Opinions on Large Concrete Decks?

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snipped-for-privacy@gmail.com wrote:

Well, if it's off the ground on three sides, then I'd not worry about expansion problems crushing a foundation. Frankly, I'd prefer a concrete deck to one of wood or wood substitute. To keep it looking consistent with the railing, consider banding the concrete with whatever you use for the railing, such as Trex or another wood substitute. Also, consider having diamond sawed joints, such as every 6', instead of troweled in ones. They look neater, IMHO. I'd also consider using the fiberglass reinforced concrete and also look into air entrained concrete.
Sorry for the misunderstanding. When someone says concrete and deck in the same sentence, my mind automatically says that they really mean a patio.
Mark
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snipped-for-privacy@hotmail.com wrote:

Have just read a lot of newsgroup stuff about problems people have either from DIY jobs or poor contractor work. Not that funny, IMO.
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[/quote] Expansion joints are there to relieve stress from the concrete shrinking as it cures, not to stop pushing against the house, [quote]
They're called expansion joints because of what happens when the concrete expands without them.
I guarantee without enough room for expansion between the house and the slab - a poured wall will give in before a 30 ft slab will.
If you doubt things expand - have a look at this link.
http://sol.sci.uop.edu/~jfalward/temperatureandexpansion/temperatureandexpansion.html
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Hogwild wrote:

When concrete cures, the first thing it does, is it shrinks. Without expansion joints, the concrete will crack from that before anything else. That was where I was coming from. You are of course correct that it will expand and contract from temperature too and expansion joints are there to relieve that potential to crack too.
Now what does any of that have to do with your warning that"
"That much concrete will push against your house, even with expansion joints. "
All you have to do is have normal expansion joints, placed about 10 ft apart, like in any concrete pour. It has nothing to do with the fact that the OP wants a large patio and that somehow this means that it can't be done as normal, expansion joints.

http://sol.sci.uop.edu/~jfalward/temperatureandexpansion/temperatureandexpansion.html
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In case you were wondering, that link looked like a high school text book.
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If the poured concrete somehow gets below the expansion joint (as I have seen it do) it will come to rest against the house foundation.
When both the slab and the house expand in summer they will push together. They dont expand together. They are separate and expand separately. (just like the pictures in the link)
Unless the foundation wall has been designed strong enough to push the slab back the foundation wall will crack.
I am no concrete worker - but I do understand physics and have limited personal experience with both concrete patios and leaky basements. I'd rather not get into that.
As I said earlier, I agree a properly installed expansion joint should prevent the problem.
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On Thu, 16 Mar 2006 21:01:48 GMT, snipped-for-privacy@spam.invalid (Hogwild) wrote:

LOL! What kind of incompetent clowns did you hire?
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snipped-for-privacy@the.shoppe wrote:

The material is typically purchased in pre-cut 3-1/2" wide strips, since a 4" slab is typically formed with a 3-1/2" 2X4. Screeding the pea gravel is usually done before the strips are inserted, since the concrete is usually what holds them in place. My guess would be that about 95% of the pours have areas where the pea gravel is lower than the 3-1/2" strips either because of sagging in the middle of the screed board, failure to insert the strips fully or having them pushed up as the concrete is being poured or floated. It doesn't take much concrete-to-concrete contact to transfer the pressure directly to the foundation. All a good contractor would have to do would be to take his foot and make sure that there was pea gravel under the strips to prevent concrete from getting under them.
You are right about it being caused by poor workmanship, but that's just what happens in real life. The best way is to use gravel to separate the pours, when it comes to patios.
Mark
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Oh.
That sounds like a very nice deck. With all the engineering that will be required - I'm sure thermal expansion will be fully incorporated in the design.
IMO I think it would be better than a wood deck for a few reasons.
It will provide a rainproof area below.
No splinters. Low maintenance.
Good luck.
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