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Re: patio project
Wonderwarthog wrote:

Hi Ralph:
What they are doing is perfectly fine. I'm a Design Engineer, and a Union Carpenter now of more then 30 years, and a licensed Superintendent for this state of AZ. & Ia. for over 10 years. Is there a reason why you are questioning the expertease of the engineer?

Engineers don't live in the real world.
{Everything looks great on paper}.
Just kidding, of course....

Re: patio project

You can never be too cautious. Being extremely cautious has either given me peace of mind when I finally decided to go foward with a project or in a couple of cases, my persistance uncovered potential disasters. Money pits can lurk under stones unturned. I can't give you advice, except to cheer on your efforts to find a correct solution to your problem. My policy is to hold off until I feel totally comfortable with how the work will be done.

Re: patio project

I suggest you (nicely and respectfully) discuss your concerns with your contractor and just ask him/her why he/she is doing the project this way. Any good contractor should expect questions from their customers and should be willing to explain to you why they are doing the work this way. Also check with your local building inspector and ask if this is an acceptable method.

Re: patio project

Let's talk a bit about why expansion joints are used in the first place in concrete. Concrete is a rigid structure, and it doesn't have uniform strength. In compression ("pushing" force), it is extremely strong. But in tension ("pulling" force) it is quite weak--this is why people put steel reinforcement in the concrete---steel is strong in tension, and by the concrete adhering to the steel, it gets tensile strength from the steel. Now, let's say you didn't put any reinforcement steel of any kind in the concrete. Since all materials expand and contract with temperature, when the concrete expands, it is put into tension---so it cracks, because it is weak in tension. The control joints are to help the concrete crack in a controlled manner--they are intentionally made weaker, by making the concrete thinner in that particular spot, so that they hopefully will crack along that control joint. An expansion joint is basically a control joint, that is a bit wider, and is filled with some kind of easily compressable material, like felt or foam or whatever. If the space is wide enough, then the easily compressable material will take up the expansion without exerting too much force on the adjacent section---be it the next section of slab, adjacent wall, or foundation. Now, back to your patio---since the new concrete is a different structure from your house or wall, it will expand and contract at a different rate than your house or wall structure. This will cause compressive and tensile forces between the structures. Without an expansion joint between the structures, something has to give. The concrete will find its own joint regardless--it just may not be where you would like. But then again, it may crack right at the two structures (likely). Then the crack will widen over time with each expansion and contraction cycle, until it is wide enough to handle the worst case expansion. The reinforcement of the steel in your patio slab will help minimize the expansion of the slab--so, the slab itself will be less likely to crack. Note I said less likely--with concrete, there are no gaurantees, because unless the substrate has been done exactly right, the soil has been analysed for proper bearing capacity and compaction, etc., there are unknowns involved. For s simple patio, we don't spend that kind of money to do the careful analysis--it would be far too expensive relative to the overall project cost. Personally, I wouldn't worry too much about expansion joints, since most likely the cracks will form where you would put them anyway. But as someone else said, it is your house, your patio, your money---therefore, your rules. You want expansion joints, tell your contractor to put them in. He may charge more, because technically at this point it is a change order, but if it is important to you, then pay the money. Your house, your rules, and ultimately your responsibility---and you are the one who has to live with it. Good Luck!


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