Home>Discussions>EXTERIORS>confused about concrete in knoxville Tennessee?
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cali girl
confused about concrete in knoxville Tennessee?

I have been getting quotes from contractors here in Knoxville TN to create a larger patio... I am from sunny california so the rules here are different and our quotes have ranged from 3500 to 5200 huge difference.

we have a 12x12 in place now... we were just thinking of adding on to it... most contractors just said no problem... but I am concerned because one contractor said taking it out would be better because of the freezing weather and water would get between the old and new patio and freeze and crack.. others said they would just rebar it to the 12 x12 and it would be ok.. what would be the best thing to do rip it all out and start over or add on?:confused:

I have also found out that some are using a fiber mesh and not metal mesh. is there a difference? or is the technology of the fiber mesh as good as the metal?:confused:

then finally there is the question of attaching it to the home... do I need to worry about having the patio attached to the home with rebar or does it matter? can they just poor it to the house or do I need to worry about it separating and detaching from the home ?

I just do not know because of the freezing weather that we get here.. not to mention that it can rain one day and thee hours later it could freeze and snow.
I dont want to spend a lot but I also do not want it to look bad in one or two years. separate or crack.

the range in the bids are just so huge I need more info in order to choose someone.
any help on this would be great thanks!!!!:p

A. Spruce
Re: confused about concrete in knoxville Tennessee?

Being a Caliman myself, I can't say exactly what should be done in your new location. What I can tell you is this.

Concrete, in and of itself will expand and contract with temperature, which is why expansion joints are installed in slabs over about 10x10. The joint allows movement between slab sections in the case of a full separation, or a place for the slab to crack where it won't be seen as is the case with a surface seam. At any rate, one good freeze/heat cycle will have that slab cracked, which is going to allow moisture between and under the slab. So the guy telling you to replace the whole thing IMHO is only looking to get more money out of you.

Because of your climate, I would recommend pinning the new slab to the old and also pin it to the house. Pinning will allow movement without lifting, a hinge point if you will. Just so it's clear, pinning would be lengths of rebar that are drilled into the existing slab and house foundation that extend into the new slab.

The only place I've used reinforced concrete or reinforcing mesh is driveways and commercial patios where vehicles and/or heavy pedestrian loads are present. In the case of driveways, you want a thicker slab and the reinforcement to withstand the weight of vehicles. The reinforced concrete that I've used had fiberglass fiber mixed into it. I didn't like this because the fibers were left visible, sticking out of the surface which was unsightly and sharp which means bare feet were not allowed. I recently heard of horse hair being used as a reinforcing fiber, but I can't really see how that would work very well, quite frankly, though any exposed hair would wear away and not be a safety hazard.

If the bids have different levels of work or materials involved, then you don't have bids that you can compare based on price. Verify that each bid is for the exact same work, if it is, then choose the company you feel the most comfortable with as well as do the job you are looking for rather than the lowest price.

cali girl
Re: confused about concrete in knoxville Tennessee?

Thank you !!
This has been very helpful...... I am calling back one of the contractors to talk to him about his quote....

I am still not sure what the fiber in the concrete does. does that take the place of the wire mesh? do we need something like the fiber in the concrete?

I should make sure it is pined to the house and the existing patio, and make sure it has gravel under it at least 4 inches
any thing else I should make sure the patio has? or questions I should ask?

Thanks for all your help!!!!!!!!!

Leo Hake
Re: confused about concrete in knoxville Tennessee?

Patios, like sidewalks, tend to be about four inches thick. This is going to make it difficult to pin without breaking the existing patio. Doweling into your foundation is probably not a good idea. foundations are meant for minimal movement, whereas patios are expected to move. If you dowel into your house, you are locking that edge of the patio to the house. As the patio moves, that edge cannot, forcing a slope to the patio. Alright, as long as the patio only sinks.

Reinforcement in a patio, the same as with a sidewalk, foundation slab, driveway , street, or hiway, is for crack control, not strength. The strength of concrete poured on a base is from thickness, not reinforcement. The fibers distributed though the slab are meant to stop the microcracks as they form. Important in structural beams and columns. Not so much in a patio, though does have aesthetic value.

An expansion joint is needed between the house and the patio, typically half an inch. The other joints you see are contraction joints. Concrete shrinks as it ages. The idea is to make it crack where you want it, not where it wants.

The base is the essential element. With a proper base and good drainage, you will have minimal deflection between the old and the new patio.

If it were my project, I would start from scratch. Unless I knew what base was under the existing patio, of course. All new is the only way I could be confident in the base.

cali girl
Re: confused about concrete in knoxville Tennessee?

Thanks Leo,

I am learning more everyday. I think we are going to make our decision soon.... and with the information that I am receiving from this forum I think it will be a good decision...

I am just wondering about the fiber in the concrete... A. Spruce... said it hurt his feet.. but one of my contractors told me that all his patios have it and he has never heard anyone complain about it... so I am wondering if I should be worried about that... I want to walk on the patio barefoot!

Leo Hake
Re: confused about concrete in knoxville Tennessee?

Kinda confused by the fiber thing as well, but haven't messed with fiber reinforcement since college. Zeyad never mentioned fiberglass, but it is possible, I suppose. Think he worked with polyester and wire as fiber material.

Regardless, that is an issue material to the finish of the concrete. Which is another consideration you have. If you are concerned about matching the old with the new then you may not be happy with the end result if you salvage existing. We have exposed aggregate. Very difficult to match. Smooth, gray, not as tough, but still not going to be perfect. Depends on what you want.

cali girl
Re: confused about concrete in knoxville Tennessee?

Thank Leo! I appreciate your advice..

I have another issue that just came up.....
after I picked my contractor, ( he has all the paperwork good price and I was able to talk to him without issue) he started looking at the side of my yard and is worried that there might not be enough of a grade to make the concrete have proper runoff..

I am a bit worried about this too.. any suggestions to what to do on this.
this link shows photos

A. Spruce
Re: confused about concrete in knoxville Tennessee?

It doesn't take much slope to get drainage away from the house, as little as 1/8" per foot will work, though 1/4" or more is better. Assuming a walkway along the house, I'd install a drain line down the outside of the walkway and plumb both the downspouts and a few surface receptacles in. Another alternative would be to run either a drain channel in the surface of the concrete or install something along the lines of a Deco-drain.

As for hitting utilities, they should have had the utilities marked by a company that specializes in locating and marking underground things before digging. This service is usually free and its very existence is to prevent damage to utilities and the expense that can be incurred.

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