour it in the hole. My understanding is the ultimate strength of the concrete is dependant upon the proper water / concrete ratio.

 

[gerard]

The method you describe is not for load bearing applications as you likley will not get a good uniform cure and also it will not set up right away until it absorbs moisture from the ground. Bringing the concrete right up to the bottom of the post and using a bracket is how I would do it. There are many sides of the debate on encasing the post in concrete. Some say it rots the post out quicket, some say it makes no difference. I say if there's debate why take the chance if you can avoid it?

 

[DieselD]

Thats not a good way to do it. Tube (12") in the ground 6"below frost line. Then gurders across Or post sitting on top.
This way if settling does accur, it can be jacked and shimmed into place.
Danny

 

[Egon]

The ultimate strength of concrete depends on the ultimate strenght of the aggragate used. The aggragate will break before the cement bond to the aggragate.

Egon

 

[ScottAR]

I'm with the others. Pour a footing and use the brackets.

As for the quick setting cement, I don't like it. I work at a big box, and if it's been raining or just overly humid on concrete delivery day, some of the bags will set up before we can get it inside! The stuff is so reactive that it pulls moisture out of the air.

The only way to "test" the bags is to handle every one. If one needs very many bags, this is a lot of work.

Long term storage (2-3 days) on a site would be difficult.

All this and $1.25 can get you a cup of coffee at the quick mart. /forums/images/graemlins/smile.gif

 

[marrt]

Thanks for all the advice guys. As I feared. No harm in asking though.

This goofy county I'm in has tough requirements that discourage the DIYer. Posts must be 6x6. Holes must be 24"x24"x24". Etc. This is for a small porch and deck. Oddly though, their "recommended" approach is to pour an 8" thick pad, set the post on it, and fill the hole with dirt. I like the idea of pouring concrete to the top of the hole and putting a bracket on the bottom of the post. However, this would take 2/3 a yard for each hole. Too much to mix for a lazy guy like me. And since I don't have any helpers, and the concrete truck can't back up to the site, getting a truck is out of the question. Guess I'll have to think about it more.

 

[RCannon]

I have one more suggestion to add to all the good ones so far...

Make yourself a wooden or plastic form, and pour 8 inch "blocks" of concrete. toss them in your pre-dug holes leveled with a little sand.
good luck. /forums/images/graemlins/smile.gif