# concrete porch



## am1too (Dec 30, 2009)

A friend wants me to do a concrete slab porch.

I am wondering how thick the concrete should be?

What would be the problems with a 2 inch slab? I do think that might be to much on thin side.

I know thicker is better. 

I am thinking 3 inches would be very servicable long term. Will be using 4,000 pound concrete.


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## bignugly (Jul 13, 2011)

am1too said:


> A friend wants me to do a concrete slab porch.
> 
> I am wondering how thick the concrete should be?
> 
> ...


We always used 2x4's for forms then your concrete would be 3.5 inches. I would go no less than that and make sure reinforce with wire mesh. Should use expansion material wherever slab meets foundation also. That is the best thickness to use unless you are running cars or pickups over it.


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## MushCreek (Jan 7, 2008)

I agree- 2X4 forms minimum, with a real footing under it. Porches have a way of becoming enclosed rooms over the years.


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## gobug (Dec 10, 2003)

I made a porch using 2x8 redwood for the frame and 1/2" thick ferrocement for the porch surface. I stapled expanded metal lathe to the frame then parged a mix of portland, flyash, fine sand, and acrylic additive. Portland + flyash to sand was 1 to 2. After 24 hrs, I repeated another layer of lathe and cement. Two years later I added tiles to match the house interior.


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## am1too (Dec 30, 2009)

bignugly said:


> We always used 2x4's for forms then your concrete would be 3.5 inches. I would go no less than that and make sure reinforce with wire mesh. Should use expansion material wherever slab meets foundation also. That is the best thickness to use unless you are running cars or pickups over it.


Thanks. I forgot about the expansion material.

Great input about the footing. She does have plans to enclose later.


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## RonM (Jan 6, 2008)

Do a 4 inch pad with a monolithic pour.....


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## bignugly (Jul 13, 2011)

am1too said:


> Thanks. I forgot about the expansion material.
> 
> Great input about the footing. She does have plans to enclose later.


I forgot one other thing too. You want to slope the slab away from the house to prevent leaking. It only has to be 1/12 pitch.


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## am1too (Dec 30, 2009)

bignugly said:


> I forgot one other thing too. You want to slope the slab away from the house to prevent leaking. It only has to be 1/12 pitch.


That I didn't over look. Want water to go away from the house. Half inch a foot is good enough.


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## RonM (Jan 6, 2008)

Half inch a foot fall is way too much= a 12 ft pad would have 6 inches of fall....not a chance....half inch would probably be enough for the entire slab, not much more than that......


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## bignugly (Jul 13, 2011)

am1too said:


> That I didn't over look. Want water to go away from the house. Half inch a foot is good enough.


1 inch over 12 feet slope


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## nathan104 (Nov 16, 2007)

Do not do a 2" slab. If you do, you may end up losing a friend. If she has plans to enclose it, go with a 4" slab with reinfocrement.


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## am1too (Dec 30, 2009)

RonM said:


> Half inch a foot fall is way too much= a 12 ft pad would have 6 inches of fall....not a chance....half inch would probably be enough for the entire slab, not much more than that......


Well I was guessing at the i/2 inch per foot. Actually I plan on half a bubble on the level. That is what my plumber neighbor says works for sewer line. I did that on some drainage and it worked fine.

Her problem is some contractors took her money and ran while doing crappy work. The drainage problem was an uneven ditch 3 ft wide draining up hill no less. The entry of the drain under the walk was lower than the outlet on the down hill side.


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## am1too (Dec 30, 2009)

bignugly said:


> 1 inch over 12 feet slope


That is about flat isn't? I'll look at some water on that kind of slope. I have 10 acres to play with. I'll also look at the current proch which is a 1/4 to 1/2 lower at the slab. Has a nice little incovient ramp at the door.


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## am1too (Dec 30, 2009)

nathan104 said:


> Do not do a 2" slab. If you do, you may end up losing a friend. If she has plans to enclose it, go with a 4" slab with reinfocrement.


I thought 2" would be a little thin so I told her a min of 3". I am wondering why you suggest 4". That would be enough to park a car on. What is the code for a house slab?


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## arnie (Apr 26, 2012)

3 1/2 - 4 inch thick .what about frost heaving you can dig some post holes say one 6inches in from each corner and one in the center to below the frost line if your in a cold area definatly use reinforcement wire on the other end before ready mix and on flat slabs the dry tamp method was to mix stone sand and portland dry and compact it in tne forms then dampin and pour a thin layer of wet cement on top this is an old method used where mixing had to be done by hand. .but seriously a 2% grade (is the most fall or slope needed that's about 1/4 inch drop per foot for a porch or floor 1/8 inch per foot is better


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## am1too (Dec 30, 2009)

Hey thanks for all the imput.

I am wondering about a temp kind of deal since she really want to get moving on this but lacks money.

What about using patio blocks more less to get something besides dirt. I have some in the open weather and have a fairly even area. Only sunk in one small spot. This would be on hard pan sand. IOW it can be shaved opposed to scooped.


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## am1too (Dec 30, 2009)

arnie said:


> 3 1/2 - 4 inch thick .what about frost heaving you can dig some post holes say one 6inches in from each corner and one in the center to below the frost line if your in a cold area definatly use reinforcement wire on the other end before ready mix and on flat slabs the dry tamp method was to mix stone sand and portland dry and compact it in tne forms then dampin and pour a thin layer of wet cement on top this is an old method used where mixing had to be done by hand. .but seriously a 2% grade (is the most fall or slope needed that's about 1/4 inch drop per foot for a porch or floor 1/8 inch per foot is better


Great idea especially with the pre mix bags we have these days. I set posts kinda like that. Pour in the mix dry and get the post straight, then water. Did that with my outside frost water bib too. Put in the gravel in the bottom. Then anykind of barrieron the gravel and covered with an inch or 2 of premix filled the rest of the hole and another small layer of premix.


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## arnie (Apr 26, 2012)

Lay your patio block on a damped bed of sand about 1 inch thick to get some water drainage and make it easyer to get the blocks even some type of curb or treated wood form around the outside edge will prevent the blocks from moveing out ward though iv seen patios and walk ways under light trafic never move much for years if as you say you have a fairly solid base to start the trick being not to trap water in the base if there is bad drainage cobble stone streets are the most enduring as are paving blocks if they have something to keep the edges from being pushed out and don't have to suffer from frezzing and thawing in water.


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