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re: Tying New Concrete to an Existing Foundation - Yes or No?
Posted on 6/24/14 at 1:31 pm to civiltiger07
Posted on 6/24/14 at 1:31 pm to civiltiger07
quote:
Looks like Shat! if you are covering it with something it not a problem. But the times I've seen this used it looks like you have hairy concrete.
But you sure can make a canoe out of is, amirite?
2
Posted on 6/24/14 at 1:39 pm to GulfCoastPoke
You are correct sir! But I wasn't on that team in school. I was on the steel bridge team.
Posted on 6/24/14 at 1:43 pm to GulfCoastPoke
It is a good bit more expensive. Like I said, it's if you don't want to mess with the mesh or worry about where the mesh is going to be. Another poster was correct that it does finish with some hairs in it. A water based stain from Home Depot or a rolled on coating takes care of the look - and frankly looks better anyway on a patio than bare concrete. But like I said, a lot of advice on here is overkill for what it is I think the OP is trying to do. What it boils down to is you can pay more money to get a good product, or put out a little more effort. Either way, the fiber or the wwm will be more than enough.
Posted on 6/24/14 at 1:44 pm to urinetrouble
quote:
Where are you getting this from?
When you load a concrete slab it will deflect. When this happens the top of the slab (in this case) will be under compression and the bottom will be in tension. Since you have tension on one half and compression on the other you have to get zero load somewhere. and that happens in the center. Concrete has awesome compressive strength and terrible tensile strength. That is why you use rebar in the bottom of a beam.
Back to the slab. While the tensile stresses of concrete is poor they it does have some tensile strength. So the slab you are talking about the designer probably determined that the slab did not need flexural reinforcement. The properties of the concrete were enough. However you always need some kind of temperature rebar to prevent cracking so he put some rebar in the center of the slab to do that.
no ifs ands or buts about it rebar at the center of a concrete member will not do anything to resist a flexural load.
Posted on 6/24/14 at 1:53 pm to civiltiger07
broom finish unless you want it to be slicker than owl shite when it rains.
Posted on 6/24/14 at 1:55 pm to civiltiger07
This is an OT home improvement project if i have ever read one
Bravo
Bravo
Posted on 6/24/14 at 1:59 pm to civiltiger07
quote:
Since you have tension on one half and compression on the other you have to get zero load somewhere. and that happens in the center.
Just no. Once the concrete cracks, the neutral axis will be not be at the center anymore. It will be closer to the top of the beam near Whitney's stress block. Any steel below that neutral axis will be effective in tension, including bars at the center.
quote:
That is why you use rebar in the bottom of a beam.
Bars at the bottom are more effective, but that doesn't mean bars at the center won't be engaged.
quote:
no ifs ands or buts about it rebar at the center of a concrete member will not do anything to resist a flexural load.
This is flat-out wrong. This is done in thin slabs all the time that need to resist both positive and negative bending.
Posted on 6/24/14 at 2:01 pm to civiltiger07
quote:
While the tensile stresses of concrete is poor they it does have some tensile strength. So the slab you are talking about the designer probably determined that the slab did not need flexural reinforcement. The properties of the concrete were enough.
This is not allowed by code for elevated free-spanning slabs, for good reason.
I hope you aren't designing structures.
Posted on 6/24/14 at 2:05 pm to civiltiger07
quote:
no ifs ands or buts about it rebar at the center of a concrete member will not do anything to resist a flexural load.
False
The location of the rebar just moves the location of the neutral axis
The compression block just becomes smaller
Posted on 6/24/14 at 2:07 pm to urinetrouble
i just did a 24x24 patio 4" thick tied into by carport and house slab on 2 sides myself. I used a hammer drill and put 12" pcs of rebar in the existing slab that tied into the new slab and put fiber in the new slab. Im not putting anything heavy on it, it is just for a bar and cooking area and is covered. It hasn't had any cracks yet.
Posted on 6/24/14 at 2:12 pm to AP83
give it a few years......it'll crack.
Posted on 6/24/14 at 2:13 pm to civiltiger07
quote:i'm sending these posts to professor okeil
civiltiger07
Posted on 6/24/14 at 2:22 pm to link
quote:
professor okeil
Yea he would be disappointed no doubt. I got a case of diarrhea of the mouth/keyboard. I will walk away now with my tail between my legs!
But I still would not use anything more than wire mesh for the patio slab.
Posted on 6/24/14 at 3:12 pm to AP83
I have a 20'x30' slab that was tied into my houses existing slab on two sides. It's been there for a few years and has no cracks. I also used the concrete that has the fiber in it. It was hairy at first but after a while the fibers that were on the surface went away.
When i was getting estimates for this every contractor i spoke with said it was better to tie it into the existing slab.
When i was getting estimates for this every contractor i spoke with said it was better to tie it into the existing slab.
Posted on 6/24/14 at 3:19 pm to ForeverLSU02
The only reason you should consider doweling a patio is if you think you might repurpose the space for indoor use in the future. Also, you would need a legit foundation to minimize settlement if you tie in.
Posted on 6/24/14 at 3:49 pm to ForeverLSU02
I recently poured a 700 sq ft patio slab and I connected it to the existing slab because I did it myself and it didn't cost that much extra to rent a hammer drill and buy the rebar and epoxy. I also put down wire mesh, even though people say that is not needed either. The stronger the concrete reinforcement, the better.
This post was edited on 6/24/14 at 3:53 pm
Posted on 6/24/14 at 4:03 pm to SmellslikeKevinBacon
quote:
When i was getting estimates for this every contractor i spoke with said it was better to tie it into the existing slab.
I said the same thing earlier in this thread. I would listen to the contractors who do this for a living over a bunch of civil engineering students.
Posted on 6/24/14 at 4:13 pm to Rohan
You mean the ones that came up with all of these methods that the contractors use?
The only advantage to tying to existing is to keep the top even with the house
Other than that, it's of no benefit to the patio
The only advantage to tying to existing is to keep the top even with the house
Other than that, it's of no benefit to the patio
Posted on 6/24/14 at 4:21 pm to Croacka
My patio will be about 6 inches lower than my slab and everyone I talked if said to tie it in. I freely admit I have no clue, but they have to be saying this for a reason.
Posted on 6/24/14 at 4:23 pm to Rohan
I'm not saying it won't work, I'm just saying I don't see the advantage
The concrete may shrink and develop a small gap between the two foundations, but I don't see how that's an issue
Maybe bc weeds will grow or bugs? Idk
The concrete may shrink and develop a small gap between the two foundations, but I don't see how that's an issue
Maybe bc weeds will grow or bugs? Idk
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