when to place forms?


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Old 04-17-06, 07:49 PM
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Question when to place forms?

I will be adding several inches of gravel base to be compacted before I pour the concrete for my patio. Are the forms placed before or after the gravel base is installed?
Thanks.
 
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Old 04-17-06, 08:07 PM
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when to place forms?

Put in the base material and compact it to a width greater (1-2 feet) than your patio slab area. Then set the forms.

This way you will be guaranteed to have a good base under your patio and have a solid base to anchor your forms to. You cannot get good compaction all the way to the edge of a gravel base.

Dick
 
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Old 04-18-06, 09:20 AM
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Set the forms first, level them and set the pitch(1/4) for runoff, and then fill in the gravel to the bottom of the forms and compact. You can leave the 6" along the form without gravel so it will have solid beam of concrete. Don't forget wire mesh.
Frank
 
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Old 04-18-06, 02:36 PM
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when to place forms?

The sequence all depends on whether you are placing a flat slab or a thickened edge slab.

If you are pouring flat slab for a patio, set the forms after you have a solid compacted base. A flat slab requires a uniform base extending a distance equal to 2x the thickness beyond the slab edge.

If you are pouring a thickened edge slab to support an edge loading, the you need the extra depth for the load and because you cannot compact the base well enough around and in the bottom of a trench with steep sides.

How many roads (really long patio) are built with thickened edges?

Dick
 
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Old 04-19-06, 12:43 PM
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If you ask me it is easier to fill after the forms are in. Only because you can easier see how much fill you need to add to make it all the correct slope. My opinion - forms first.
 
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Old 04-20-06, 07:41 PM
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Right on Tommyboy
How many Patios are poured with 2 feet of compacted stone around them, is this for a rock garden? For a patio you dont need the base to extend from under it, the weight of a patio is down not out. The thicker edges on a patio will make it stronger and also when you look at it from the side you dont want to see the gravel under the concrete, depending on the slope of the yard, this way you have a nice step rather than dirt ramped up on the sides.
How do you place and compact the gravel without the forms, do you have to dig the gravel up later to set the forms properly or do you use a expensive laser level to set the grade, because Im sure homeimprov2006 has access to one.
Frank
 
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Old 04-20-06, 08:48 PM
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when to place forms?

************* there are several types of slab construction.

It depends on what kind of a slab you are placing (although you probably pour concrete and not place it).

Also, 2x the skab thickness is not 2 feet unless you erroriously think the thickened edge is really the slab thickness. Whenever you put a vertical load on soil, there is a force outward depending on the type and quality of the soil. This is the reason for the slight extra width for the base. It is also easier, more reliable and more economical for a typical flat slab.

For a patio, the loads are so small there is no need for a thickened edge (and extra cost and time) unless you have an elevation peoblem.

There are advantages to both and that is why there are two different types.

Have you ever seen a highway slab with a thickened edge?

Dick
 

Last edited by mattison; 04-21-06 at 05:23 AM. Reason: Be nice. Everyone has their opinion.
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Old 04-21-06, 02:38 AM
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I have to agree with the forms first method. It is easier to determine how much stone you need when you can see it right in front of you. If you're going to plant anything around the perimeter of the patio, the extra stone extending outside the forms would be a big pain. We're talking about a residential patio here, not the interstate highway system. If you don't get perfect compaction right at the form line, so what? The heaviest traffic on it will probably be Big Uncle Ed at the Fourth of July party. Either method would work though. Good luck.

Pecos
 
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Old 04-21-06, 02:41 AM
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To clarify Frank's first post on this topic, I think he means you should set the slope at 1/4 inch per foot, not 1/4 inch total over the whole patio. Good luck.

Pecos
 
 

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