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dbhansen 08-31-2007 07:41 AM

Aggregate required under footing?
 
I am going to pour an 8" deep x 16" wide concrete footing under the frost line (4' down), with a block wall on top of it going up to grade. The soil is very heavy, solid, red clay. Do I need to have aggregate under this foundation for drainage, or can I pour the cement directly onto the soil? Usually, I believe 6" of stone is recommmended, but is it necessary for an oven footing this deep, in clay? The bottom of the footing will be 54" below grade, if that matters.

And ... is there any reason not to use standard ready-to-use Quikrete for this footing?

- Daren

asudavew 08-31-2007 08:33 AM

Re: Aggregate required under footing?
 
Most would tell you to put gravel under it, but I wouldn't. I would just pour it.
And you can do it in sections. Like the front, side, back, and then the last side.
But just make sure that you leave rebar sticking out from a completed section into the next section so that they support one another. And I think footings should be twice as deep as the width of the block. You should check into this though. The friction on the sides helps to support the weight.


Good luck!

Unofornaio 08-31-2007 09:06 AM

Re: Aggregate required under footing?
 
You mention clay I'm sure to indicate firmness but remember the trade off for clay soil is it does not drain well at all. If others are using gravel in your area then I would say use gravel. The thing with footings is, there are different conditions in each area and a plan details will usually have the proper engineered footing for that areas soil conditions. All footing are not the same. Will you be OK without gravel..probably is it worth the time and effort to find out what others are using? defiantly

Keep in mind the weight these ovens exert per sq" on the footings is enormous compared to a room addition.

Bagged mix will work just fine.

dbhansen 08-31-2007 09:38 AM

Re: Aggregate required under footing?
 
Thanks for the replies! I took your advice and checked with a local mason who has some experience with ovens. He said I should be fine without the aggregate. He also suggested I get a ready-mix truck to come in because the Quikrete may not be strong enough, so I may investigate that....

dmun 08-31-2007 09:39 AM

Re: Aggregate required under footing?
 
IRC (international residential code) for 2006 from rumford.com:

Quote:

R1001.2 Footings and foundations. Footings for masonry fireplaces and their chimneys shall be constructed of concrete or solid masonry at least 12 inches (305 mm) thick and shall extend at least 6 inches (152 mm) beyond the face of the fireplace or foundation wall on all sides. Footings shall be founded on natural, undisturbed earth or engineered fill below frost depth.
In other words, if the soil hasn't been previously disturbed, it's better to cast your 12 inch footing directly on soil rather than gravel. About those bags: a foot of concrete is a LOT of concrete. Buying sand, gravel, and portland is more economical in those quantities, but if having it pre-measured and ready to mix is worth it to you, then by all means.

Unofornaio 08-31-2007 10:16 AM

Re: Aggregate required under footing?
 
At CA H.D. prices a yard of bagged mix will cost you $127.20 not including tax

Thats 40 80# bags @ 3.18ea. Like I keep saying its not worth it to mix by hand. Concrete out here right now is 95.00 a yard.

The bulk materials are going to cost very close to what your redi-mix is gonna charge then you have delivery or pick up of each material and then the joy of mixing for hours...

As far as strength In my area the bagged mix is actually a much better product than what I'm getting now from the redi-mix companies. The upped addition of chemicals and alternate aggregates almost ensures plastic shrinkage cracking with every pour.

"constructed of concrete or solid masonry" solid masonry for a footing?

dbhansen 08-31-2007 10:48 AM

Re: Aggregate required under footing?
 
Ugh, 12-16" thick for the below-frost footing?!? I was relying on someone with lots of construction experience who said 6-8" thick is enough. Are we comparing apples to oranges (footing vs. foundation)? If I get a ready-mix truck in here, I might as well go at least 12" I guess. Just more tough digging! Thanks for the replies.

P.S., I checked on ready-mix delivery, and that's definitely the way to go! For a 12" deep footing 16" wide (1.25 yards of concrete), cost will be about $200 delivered versus about $170 for 60# bags of Quikrete. Now that's a no-brainer if I ever saw one!

Archena 08-31-2007 06:25 PM

Re: Aggregate required under footing?
 
Quote:

Originally Posted by Unofornaio (Post 14614)
...

"constructed of concrete or solid masonry" solid masonry for a footing?

I wonder if that's an artifact of pier construction?

DrakeRemoray 09-01-2007 08:34 AM

Re: Aggregate required under footing?
 
I have clay soil here too, digging was a B!tch!!! My sympathies...

Just make it as deep as you can handle it, I am sure it will be fine. When I was planning mine, one of my engineer friends said I needed more, larger footings than I had already dug and formed. One of my construction friends said, if you ask an engineer, all the 100 year old houses downtown are going to fall down tomorrow due to inadequate foundations...

Delivery is the way to go on the concrete...

Drake


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