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redhermes 11-14-2008 08:49 PM

Concrete Patio Extension
 
I live in Tempe AZ, summer temperatures are always over 100 (Fahrenheit) and winters are mild, average minimum is 39 degrees Fahrenheit. Every few years we get a freeze. Average rainfall is only 9 inches per year.

I have a structurally sound 12 year old concrete patio (125 sq feet, 6 inches slab). I want to add a 350 sq foot extension.

I am getting conflicting advice from the local contractors. Some say I have to completely tear out the old slab. Others say they can add on to it but donít agree if the two slabs should be physically connected.

I plan to cover the combined patio with a redwood deck. I also plan to put up a pergola over part of the patio. Finally the extension is going to be added to an area of the yard that was just filled in (it was a swimming pool).

Please help me to spec out a sound concrete extension. If this was your project how would you describe the work to be completed?

Thanks in advance for your help.

iMisspell 11-14-2008 11:37 PM

Quote:

Originally Posted by redhermes (Post 185039)
Finally the extension is going to be added to an area of the yard that was just filled in (it was a swimming pool).

Below ground pool ?

I know little about this, but just recently ive talked with 8-10 masons and excavators and they all pretty much said the same thing that, mother nature is the best source for compacting the ground, but with only 9" of rain, i guess she will not be able to help you too much.

If the pool was below ground, personally i would be concerind with the ground settling and causing problems with the new concrete.

If you are covering your old patio, why are you concerned with it at all ?

_

redhermes 11-15-2008 08:56 AM

Hi iMisspell, thanks for replying.

The pool was in-ground (is there any other kind ;-0).

My concern is that if the subgrade is not correctly prepared/compacted the patio will either cant to one side or crack excessively due to settling.

I hope someone can tell me something like, "oh, you need 4 inches of ABC compacted to x degree.

Bob


Quote:

Originally Posted by iMisspell (Post 185103)
Below ground pool ?

I know little about this, but just recently ive talked with 8-10 masons and excavators and they all pretty much said the same thing that, mother nature is the best source for compacting the ground, but with only 9" of rain, i guess she will not be able to help you too much.

If the pool was below ground, personally i would be concerind with the ground settling and causing problems with the new concrete.

If you are covering your old patio, why are you concerned with it at all ?

_


CrpntrFrk 11-15-2008 09:03 AM

Hey Red,
You might be able to conect the two slabs if the earth was compacted correctly! A compaction test might be in order especially if something as deep as a pool was filled in! Where are you in Tempe? I live in Globe and might be able to take a look. Another thing you might want to consider is the inspector. What does he/she say about the situation?

redhermes 11-15-2008 11:49 PM

Hi CrpntrFrk

I was hoping I could just put down a few inches of paver base and compact it... I'm only planning on the deck a small pergola, not really that much weight is it?

Thanks

Quote:

Originally Posted by CrpntrFrk (Post 185216)
Hey Red,
You might be able to conect the two slabs if the earth was compacted correctly! A compaction test might be in order especially if something as deep as a pool was filled in! Where are you in Tempe? I live in Globe and might be able to take a look. Another thing you might want to consider is the inspector. What does he/she say about the situation?


iMisspell 11-16-2008 12:51 AM

Quote:

Originally Posted by redhermes (Post 185214)
The pool was in-ground (is there any other kind ;-0).

Guess different parts of the country have different things...
Growing up my parents had an above ground pool 18'-20' in diameter 4 foot deep and it sat in the ground about 8".
Big difference in filling a 8"x20' hole and a 10'-15'x30' hole.

Noting what the hole was filled with might help people get a better picture of your set up; gravel, shale, loose dirt, clay, large rock and dirt, etc.

_

redhermes 11-17-2008 05:50 PM

Any suggestion from the resident experts?
 
Any help is appreciated!

CrpntrFrk 11-17-2008 06:14 PM

Quote:

Originally Posted by redhermes (Post 185637)
Hi CrpntrFrk

I was hoping I could just put down a few inches of paver base and compact it... I'm only planning on the deck a small pergola, not really that much weight is it?

Thanks

It might not be that much weight but if a good rain were to come and wash under the paver base then it would settle and tweak the structure! It is just better to do it right then to have to fix it later!

redhermes 11-17-2008 07:15 PM

A very good point... so are you saying that before I proceed with the project, I need to get a soil compaction test?


Quote:

Originally Posted by CrpntrFrk (Post 186506)
It might not be that much weight but if a good rain were to come and wash under the paver base then it would settle and tweak the structure! It is just better to do it right then to have to fix it later!


CrpntrFrk 11-17-2008 07:26 PM

Quote:

Originally Posted by redhermes (Post 186531)
A very good point... so are you saying that before I proceed with the project, I need to get a soil compaction test?

Well if you were not a part of the filling in then it might not be a bad idea. If you were a part of it then ask yourself these questions.
Was it filled with a good compactable soil?
Was it installed in 12"-14" lifts then compacted each time?
Was water used to help compact?
What type of compactor was used? The level of lifts may vary depending on the compactor.
If the answer is yes to those questions then it should be ok!

joed 11-17-2008 07:36 PM

Tear it all out and build the redwood deck without the patio underneath.

buletbob 11-18-2008 06:53 AM

You could build over the filled in pool, But I would get rid of expanding the cement patio. when you build the red wood deck any supporting posts must be dug down to virgin soil, so if you were to sink a sonotube down to that depth of the old pool you would be fine, and not have to worry about the deck sinking. BOB

Marvin Gardens 11-18-2008 08:43 AM

If the pool were out of the equation then I would say to add on to the existing slab using rebar to connect it with the new slab.

But the filled in pool area raises a lot of red flags.

Bottom line is that it will settle over the years and there is no way to know how much or how even it will settle.

Your slab could crack and shift in a matter of a few years and all the money you put into it would be gone. There would be no way to repair it and it would just have to be torn out and redone.

You could do things like pour deep footers to get to solid ground, wait till the soil settles before you build, get a compactor in there to make it happen now, and other ideas I can't think of right now.

As is sits now there is no way I would be building anything over that until it stabilizes.

redhermes 11-18-2008 07:49 PM

Marvin, Bob, Joe and CrpntrFrk Thanks!
 
Okay, I get it. Extending the patio for the deck is not a good plan.

The collective wisdom seems to be the safest/smartest plan is tear out the existing patio and build a conventional deck with concrete piers and footers that set below the level of the pool.

Does that sound about right...

Thank for the suggestions.

Marvin Gardens 11-18-2008 10:09 PM

Quote:

Originally Posted by redhermes (Post 187044)
Okay, I get it. Extending the patio for the deck is not a good plan.

The collective wisdom seems to be the safest/smartest plan is tear out the existing patio and build a conventional deck with concrete piers and footers that set below the level of the pool.

Does that sound about right...

Thank for the suggestions.

I think this is the safest option. You will have to make sure that each support has been tamped down or you end up with a pier block sinking and your deck sagging.


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